Merge tag 'wq-for-6.6' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq

Pull workqueue updates from Tejun Heo:

 - Unbound workqueues now support more flexible affinity scopes.

   The default behavior is to soft-affine according to last level cache
   boundaries. A work item queued from a given LLC is executed by a
   worker running on the same LLC but the worker may be moved across
   cache boundaries as the scheduler sees fit. On machines which
   multiple L3 caches, which are becoming more popular along with
   chiplet designs, this improves cache locality while not harming work
   conservation too much.

   Unbound workqueues are now also a lot more flexible in terms of
   execution affinity. Differeing levels of affinity scopes are
   supported and both the default and per-workqueue affinity settings
   can be modified dynamically. This should help working around amny of
   sub-optimal behaviors observed recently with asymmetric ARM CPUs.

   This involved signficant restructuring of workqueue code. Nothing was
   reported yet but there's some risk of subtle regressions. Should keep
   an eye out.

 - Rescuer workers now has more identifiable comms.

 - workqueue.unbound_cpus added so that CPUs which can be used by
   workqueue can be constrained early during boot.

 - Now that all the in-tree users have been flushed out, trigger warning
   if system-wide workqueues are flushed.

* tag 'wq-for-6.6' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq: (31 commits)
  workqueue: fix data race with the pwq->stats[] increment
  workqueue: Rename rescuer kworker
  workqueue: Make default affinity_scope dynamically updatable
  workqueue: Add "Affinity Scopes and Performance" section to documentation
  workqueue: Implement non-strict affinity scope for unbound workqueues
  workqueue: Add workqueue_attrs->__pod_cpumask
  workqueue: Factor out need_more_worker() check and worker wake-up
  workqueue: Factor out work to worker assignment and collision handling
  workqueue: Add multiple affinity scopes and interface to select them
  workqueue: Modularize wq_pod_type initialization
  workqueue: Add tools/workqueue/wq_dump.py which prints out workqueue configuration
  workqueue: Generalize unbound CPU pods
  workqueue: Factor out clearing of workqueue-only attrs fields
  workqueue: Factor out actual cpumask calculation to reduce subtlety in wq_update_pod()
  workqueue: Initialize unbound CPU pods later in the boot
  workqueue: Move wq_pod_init() below workqueue_init()
  workqueue: Rename NUMA related names to use pod instead
  workqueue: Rename workqueue_attrs->no_numa to ->ordered
  workqueue: Make unbound workqueues to use per-cpu pool_workqueues
  workqueue: Call wq_update_unbound_numa() on all CPUs in NUMA node on CPU hotplug
  ...

Documentation/admin-guide/kernel-parameters.txt

@@ -7076,6 +7076,13 @@
 			disables both lockup detectors. Default is 10
 			seconds.
 
+	workqueue.unbound_cpus=
+			[KNL,SMP] Specify to constrain one or some CPUs
+			to use in unbound workqueues.
+			Format: <cpu-list>
+			By default, all online CPUs are available for
+			unbound workqueues.
+
 	workqueue.watchdog_thresh=
 			If CONFIG_WQ_WATCHDOG is configured, workqueue can
 			warn stall conditions and dump internal state to
@@ -7097,15 +7104,6 @@
 			threshold repeatedly. They are likely good
 			candidates for using WQ_UNBOUND workqueues instead.
 
-	workqueue.disable_numa
-			By default, all work items queued to unbound
-			workqueues are affine to the NUMA nodes they're
-			issued on, which results in better behavior in
-			general.  If NUMA affinity needs to be disabled for
-			whatever reason, this option can be used.  Note
-			that this also can be controlled per-workqueue for
-			workqueues visible under /sys/bus/workqueue/.
-
 	workqueue.power_efficient
 			Per-cpu workqueues are generally preferred because
 			they show better performance thanks to cache
@@ -7121,6 +7119,18 @@
 			The default value of this parameter is determined by
 			the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
 
+        workqueue.default_affinity_scope=
+			Select the default affinity scope to use for unbound
+			workqueues. Can be one of "cpu", "smt", "cache",
+			"numa" and "system". Default is "cache". For more
+			information, see the Affinity Scopes section in
+			Documentation/core-api/workqueue.rst.
+
+			This can be changed after boot by writing to the
+			matching /sys/module/workqueue/parameters file. All
+			workqueues with the "default" affinity scope will be
+			updated accordignly.
+
 	workqueue.debug_force_rr_cpu
 			Workqueue used to implicitly guarantee that work
 			items queued without explicit CPU specified are put

Documentation/core-api/workqueue.rst

-====================================
-Concurrency Managed Workqueue (cmwq)
-====================================
+=========
+Workqueue
+=========
 
 :Date: September, 2010
 :Author: Tejun Heo <tj@kernel.org>
@@ -25,8 +25,8 @@ there is no work item left on the workqueue the worker becomes idle.
 When a new work item gets queued, the worker begins executing again.
 
 
-Why cmwq?
-=========
+Why Concurrency Managed Workqueue?
+==================================
 
 In the original wq implementation, a multi threaded (MT) wq had one
 worker thread per CPU and a single threaded (ST) wq had one worker
@@ -220,17 +220,16 @@ resources, scheduled and executed.
 ``max_active``
 --------------
 
-``@max_active`` determines the maximum number of execution contexts
-per CPU which can be assigned to the work items of a wq.  For example,
-with ``@max_active`` of 16, at most 16 work items of the wq can be
-executing at the same time per CPU.
+``@max_active`` determines the maximum number of execution contexts per
+CPU which can be assigned to the work items of a wq. For example, with
+``@max_active`` of 16, at most 16 work items of the wq can be executing
+at the same time per CPU. This is always a per-CPU attribute, even for
+unbound workqueues.
 
-Currently, for a bound wq, the maximum limit for ``@max_active`` is
-512 and the default value used when 0 is specified is 256.  For an
-unbound wq, the limit is higher of 512 and 4 *
-``num_possible_cpus()``.  These values are chosen sufficiently high
-such that they are not the limiting factor while providing protection
-in runaway cases.
+The maximum limit for ``@max_active`` is 512 and the default value used
+when 0 is specified is 256. These values are chosen sufficiently high
+such that they are not the limiting factor while providing protection in
+runaway cases.
 
 The number of active work items of a wq is usually regulated by the
 users of the wq, more specifically, by how many work items the users
@@ -348,27 +347,346 @@ Guidelines
   level of locality in wq operations and work item execution.
 
 
+Affinity Scopes
+===============
+
+An unbound workqueue groups CPUs according to its affinity scope to improve
+cache locality. For example, if a workqueue is using the default affinity
+scope of "cache", it will group CPUs according to last level cache
+boundaries. A work item queued on the workqueue will be assigned to a worker
+on one of the CPUs which share the last level cache with the issuing CPU.
+Once started, the worker may or may not be allowed to move outside the scope
+depending on the ``affinity_strict`` setting of the scope.
+
+Workqueue currently supports the following affinity scopes.
+
+``default``
+  Use the scope in module parameter ``workqueue.default_affinity_scope``
+  which is always set to one of the scopes below.
+
+``cpu``
+  CPUs are not grouped. A work item issued on one CPU is processed by a
+  worker on the same CPU. This makes unbound workqueues behave as per-cpu
+  workqueues without concurrency management.
+
+``smt``
+  CPUs are grouped according to SMT boundaries. This usually means that the
+  logical threads of each physical CPU core are grouped together.
+
+``cache``
+  CPUs are grouped according to cache boundaries. Which specific cache
+  boundary is used is determined by the arch code. L3 is used in a lot of
+  cases. This is the default affinity scope.
+
+``numa``
+  CPUs are grouped according to NUMA bounaries.
+
+``system``
+  All CPUs are put in the same group. Workqueue makes no effort to process a
+  work item on a CPU close to the issuing CPU.
+
+The default affinity scope can be changed with the module parameter
+``workqueue.default_affinity_scope`` and a specific workqueue's affinity
+scope can be changed using ``apply_workqueue_attrs()``.
+
+If ``WQ_SYSFS`` is set, the workqueue will have the following affinity scope
+related interface files under its ``/sys/devices/virtual/WQ_NAME/``
+directory.
+
+``affinity_scope``
+  Read to see the current affinity scope. Write to change.
+
+  When default is the current scope, reading this file will also show the
+  current effective scope in parentheses, for example, ``default (cache)``.
+
+``affinity_strict``
+  0 by default indicating that affinity scopes are not strict. When a work
+  item starts execution, workqueue makes a best-effort attempt to ensure
+  that the worker is inside its affinity scope, which is called
+  repatriation. Once started, the scheduler is free to move the worker
+  anywhere in the system as it sees fit. This enables benefiting from scope
+  locality while still being able to utilize other CPUs if necessary and
+  available.
+
+  If set to 1, all workers of the scope are guaranteed always to be in the
+  scope. This may be useful when crossing affinity scopes has other
+  implications, for example, in terms of power consumption or workload
+  isolation. Strict NUMA scope can also be used to match the workqueue
+  behavior of older kernels.
+
+
+Affinity Scopes and Performance
+===============================
+
+It'd be ideal if an unbound workqueue's behavior is optimal for vast
+majority of use cases without further tuning. Unfortunately, in the current
+kernel, there exists a pronounced trade-off between locality and utilization
+necessitating explicit configurations when workqueues are heavily used.
+
+Higher locality leads to higher efficiency where more work is performed for
+the same number of consumed CPU cycles. However, higher locality may also
+cause lower overall system utilization if the work items are not spread
+enough across the affinity scopes by the issuers. The following performance
+testing with dm-crypt clearly illustrates this trade-off.
+
+The tests are run on a CPU with 12-cores/24-threads split across four L3
+caches (AMD Ryzen 9 3900x). CPU clock boost is turned off for consistency.
+``/dev/dm-0`` is a dm-crypt device created on NVME SSD (Samsung 990 PRO) and
+opened with ``cryptsetup`` with default settings.
+
+
+Scenario 1: Enough issuers and work spread across the machine
+-------------------------------------------------------------
+
+The command used: ::
+
+  $ fio --filename=/dev/dm-0 --direct=1 --rw=randrw --bs=32k --ioengine=libaio \
+    --iodepth=64 --runtime=60 --numjobs=24 --time_based --group_reporting \
+    --name=iops-test-job --verify=sha512
+
+There are 24 issuers, each issuing 64 IOs concurrently. ``--verify=sha512``
+makes ``fio`` generate and read back the content each time which makes
+execution locality matter between the issuer and ``kcryptd``. The followings
+are the read bandwidths and CPU utilizations depending on different affinity
+scope settings on ``kcryptd`` measured over five runs. Bandwidths are in
+MiBps, and CPU util in percents.
+
+.. list-table::
+   :widths: 16 20 20
+   :header-rows: 1
+
+   * - Affinity
+     - Bandwidth (MiBps)
+     - CPU util (%)
+
+   * - system
+     - 1159.40 ±1.34
+     - 99.31 ±0.02
+
+   * - cache
+     - 1166.40 ±0.89
+     - 99.34 ±0.01
+
+   * - cache (strict)
+     - 1166.00 ±0.71
+     - 99.35 ±0.01
+
+With enough issuers spread across the system, there is no downside to
+"cache", strict or otherwise. All three configurations saturate the whole
+machine but the cache-affine ones outperform by 0.6% thanks to improved
+locality.
+
+
+Scenario 2: Fewer issuers, enough work for saturation
+-----------------------------------------------------
+
+The command used: ::
+
+  $ fio --filename=/dev/dm-0 --direct=1 --rw=randrw --bs=32k \
+    --ioengine=libaio --iodepth=64 --runtime=60 --numjobs=8 \
+    --time_based --group_reporting --name=iops-test-job --verify=sha512
+
+The only difference from the previous scenario is ``--numjobs=8``. There are
+a third of the issuers but is still enough total work to saturate the
+system.
+
+.. list-table::
+   :widths: 16 20 20
+   :header-rows: 1
+
+   * - Affinity
+     - Bandwidth (MiBps)
+     - CPU util (%)
+
+   * - system
+     - 1155.40 ±0.89
+     - 97.41 ±0.05
+
+   * - cache
+     - 1154.40 ±1.14
+     - 96.15 ±0.09
+
+   * - cache (strict)
+     - 1112.00 ±4.64
+     - 93.26 ±0.35
+
+This is more than enough work to saturate the system. Both "system" and
+"cache" are nearly saturating the machine but not fully. "cache" is using
+less CPU but the better efficiency puts it at the same bandwidth as
+"system".
+
+Eight issuers moving around over four L3 cache scope still allow "cache
+(strict)" to mostly saturate the machine but the loss of work conservation
+is now starting to hurt with 3.7% bandwidth loss.
+
+
+Scenario 3: Even fewer issuers, not enough work to saturate
+-----------------------------------------------------------
+
+The command used: ::
+
+  $ fio --filename=/dev/dm-0 --direct=1 --rw=randrw --bs=32k \
+    --ioengine=libaio --iodepth=64 --runtime=60 --numjobs=4 \
+    --time_based --group_reporting --name=iops-test-job --verify=sha512
+
+Again, the only difference is ``--numjobs=4``. With the number of issuers
+reduced to four, there now isn't enough work to saturate the whole system
+and the bandwidth becomes dependent on completion latencies.
+
+.. list-table::
+   :widths: 16 20 20
+   :header-rows: 1
+
+   * - Affinity
+     - Bandwidth (MiBps)
+     - CPU util (%)
+
+   * - system
+     - 993.60 ±1.82
+     - 75.49 ±0.06
+
+   * - cache
+     - 973.40 ±1.52
+     - 74.90 ±0.07
+
+   * - cache (strict)
+     - 828.20 ±4.49
+     - 66.84 ±0.29
+
+Now, the tradeoff between locality and utilization is clearer. "cache" shows
+2% bandwidth loss compared to "system" and "cache (struct)" whopping 20%.
+
+
+Conclusion and Recommendations
+------------------------------
+
+In the above experiments, the efficiency advantage of the "cache" affinity
+scope over "system" is, while consistent and noticeable, small. However, the
+impact is dependent on the distances between the scopes and may be more
+pronounced in processors with more complex topologies.
+
+While the loss of work-conservation in certain scenarios hurts, it is a lot
+better than "cache (strict)" and maximizing workqueue utilization is
+unlikely to be the common case anyway. As such, "cache" is the default
+affinity scope for unbound pools.
+
+* As there is no one option which is great for most cases, workqueue usages
+  that may consume a significant amount of CPU are recommended to configure
+  the workqueues using ``apply_workqueue_attrs()`` and/or enable
+  ``WQ_SYSFS``.
+
+* An unbound workqueue with strict "cpu" affinity scope behaves the same as
+  ``WQ_CPU_INTENSIVE`` per-cpu workqueue. There is no real advanage to the
+  latter and an unbound workqueue provides a lot more flexibility.
+
+* Affinity scopes are introduced in Linux v6.5. To emulate the previous
+  behavior, use strict "numa" affinity scope.
+
+* The loss of work-conservation in non-strict affinity scopes is likely
+  originating from the scheduler. There is no theoretical reason why the
+  kernel wouldn't be able to do the right thing and maintain
+  work-conservation in most cases. As such, it is possible that future
+  scheduler improvements may make most of these tunables unnecessary.
+
+
+Examining Configuration
+=======================
+
+Use tools/workqueue/wq_dump.py to examine unbound CPU affinity
+configuration, worker pools and how workqueues map to the pools: ::
+
+  $ tools/workqueue/wq_dump.py
+  Affinity Scopes
+  ===============
+  wq_unbound_cpumask=0000000f
+
+  CPU
+    nr_pods  4
+    pod_cpus [0]=00000001 [1]=00000002 [2]=00000004 [3]=00000008
+    pod_node [0]=0 [1]=0 [2]=1 [3]=1
+    cpu_pod  [0]=0 [1]=1 [2]=2 [3]=3
+
+  SMT
+    nr_pods  4
+    pod_cpus [0]=00000001 [1]=00000002 [2]=00000004 [3]=00000008
+    pod_node [0]=0 [1]=0 [2]=1 [3]=1
+    cpu_pod  [0]=0 [1]=1 [2]=2 [3]=3
+
+  CACHE (default)
+    nr_pods  2
+    pod_cpus [0]=00000003 [1]=0000000c
+    pod_node [0]=0 [1]=1
+    cpu_pod  [0]=0 [1]=0 [2]=1 [3]=1
+
+  NUMA
+    nr_pods  2
+    pod_cpus [0]=00000003 [1]=0000000c
+    pod_node [0]=0 [1]=1
+    cpu_pod  [0]=0 [1]=0 [2]=1 [3]=1
+
+  SYSTEM
+    nr_pods  1
+    pod_cpus [0]=0000000f
+    pod_node [0]=-1
+    cpu_pod  [0]=0 [1]=0 [2]=0 [3]=0
+
+  Worker Pools
+  ============
+  pool[00] ref= 1 nice=  0 idle/workers=  4/  4 cpu=  0
+  pool[01] ref= 1 nice=-20 idle/workers=  2/  2 cpu=  0
+  pool[02] ref= 1 nice=  0 idle/workers=  4/  4 cpu=  1
+  pool[03] ref= 1 nice=-20 idle/workers=  2/  2 cpu=  1
+  pool[04] ref= 1 nice=  0 idle/workers=  4/  4 cpu=  2
+  pool[05] ref= 1 nice=-20 idle/workers=  2/  2 cpu=  2
+  pool[06] ref= 1 nice=  0 idle/workers=  3/  3 cpu=  3
+  pool[07] ref= 1 nice=-20 idle/workers=  2/  2 cpu=  3
+  pool[08] ref=42 nice=  0 idle/workers=  6/  6 cpus=0000000f
+  pool[09] ref=28 nice=  0 idle/workers=  3/  3 cpus=00000003
+  pool[10] ref=28 nice=  0 idle/workers= 17/ 17 cpus=0000000c
+  pool[11] ref= 1 nice=-20 idle/workers=  1/  1 cpus=0000000f
+  pool[12] ref= 2 nice=-20 idle/workers=  1/  1 cpus=00000003
+  pool[13] ref= 2 nice=-20 idle/workers=  1/  1 cpus=0000000c
+
+  Workqueue CPU -> pool
+  =====================
+  [    workqueue \ CPU              0  1  2  3 dfl]
+  events                   percpu   0  2  4  6
+  events_highpri           percpu   1  3  5  7
+  events_long              percpu   0  2  4  6
+  events_unbound           unbound  9  9 10 10  8
+  events_freezable         percpu   0  2  4  6
+  events_power_efficient   percpu   0  2  4  6
+  events_freezable_power_  percpu   0  2  4  6
+  rcu_gp                   percpu   0  2  4  6
+  rcu_par_gp               percpu   0  2  4  6
+  slub_flushwq             percpu   0  2  4  6
+  netns                    ordered  8  8  8  8  8
+  ...
+
+See the command's help message for more info.
+
+
 Monitoring
 ==========
 
 Use tools/workqueue/wq_monitor.py to monitor workqueue operations: ::
 
   $ tools/workqueue/wq_monitor.py events
-                              total  infl  CPUtime  CPUhog  CMwake  mayday rescued
+                              total  infl  CPUtime  CPUhog CMW/RPR  mayday rescued
   events                      18545     0      6.1       0       5       -       -
   events_highpri                  8     0      0.0       0       0       -       -
   events_long                     3     0      0.0       0       0       -       -
-  events_unbound              38306     0      0.1       -       -       -       -
+  events_unbound              38306     0      0.1       -       7       -       -
   events_freezable                0     0      0.0       0       0       -       -
   events_power_efficient      29598     0      0.2       0       0       -       -
   events_freezable_power_        10     0      0.0       0       0       -       -
   sock_diag_events                0     0      0.0       0       0       -       -
 
-                              total  infl  CPUtime  CPUhog  CMwake  mayday rescued
+                              total  infl  CPUtime  CPUhog CMW/RPR  mayday rescued
   events                      18548     0      6.1       0       5       -       -
   events_highpri                  8     0      0.0       0       0       -       -
   events_long                     3     0      0.0       0       0       -       -
-  events_unbound              38322     0      0.1       -       -       -       -
+  events_unbound              38322     0      0.1       -       7       -       -
   events_freezable                0     0      0.0       0       0       -       -
   events_power_efficient      29603     0      0.2       0       0       -       -
   events_freezable_power_        10     0      0.0       0       0       -       -

include/linux/workqueue.h

@@ -125,6 +125,17 @@ struct rcu_work {
 	struct workqueue_struct *wq;
 };
 
+enum wq_affn_scope {
+	WQ_AFFN_DFL,			/* use system default */
+	WQ_AFFN_CPU,			/* one pod per CPU */
+	WQ_AFFN_SMT,			/* one pod poer SMT */
+	WQ_AFFN_CACHE,			/* one pod per LLC */
+	WQ_AFFN_NUMA,			/* one pod per NUMA node */
+	WQ_AFFN_SYSTEM,			/* one pod across the whole system */
+
+	WQ_AFFN_NR_TYPES,
+};
+
 /**
  * struct workqueue_attrs - A struct for workqueue attributes.
  *
@@ -138,17 +149,58 @@ struct workqueue_attrs {
 
 	/**
 	 * @cpumask: allowed CPUs
+	 *
+	 * Work items in this workqueue are affine to these CPUs and not allowed
+	 * to execute on other CPUs. A pool serving a workqueue must have the
+	 * same @cpumask.
 	 */
 	cpumask_var_t cpumask;
 
 	/**
-	 * @no_numa: disable NUMA affinity
+	 * @__pod_cpumask: internal attribute used to create per-pod pools
+	 *
+	 * Internal use only.
+	 *
+	 * Per-pod unbound worker pools are used to improve locality. Always a
+	 * subset of ->cpumask. A workqueue can be associated with multiple
+	 * worker pools with disjoint @__pod_cpumask's. Whether the enforcement
+	 * of a pool's @__pod_cpumask is strict depends on @affn_strict.
+	 */
+	cpumask_var_t __pod_cpumask;
+
+	/**
+	 * @affn_strict: affinity scope is strict
 	 *
-	 * Unlike other fields, ``no_numa`` isn't a property of a worker_pool. It
-	 * only modifies how :c:func:`apply_workqueue_attrs` select pools and thus
-	 * doesn't participate in pool hash calculations or equality comparisons.
+	 * If clear, workqueue will make a best-effort attempt at starting the
+	 * worker inside @__pod_cpumask but the scheduler is free to migrate it
+	 * outside.
+	 *
+	 * If set, workers are only allowed to run inside @__pod_cpumask.
+	 */
+	bool affn_strict;
+
+	/*
+	 * Below fields aren't properties of a worker_pool. They only modify how
+	 * :c:func:`apply_workqueue_attrs` select pools and thus don't
+	 * participate in pool hash calculations or equality comparisons.
+	 */
+
+	/**
+	 * @affn_scope: unbound CPU affinity scope
+	 *
+	 * CPU pods are used to improve execution locality of unbound work
+	 * items. There are multiple pod types, one for each wq_affn_scope, and
+	 * every CPU in the system belongs to one pod in every pod type. CPUs
+	 * that belong to the same pod share the worker pool. For example,
+	 * selecting %WQ_AFFN_NUMA makes the workqueue use a separate worker
+	 * pool for each NUMA node.
+	 */
+	enum wq_affn_scope affn_scope;
+
+	/**
+	 * @ordered: work items must be executed one by one in queueing order
 	 */
-	bool no_numa;
+	bool ordered;
 };
 
 static inline struct delayed_work *to_delayed_work(struct work_struct *work)
@@ -343,14 +395,10 @@ enum {
 	__WQ_ORDERED_EXPLICIT	= 1 << 19, /* internal: alloc_ordered_workqueue() */
 
 	WQ_MAX_ACTIVE		= 512,	  /* I like 512, better ideas? */
-	WQ_MAX_UNBOUND_PER_CPU	= 4,	  /* 4 * #cpus for unbound wq */
+	WQ_UNBOUND_MAX_ACTIVE	= WQ_MAX_ACTIVE,
 	WQ_DFL_ACTIVE		= WQ_MAX_ACTIVE / 2,
 };
 
-/* unbound wq's aren't per-cpu, scale max_active according to #cpus */
-#define WQ_UNBOUND_MAX_ACTIVE	\
-	max_t(int, WQ_MAX_ACTIVE, num_possible_cpus() * WQ_MAX_UNBOUND_PER_CPU)
-
 /*
  * System-wide workqueues which are always present.
  *
@@ -391,7 +439,7 @@ extern struct workqueue_struct *system_freezable_power_efficient_wq;
  * alloc_workqueue - allocate a workqueue
  * @fmt: printf format for the name of the workqueue
  * @flags: WQ_* flags
- * @max_active: max in-flight work items, 0 for default
+ * @max_active: max in-flight work items per CPU, 0 for default
  * remaining args: args for @fmt
  *
  * Allocate a workqueue with the specified parameters.  For detailed
@@ -569,6 +617,7 @@ static inline bool schedule_work(struct work_struct *work)
 
 /*
  * Detect attempt to flush system-wide workqueues at compile time when possible.
+ * Warn attempt to flush system-wide workqueues at runtime.
  *
  * See https://lkml.kernel.org/r/49925af7-78a8-a3dd-bce6-cfc02e1a9236@I-love.SAKURA.ne.jp
  * for reasons and steps for converting system-wide workqueues into local workqueues.
@@ -576,52 +625,13 @@ static inline bool schedule_work(struct work_struct *work)
 extern void __warn_flushing_systemwide_wq(void)
 	__compiletime_warning("Please avoid flushing system-wide workqueues.");
 
-/**
- * flush_scheduled_work - ensure that any scheduled work has run to completion.
- *
- * Forces execution of the kernel-global workqueue and blocks until its
- * completion.
- *
- * It's very easy to get into trouble if you don't take great care.
- * Either of the following situations will lead to deadlock:
- *
- *	One of the work items currently on the workqueue needs to acquire
- *	a lock held by your code or its caller.
- *
- *	Your code is running in the context of a work routine.
- *
- * They will be detected by lockdep when they occur, but the first might not
- * occur very often.  It depends on what work items are on the workqueue and
- * what locks they need, which you have no control over.
- *
- * In most situations flushing the entire workqueue is overkill; you merely
- * need to know that a particular work item isn't queued and isn't running.
- * In such cases you should use cancel_delayed_work_sync() or
- * cancel_work_sync() instead.
- *
- * Please stop calling this function! A conversion to stop flushing system-wide
- * workqueues is in progress. This function will be removed after all in-tree
- * users stopped calling this function.
- */
-/*
- * The background of commit 771c035372a036f8 ("deprecate the
- * '__deprecated' attribute warnings entirely and for good") is that,
- * since Linus builds all modules between every single pull he does,
- * the standard kernel build needs to be _clean_ in order to be able to
- * notice when new problems happen. Therefore, don't emit warning while
- * there are in-tree users.
- */
+/* Please stop using this function, for this function will be removed in near future. */
 #define flush_scheduled_work()						\
 ({									\
-	if (0)								\
 	__warn_flushing_systemwide_wq();				\
 	__flush_workqueue(system_wq);					\
 })
 
-/*
- * Although there is no longer in-tree caller, for now just emit warning
- * in order to give out-of-tree callers time to update.
- */
 #define flush_workqueue(wq)						\
 ({									\
 	struct workqueue_struct *_wq = (wq);				\
@@ -714,5 +724,6 @@ int workqueue_offline_cpu(unsigned int cpu);
 
 void __init workqueue_init_early(void);
 void __init workqueue_init(void);
+void __init workqueue_init_topology(void);
 
 #endif

init/main.c

@@ -1540,6 +1540,7 @@ static noinline void __init kernel_init_freeable(void)
 	smp_init();
 	sched_init_smp();
 
+	workqueue_init_topology();
 	padata_init();
 	page_alloc_init_late();
 

kernel/workqueue.c

@@ -122,11 +122,6 @@ enum {
  *
  * L: pool->lock protected.  Access with pool->lock held.
  *
- * X: During normal operation, modification requires pool->lock and should
- *    be done only from local cpu.  Either disabling preemption on local
- *    cpu or grabbing pool->lock is enough for read access.  If
- *    POOL_DISASSOCIATED is set, it's identical to L.
- *
  * K: Only modified by worker while holding pool->lock. Can be safely read by
  *    self, while holding pool->lock or from IRQ context if %current is the
  *    kworker.
@@ -160,7 +155,7 @@ struct worker_pool {
 	int			cpu;		/* I: the associated cpu */
 	int			node;		/* I: the associated node ID */
 	int			id;		/* I: pool ID */
-	unsigned int		flags;		/* X: flags */
+	unsigned int		flags;		/* L: flags */
 
 	unsigned long		watchdog_ts;	/* L: watchdog timestamp */
 	bool			cpu_stall;	/* WD: stalled cpu bound pool */
@@ -216,6 +211,7 @@ enum pool_workqueue_stats {
 	PWQ_STAT_CPU_TIME,	/* total CPU time consumed */
 	PWQ_STAT_CPU_INTENSIVE,	/* wq_cpu_intensive_thresh_us violations */
 	PWQ_STAT_CM_WAKEUP,	/* concurrency-management worker wakeups */
+	PWQ_STAT_REPATRIATED,	/* unbound workers brought back into scope */
 	PWQ_STAT_MAYDAY,	/* maydays to rescuer */
 	PWQ_STAT_RESCUED,	/* linked work items executed by rescuer */
 
@@ -262,12 +258,12 @@ struct pool_workqueue {
 	u64			stats[PWQ_NR_STATS];
 
 	/*
-	 * Release of unbound pwq is punted to system_wq.  See put_pwq()
-	 * and pwq_unbound_release_workfn() for details.  pool_workqueue
-	 * itself is also RCU protected so that the first pwq can be
-	 * determined without grabbing wq->mutex.
+	 * Release of unbound pwq is punted to a kthread_worker. See put_pwq()
+	 * and pwq_release_workfn() for details. pool_workqueue itself is also
+	 * RCU protected so that the first pwq can be determined without
+	 * grabbing wq->mutex.
 	 */
-	struct work_struct	unbound_release_work;
+	struct kthread_work	release_work;
 	struct rcu_head		rcu;
 } __aligned(1 << WORK_STRUCT_FLAG_BITS);
 
@@ -326,14 +322,33 @@ struct workqueue_struct {
 
 	/* hot fields used during command issue, aligned to cacheline */
 	unsigned int		flags ____cacheline_aligned; /* WQ: WQ_* flags */
-	struct pool_workqueue __percpu *cpu_pwqs; /* I: per-cpu pwqs */
-	struct pool_workqueue __rcu *numa_pwq_tbl[]; /* PWR: unbound pwqs indexed by node */
+	struct pool_workqueue __percpu __rcu **cpu_pwq; /* I: per-cpu pwqs */
 };
 
 static struct kmem_cache *pwq_cache;
 
-static cpumask_var_t *wq_numa_possible_cpumask;
-					/* possible CPUs of each node */
+/*
+ * Each pod type describes how CPUs should be grouped for unbound workqueues.
+ * See the comment above workqueue_attrs->affn_scope.
+ */
+struct wq_pod_type {
+	int			nr_pods;	/* number of pods */
+	cpumask_var_t		*pod_cpus;	/* pod -> cpus */
+	int			*pod_node;	/* pod -> node */
+	int			*cpu_pod;	/* cpu -> pod */
+};
+
+static struct wq_pod_type wq_pod_types[WQ_AFFN_NR_TYPES];
+static enum wq_affn_scope wq_affn_dfl = WQ_AFFN_CACHE;
+
+static const char *wq_affn_names[WQ_AFFN_NR_TYPES] = {
+	[WQ_AFFN_DFL]			= "default",
+	[WQ_AFFN_CPU]			= "cpu",
+	[WQ_AFFN_SMT]			= "smt",
+	[WQ_AFFN_CACHE]			= "cache",
+	[WQ_AFFN_NUMA]			= "numa",
+	[WQ_AFFN_SYSTEM]		= "system",
+};
 
 /*
  * Per-cpu work items which run for longer than the following threshold are
@@ -345,19 +360,14 @@ static cpumask_var_t *wq_numa_possible_cpumask;
 static unsigned long wq_cpu_intensive_thresh_us = ULONG_MAX;
 module_param_named(cpu_intensive_thresh_us, wq_cpu_intensive_thresh_us, ulong, 0644);
 
-static bool wq_disable_numa;
-module_param_named(disable_numa, wq_disable_numa, bool, 0444);
-
 /* see the comment above the definition of WQ_POWER_EFFICIENT */
 static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT);
 module_param_named(power_efficient, wq_power_efficient, bool, 0444);
 
 static bool wq_online;			/* can kworkers be created yet? */
 
-static bool wq_numa_enabled;		/* unbound NUMA affinity enabled */
-
-/* buf for wq_update_unbound_numa_attrs(), protected by CPU hotplug exclusion */
-static struct workqueue_attrs *wq_update_unbound_numa_attrs_buf;
+/* buf for wq_update_unbound_pod_attrs(), protected by CPU hotplug exclusion */
+static struct workqueue_attrs *wq_update_pod_attrs_buf;
 
 static DEFINE_MUTEX(wq_pool_mutex);	/* protects pools and workqueues list */
 static DEFINE_MUTEX(wq_pool_attach_mutex); /* protects worker attach/detach */
@@ -371,6 +381,9 @@ static bool workqueue_freezing;		/* PL: have wqs started freezing? */
 /* PL&A: allowable cpus for unbound wqs and work items */
 static cpumask_var_t wq_unbound_cpumask;
 
+/* for further constrain wq_unbound_cpumask by cmdline parameter*/
+static struct cpumask wq_cmdline_cpumask __initdata;
+
 /* CPU where unbound work was last round robin scheduled from this CPU */
 static DEFINE_PER_CPU(int, wq_rr_cpu_last);
 
@@ -400,6 +413,13 @@ static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS];
 /* I: attributes used when instantiating ordered pools on demand */
 static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS];
 
+/*
+ * I: kthread_worker to release pwq's. pwq release needs to be bounced to a
+ * process context while holding a pool lock. Bounce to a dedicated kthread
+ * worker to avoid A-A deadlocks.
+ */
+static struct kthread_worker *pwq_release_worker;
+
 struct workqueue_struct *system_wq __read_mostly;
 EXPORT_SYMBOL(system_wq);
 struct workqueue_struct *system_highpri_wq __read_mostly;
@@ -606,35 +626,6 @@ static int worker_pool_assign_id(struct worker_pool *pool)
 	return ret;
 }
 
-/**
- * unbound_pwq_by_node - return the unbound pool_workqueue for the given node
- * @wq: the target workqueue
- * @node: the node ID
- *
- * This must be called with any of wq_pool_mutex, wq->mutex or RCU
- * read locked.
- * If the pwq needs to be used beyond the locking in effect, the caller is
- * responsible for guaranteeing that the pwq stays online.
- *
- * Return: The unbound pool_workqueue for @node.
- */
-static struct pool_workqueue *unbound_pwq_by_node(struct workqueue_struct *wq,
-						  int node)
-{
-	assert_rcu_or_wq_mutex_or_pool_mutex(wq);
-
-	/*
-	 * XXX: @node can be NUMA_NO_NODE if CPU goes offline while a
-	 * delayed item is pending.  The plan is to keep CPU -> NODE
-	 * mapping valid and stable across CPU on/offlines.  Once that
-	 * happens, this workaround can be removed.
-	 */
-	if (unlikely(node == NUMA_NO_NODE))
-		return wq->dfl_pwq;
-
-	return rcu_dereference_raw(wq->numa_pwq_tbl[node]);
-}
-
 static unsigned int work_color_to_flags(int color)
 {
 	return color << WORK_STRUCT_COLOR_SHIFT;
@@ -825,11 +816,6 @@ static bool work_is_canceling(struct work_struct *work)
  * they're being called with pool->lock held.
  */
 
-static bool __need_more_worker(struct worker_pool *pool)
-{
-	return !pool->nr_running;
-}
-
 /*
  * Need to wake up a worker?  Called from anything but currently
  * running workers.
@@ -840,7 +826,7 @@ static bool __need_more_worker(struct worker_pool *pool)
  */
 static bool need_more_worker(struct worker_pool *pool)
 {
-	return !list_empty(&pool->worklist) && __need_more_worker(pool);
+	return !list_empty(&pool->worklist) && !pool->nr_running;
 }
 
 /* Can I start working?  Called from busy but !running workers. */
@@ -871,51 +857,18 @@ static bool too_many_workers(struct worker_pool *pool)
 	return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
 }
 
-/*
- * Wake up functions.
- */
-
-/* Return the first idle worker.  Called with pool->lock held. */
-static struct worker *first_idle_worker(struct worker_pool *pool)
-{
-	if (unlikely(list_empty(&pool->idle_list)))
-		return NULL;
-
-	return list_first_entry(&pool->idle_list, struct worker, entry);
-}
-
-/**
- * wake_up_worker - wake up an idle worker
- * @pool: worker pool to wake worker from
- *
- * Wake up the first idle worker of @pool.
- *
- * CONTEXT:
- * raw_spin_lock_irq(pool->lock).
- */
-static void wake_up_worker(struct worker_pool *pool)
-{
-	struct worker *worker = first_idle_worker(pool);
-
-	if (likely(worker))
-		wake_up_process(worker->task);
-}
-
 /**
  * worker_set_flags - set worker flags and adjust nr_running accordingly
  * @worker: self
  * @flags: flags to set
  *
  * Set @flags in @worker->flags and adjust nr_running accordingly.
- *
- * CONTEXT:
- * raw_spin_lock_irq(pool->lock)
  */
 static inline void worker_set_flags(struct worker *worker, unsigned int flags)
 {
 	struct worker_pool *pool = worker->pool;
 
-	WARN_ON_ONCE(worker->task != current);
+	lockdep_assert_held(&pool->lock);
 
 	/* If transitioning into NOT_RUNNING, adjust nr_running. */
 	if ((flags & WORKER_NOT_RUNNING) &&
@@ -932,16 +885,13 @@ static inline void worker_set_flags(struct worker *worker, unsigned int flags)
  * @flags: flags to clear
  *
  * Clear @flags in @worker->flags and adjust nr_running accordingly.
- *
- * CONTEXT:
- * raw_spin_lock_irq(pool->lock)
  */
 static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
 {
 	struct worker_pool *pool = worker->pool;
 	unsigned int oflags = worker->flags;
 
-	WARN_ON_ONCE(worker->task != current);
+	lockdep_assert_held(&pool->lock);
 
 	worker->flags &= ~flags;
 
@@ -955,6 +905,244 @@ static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
 			pool->nr_running++;
 }
 
+/* Return the first idle worker.  Called with pool->lock held. */
+static struct worker *first_idle_worker(struct worker_pool *pool)
+{
+	if (unlikely(list_empty(&pool->idle_list)))
+		return NULL;
+
+	return list_first_entry(&pool->idle_list, struct worker, entry);
+}
+
+/**
+ * worker_enter_idle - enter idle state
+ * @worker: worker which is entering idle state
+ *
+ * @worker is entering idle state.  Update stats and idle timer if
+ * necessary.
+ *
+ * LOCKING:
+ * raw_spin_lock_irq(pool->lock).
+ */
+static void worker_enter_idle(struct worker *worker)
+{
+	struct worker_pool *pool = worker->pool;
+
+	if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) ||
+	    WARN_ON_ONCE(!list_empty(&worker->entry) &&
+			 (worker->hentry.next || worker->hentry.pprev)))
+		return;
+
+	/* can't use worker_set_flags(), also called from create_worker() */
+	worker->flags |= WORKER_IDLE;
+	pool->nr_idle++;
+	worker->last_active = jiffies;
+
+	/* idle_list is LIFO */
+	list_add(&worker->entry, &pool->idle_list);
+
+	if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
+		mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
+
+	/* Sanity check nr_running. */
+	WARN_ON_ONCE(pool->nr_workers == pool->nr_idle && pool->nr_running);
+}
+
+/**
+ * worker_leave_idle - leave idle state
+ * @worker: worker which is leaving idle state
+ *
+ * @worker is leaving idle state.  Update stats.
+ *
+ * LOCKING:
+ * raw_spin_lock_irq(pool->lock).
+ */
+static void worker_leave_idle(struct worker *worker)
+{
+	struct worker_pool *pool = worker->pool;
+
+	if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE)))
+		return;
+	worker_clr_flags(worker, WORKER_IDLE);
+	pool->nr_idle--;
+	list_del_init(&worker->entry);
+}
+
+/**
+ * find_worker_executing_work - find worker which is executing a work
+ * @pool: pool of interest
+ * @work: work to find worker for
+ *
+ * Find a worker which is executing @work on @pool by searching
+ * @pool->busy_hash which is keyed by the address of @work.  For a worker
+ * to match, its current execution should match the address of @work and
+ * its work function.  This is to avoid unwanted dependency between
+ * unrelated work executions through a work item being recycled while still
+ * being executed.
+ *
+ * This is a bit tricky.  A work item may be freed once its execution
+ * starts and nothing prevents the freed area from being recycled for
+ * another work item.  If the same work item address ends up being reused
+ * before the original execution finishes, workqueue will identify the
+ * recycled work item as currently executing and make it wait until the
+ * current execution finishes, introducing an unwanted dependency.
+ *
+ * This function checks the work item address and work function to avoid
+ * false positives.  Note that this isn't complete as one may construct a
+ * work function which can introduce dependency onto itself through a
+ * recycled work item.  Well, if somebody wants to shoot oneself in the
+ * foot that badly, there's only so much we can do, and if such deadlock
+ * actually occurs, it should be easy to locate the culprit work function.
+ *
+ * CONTEXT:
+ * raw_spin_lock_irq(pool->lock).
+ *
+ * Return:
+ * Pointer to worker which is executing @work if found, %NULL
+ * otherwise.
+ */
+static struct worker *find_worker_executing_work(struct worker_pool *pool,
+						 struct work_struct *work)
+{
+	struct worker *worker;
+
+	hash_for_each_possible(pool->busy_hash, worker, hentry,
+			       (unsigned long)work)
+		if (worker->current_work == work &&
+		    worker->current_func == work->func)
+			return worker;
+
+	return NULL;
+}
+
+/**
+ * move_linked_works - move linked works to a list
+ * @work: start of series of works to be scheduled
+ * @head: target list to append @work to
+ * @nextp: out parameter for nested worklist walking
+ *
+ * Schedule linked works starting from @work to @head. Work series to be
+ * scheduled starts at @work and includes any consecutive work with
+ * WORK_STRUCT_LINKED set in its predecessor. See assign_work() for details on
+ * @nextp.
+ *
+ * CONTEXT:
+ * raw_spin_lock_irq(pool->lock).
+ */
+static void move_linked_works(struct work_struct *work, struct list_head *head,
+			      struct work_struct **nextp)
+{
+	struct work_struct *n;
+
+	/*
+	 * Linked worklist will always end before the end of the list,
+	 * use NULL for list head.
+	 */
+	list_for_each_entry_safe_from(work, n, NULL, entry) {
+		list_move_tail(&work->entry, head);
+		if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
+			break;
+	}
+
+	/*
+	 * If we're already inside safe list traversal and have moved
+	 * multiple works to the scheduled queue, the next position
+	 * needs to be updated.
+	 */
+	if (nextp)
+		*nextp = n;
+}
+
+/**
+ * assign_work - assign a work item and its linked work items to a worker
+ * @work: work to assign
+ * @worker: worker to assign to
+ * @nextp: out parameter for nested worklist walking
+ *
+ * Assign @work and its linked work items to @worker. If @work is already being
+ * executed by another worker in the same pool, it'll be punted there.
+ *
+ * If @nextp is not NULL, it's updated to point to the next work of the last
+ * scheduled work. This allows assign_work() to be nested inside
+ * list_for_each_entry_safe().
+ *
+ * Returns %true if @work was successfully assigned to @worker. %false if @work
+ * was punted to another worker already executing it.
+ */
+static bool assign_work(struct work_struct *work, struct worker *worker,
+			struct work_struct **nextp)
+{
+	struct worker_pool *pool = worker->pool;
+	struct worker *collision;
+
+	lockdep_assert_held(&pool->lock);
+
+	/*
+	 * A single work shouldn't be executed concurrently by multiple workers.
+	 * __queue_work() ensures that @work doesn't jump to a different pool
+	 * while still running in the previous pool. Here, we should ensure that
+	 * @work is not executed concurrently by multiple workers from the same
+	 * pool. Check whether anyone is already processing the work. If so,
+	 * defer the work to the currently executing one.
+	 */
+	collision = find_worker_executing_work(pool, work);
+	if (unlikely(collision)) {
+		move_linked_works(work, &collision->scheduled, nextp);
+		return false;
+	}
+
+	move_linked_works(work, &worker->scheduled, nextp);
+	return true;
+}
+
+/**
+ * kick_pool - wake up an idle worker if necessary
+ * @pool: pool to kick
+ *
+ * @pool may have pending work items. Wake up worker if necessary. Returns
+ * whether a worker was woken up.
+ */
+static bool kick_pool(struct worker_pool *pool)
+{
+	struct worker *worker = first_idle_worker(pool);
+	struct task_struct *p;
+
+	lockdep_assert_held(&pool->lock);
+
+	if (!need_more_worker(pool) || !worker)
+		return false;
+
+	p = worker->task;
+
+#ifdef CONFIG_SMP
+	/*
+	 * Idle @worker is about to execute @work and waking up provides an
+	 * opportunity to migrate @worker at a lower cost by setting the task's
+	 * wake_cpu field. Let's see if we want to move @worker to improve
+	 * execution locality.
+	 *
+	 * We're waking the worker that went idle the latest and there's some
+	 * chance that @worker is marked idle but hasn't gone off CPU yet. If
+	 * so, setting the wake_cpu won't do anything. As this is a best-effort
+	 * optimization and the race window is narrow, let's leave as-is for
+	 * now. If this becomes pronounced, we can skip over workers which are
+	 * still on cpu when picking an idle worker.
+	 *
+	 * If @pool has non-strict affinity, @worker might have ended up outside
+	 * its affinity scope. Repatriate.
+	 */
+	if (!pool->attrs->affn_strict &&
+	    !cpumask_test_cpu(p->wake_cpu, pool->attrs->__pod_cpumask)) {
+		struct work_struct *work = list_first_entry(&pool->worklist,
+						struct work_struct, entry);
+		p->wake_cpu = cpumask_any_distribute(pool->attrs->__pod_cpumask);
+		get_work_pwq(work)->stats[PWQ_STAT_REPATRIATED]++;
+	}
+#endif
+	wake_up_process(p);
+	return true;
+}
+
 #ifdef CONFIG_WQ_CPU_INTENSIVE_REPORT
 
 /*
@@ -1120,10 +1308,9 @@ void wq_worker_sleeping(struct task_struct *task)
 	}
 
 	pool->nr_running--;
-	if (need_more_worker(pool)) {
+	if (kick_pool(pool))
 		worker->current_pwq->stats[PWQ_STAT_CM_WAKEUP]++;
-		wake_up_worker(pool);
-	}
+
 	raw_spin_unlock_irq(&pool->lock);
 }
 
@@ -1171,10 +1358,8 @@ void wq_worker_tick(struct task_struct *task)
 	wq_cpu_intensive_report(worker->current_func);
 	pwq->stats[PWQ_STAT_CPU_INTENSIVE]++;
 
-	if (need_more_worker(pool)) {
+	if (kick_pool(pool))
 		pwq->stats[PWQ_STAT_CM_WAKEUP]++;
-		wake_up_worker(pool);
-	}
 
 	raw_spin_unlock(&pool->lock);
 }
@@ -1210,94 +1395,6 @@ work_func_t wq_worker_last_func(struct task_struct *task)
 	return worker->last_func;
 }
 
-/**
- * find_worker_executing_work - find worker which is executing a work
- * @pool: pool of interest
- * @work: work to find worker for
- *
- * Find a worker which is executing @work on @pool by searching
- * @pool->busy_hash which is keyed by the address of @work.  For a worker
- * to match, its current execution should match the address of @work and
- * its work function.  This is to avoid unwanted dependency between
- * unrelated work executions through a work item being recycled while still
- * being executed.
- *
- * This is a bit tricky.  A work item may be freed once its execution
- * starts and nothing prevents the freed area from being recycled for
- * another work item.  If the same work item address ends up being reused
- * before the original execution finishes, workqueue will identify the
- * recycled work item as currently executing and make it wait until the
- * current execution finishes, introducing an unwanted dependency.
- *
- * This function checks the work item address and work function to avoid
- * false positives.  Note that this isn't complete as one may construct a
- * work function which can introduce dependency onto itself through a
- * recycled work item.  Well, if somebody wants to shoot oneself in the
- * foot that badly, there's only so much we can do, and if such deadlock
- * actually occurs, it should be easy to locate the culprit work function.
- *
- * CONTEXT:
- * raw_spin_lock_irq(pool->lock).
- *
- * Return:
- * Pointer to worker which is executing @work if found, %NULL
- * otherwise.
- */
-static struct worker *find_worker_executing_work(struct worker_pool *pool,
-						 struct work_struct *work)
-{
-	struct worker *worker;
-
-	hash_for_each_possible(pool->busy_hash, worker, hentry,
-			       (unsigned long)work)
-		if (worker->current_work == work &&
-		    worker->current_func == work->func)
-			return worker;
-
-	return NULL;
-}
-
-/**
- * move_linked_works - move linked works to a list
- * @work: start of series of works to be scheduled
- * @head: target list to append @work to
- * @nextp: out parameter for nested worklist walking
- *
- * Schedule linked works starting from @work to @head.  Work series to
- * be scheduled starts at @work and includes any consecutive work with
- * WORK_STRUCT_LINKED set in its predecessor.
- *
- * If @nextp is not NULL, it's updated to point to the next work of
- * the last scheduled work.  This allows move_linked_works() to be
- * nested inside outer list_for_each_entry_safe().
- *
- * CONTEXT:
- * raw_spin_lock_irq(pool->lock).
- */
-static void move_linked_works(struct work_struct *work, struct list_head *head,
-			      struct work_struct **nextp)
-{
-	struct work_struct *n;
-
-	/*
-	 * Linked worklist will always end before the end of the list,
-	 * use NULL for list head.
-	 */
-	list_for_each_entry_safe_from(work, n, NULL, entry) {
-		list_move_tail(&work->entry, head);
-		if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
-			break;
-	}
-
-	/*
-	 * If we're already inside safe list traversal and have moved
-	 * multiple works to the scheduled queue, the next position
-	 * needs to be updated.
-	 */
-	if (nextp)
-		*nextp = n;
-}
-
 /**
  * get_pwq - get an extra reference on the specified pool_workqueue
  * @pwq: pool_workqueue to get
@@ -1324,17 +1421,11 @@ static void put_pwq(struct pool_workqueue *pwq)
 	lockdep_assert_held(&pwq->pool->lock);
 	if (likely(--pwq->refcnt))
 		return;
-	if (WARN_ON_ONCE(!(pwq->wq->flags & WQ_UNBOUND)))
-		return;
 	/*
-	 * @pwq can't be released under pool->lock, bounce to
-	 * pwq_unbound_release_workfn().  This never recurses on the same
-	 * pool->lock as this path is taken only for unbound workqueues and
-	 * the release work item is scheduled on a per-cpu workqueue.  To
-	 * avoid lockdep warning, unbound pool->locks are given lockdep
-	 * subclass of 1 in get_unbound_pool().
+	 * @pwq can't be released under pool->lock, bounce to a dedicated
+	 * kthread_worker to avoid A-A deadlocks.
 	 */
-	schedule_work(&pwq->unbound_release_work);
+	kthread_queue_work(pwq_release_worker, &pwq->release_work);
 }
 
 /**
@@ -1550,7 +1641,7 @@ static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
 static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
 			struct list_head *head, unsigned int extra_flags)
 {
-	struct worker_pool *pool = pwq->pool;
+	debug_work_activate(work);
 
 	/* record the work call stack in order to print it in KASAN reports */
 	kasan_record_aux_stack_noalloc(work);
@@ -1559,9 +1650,6 @@ static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
 	set_work_pwq(work, pwq, extra_flags);
 	list_add_tail(&work->entry, head);
 	get_pwq(pwq);
-
-	if (__need_more_worker(pool))
-		wake_up_worker(pool);
 }
 
 /*
@@ -1615,8 +1703,7 @@ static void __queue_work(int cpu, struct workqueue_struct *wq,
 			 struct work_struct *work)
 {
 	struct pool_workqueue *pwq;
-	struct worker_pool *last_pool;
-	struct list_head *worklist;
+	struct worker_pool *last_pool, *pool;
 	unsigned int work_flags;
 	unsigned int req_cpu = cpu;
 
@@ -1640,23 +1727,23 @@ static void __queue_work(int cpu, struct workqueue_struct *wq,
 	rcu_read_lock();
 retry:
 	/* pwq which will be used unless @work is executing elsewhere */
-	if (wq->flags & WQ_UNBOUND) {
-		if (req_cpu == WORK_CPU_UNBOUND)
+	if (req_cpu == WORK_CPU_UNBOUND) {
+		if (wq->flags & WQ_UNBOUND)
 			cpu = wq_select_unbound_cpu(raw_smp_processor_id());
-		pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
-	} else {
-		if (req_cpu == WORK_CPU_UNBOUND)
+		else
 			cpu = raw_smp_processor_id();
-		pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
 	}
 
+	pwq = rcu_dereference(*per_cpu_ptr(wq->cpu_pwq, cpu));
+	pool = pwq->pool;
+
 	/*
 	 * If @work was previously on a different pool, it might still be
 	 * running there, in which case the work needs to be queued on that
 	 * pool to guarantee non-reentrancy.
 	 */
 	last_pool = get_work_pool(work);
-	if (last_pool && last_pool != pwq->pool) {
+	if (last_pool && last_pool != pool) {
 		struct worker *worker;
 
 		raw_spin_lock(&last_pool->lock);
@@ -1665,26 +1752,27 @@ static void __queue_work(int cpu, struct workqueue_struct *wq,
 
 		if (worker && worker->current_pwq->wq == wq) {
 			pwq = worker->current_pwq;
+			pool = pwq->pool;
+			WARN_ON_ONCE(pool != last_pool);
 		} else {
 			/* meh... not running there, queue here */
 			raw_spin_unlock(&last_pool->lock);
-			raw_spin_lock(&pwq->pool->lock);
+			raw_spin_lock(&pool->lock);
 		}
 	} else {
-		raw_spin_lock(&pwq->pool->lock);
+		raw_spin_lock(&pool->lock);
 	}
 
 	/*
-	 * pwq is determined and locked.  For unbound pools, we could have
-	 * raced with pwq release and it could already be dead.  If its
-	 * refcnt is zero, repeat pwq selection.  Note that pwqs never die
-	 * without another pwq replacing it in the numa_pwq_tbl or while
-	 * work items are executing on it, so the retrying is guaranteed to
-	 * make forward-progress.
+	 * pwq is determined and locked. For unbound pools, we could have raced
+	 * with pwq release and it could already be dead. If its refcnt is zero,
+	 * repeat pwq selection. Note that unbound pwqs never die without
+	 * another pwq replacing it in cpu_pwq or while work items are executing
+	 * on it, so the retrying is guaranteed to make forward-progress.
 	 */
 	if (unlikely(!pwq->refcnt)) {
 		if (wq->flags & WQ_UNBOUND) {
-			raw_spin_unlock(&pwq->pool->lock);
+			raw_spin_unlock(&pool->lock);
 			cpu_relax();
 			goto retry;
 		}
@@ -1703,21 +1791,20 @@ static void __queue_work(int cpu, struct workqueue_struct *wq,
 	work_flags = work_color_to_flags(pwq->work_color);
 
 	if (likely(pwq->nr_active < pwq->max_active)) {
+		if (list_empty(&pool->worklist))
+			pool->watchdog_ts = jiffies;
+
 		trace_workqueue_activate_work(work);
 		pwq->nr_active++;
-		worklist = &pwq->pool->worklist;
-		if (list_empty(worklist))
-			pwq->pool->watchdog_ts = jiffies;
+		insert_work(pwq, work, &pool->worklist, work_flags);
+		kick_pool(pool);
 	} else {
 		work_flags |= WORK_STRUCT_INACTIVE;
-		worklist = &pwq->inactive_works;
+		insert_work(pwq, work, &pwq->inactive_works, work_flags);
 	}
 
-	debug_work_activate(work);
-	insert_work(pwq, work, worklist, work_flags);
-
 out:
-	raw_spin_unlock(&pwq->pool->lock);
+	raw_spin_unlock(&pool->lock);
 	rcu_read_unlock();
 }
 
@@ -1754,7 +1841,7 @@ bool queue_work_on(int cpu, struct workqueue_struct *wq,
 EXPORT_SYMBOL(queue_work_on);
 
 /**
- * workqueue_select_cpu_near - Select a CPU based on NUMA node
+ * select_numa_node_cpu - Select a CPU based on NUMA node
  * @node: NUMA node ID that we want to select a CPU from
  *
  * This function will attempt to find a "random" cpu available on a given
@@ -1762,14 +1849,10 @@ EXPORT_SYMBOL(queue_work_on);
  * WORK_CPU_UNBOUND indicating that we should just schedule to any
  * available CPU if we need to schedule this work.
  */
-static int workqueue_select_cpu_near(int node)
+static int select_numa_node_cpu(int node)
 {
 	int cpu;
 
-	/* No point in doing this if NUMA isn't enabled for workqueues */
-	if (!wq_numa_enabled)
-		return WORK_CPU_UNBOUND;
-
 	/* Delay binding to CPU if node is not valid or online */
 	if (node < 0 || node >= MAX_NUMNODES || !node_online(node))
 		return WORK_CPU_UNBOUND;
@@ -1826,7 +1909,7 @@ bool queue_work_node(int node, struct workqueue_struct *wq,
 	local_irq_save(flags);
 
 	if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
-		int cpu = workqueue_select_cpu_near(node);
+		int cpu = select_numa_node_cpu(node);
 
 		__queue_work(cpu, wq, work);
 		ret = true;
@@ -1981,60 +2064,6 @@ bool queue_rcu_work(struct workqueue_struct *wq, struct rcu_work *rwork)
 }
 EXPORT_SYMBOL(queue_rcu_work);
 
-/**
- * worker_enter_idle - enter idle state
- * @worker: worker which is entering idle state
- *
- * @worker is entering idle state.  Update stats and idle timer if
- * necessary.
- *
- * LOCKING:
- * raw_spin_lock_irq(pool->lock).
- */
-static void worker_enter_idle(struct worker *worker)
-{
-	struct worker_pool *pool = worker->pool;
-
-	if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) ||
-	    WARN_ON_ONCE(!list_empty(&worker->entry) &&
-			 (worker->hentry.next || worker->hentry.pprev)))
-		return;
-
-	/* can't use worker_set_flags(), also called from create_worker() */
-	worker->flags |= WORKER_IDLE;
-	pool->nr_idle++;
-	worker->last_active = jiffies;
-
-	/* idle_list is LIFO */
-	list_add(&worker->entry, &pool->idle_list);
-
-	if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
-		mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
-
-	/* Sanity check nr_running. */
-	WARN_ON_ONCE(pool->nr_workers == pool->nr_idle && pool->nr_running);
-}
-
-/**
- * worker_leave_idle - leave idle state
- * @worker: worker which is leaving idle state
- *
- * @worker is leaving idle state.  Update stats.
- *
- * LOCKING:
- * raw_spin_lock_irq(pool->lock).
- */
-static void worker_leave_idle(struct worker *worker)
-{
-	struct worker_pool *pool = worker->pool;
-
-	if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE)))
-		return;
-	worker_clr_flags(worker, WORKER_IDLE);
-	pool->nr_idle--;
-	list_del_init(&worker->entry);
-}
-
 static struct worker *alloc_worker(int node)
 {
 	struct worker *worker;
@@ -2050,6 +2079,14 @@ static struct worker *alloc_worker(int node)
 	return worker;
 }
 
+static cpumask_t *pool_allowed_cpus(struct worker_pool *pool)
+{
+	if (pool->cpu < 0 && pool->attrs->affn_strict)
+		return pool->attrs->__pod_cpumask;
+	else
+		return pool->attrs->cpumask;
+}
+
 /**
  * worker_attach_to_pool() - attach a worker to a pool
  * @worker: worker to be attached
@@ -2075,7 +2112,7 @@ static void worker_attach_to_pool(struct worker *worker,
 		kthread_set_per_cpu(worker->task, pool->cpu);
 
 	if (worker->rescue_wq)
-		set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask);
+		set_cpus_allowed_ptr(worker->task, pool_allowed_cpus(pool));
 
 	list_add_tail(&worker->node, &pool->workers);
 	worker->pool = pool;
@@ -2167,16 +2204,25 @@ static struct worker *create_worker(struct worker_pool *pool)
 	}
 
 	set_user_nice(worker->task, pool->attrs->nice);
-	kthread_bind_mask(worker->task, pool->attrs->cpumask);
+	kthread_bind_mask(worker->task, pool_allowed_cpus(pool));
 
 	/* successful, attach the worker to the pool */
 	worker_attach_to_pool(worker, pool);
 
 	/* start the newly created worker */
 	raw_spin_lock_irq(&pool->lock);
+
 	worker->pool->nr_workers++;
 	worker_enter_idle(worker);
+	kick_pool(pool);
+
+	/*
+	 * @worker is waiting on a completion in kthread() and will trigger hung
+	 * check if not woken up soon. As kick_pool() might not have waken it
+	 * up, wake it up explicitly once more.
+	 */
 	wake_up_process(worker->task);
+
 	raw_spin_unlock_irq(&pool->lock);
 
 	return worker;
@@ -2304,9 +2350,8 @@ static void idle_worker_timeout(struct timer_list *t)
 static void idle_cull_fn(struct work_struct *work)
 {
 	struct worker_pool *pool = container_of(work, struct worker_pool, idle_cull_work);
-	struct list_head cull_list;
+	LIST_HEAD(cull_list);
 
-	INIT_LIST_HEAD(&cull_list);
 	/*
 	 * Grabbing wq_pool_attach_mutex here ensures an already-running worker
 	 * cannot proceed beyong worker_detach_from_pool() in its self-destruct
@@ -2495,7 +2540,6 @@ __acquires(&pool->lock)
 	struct pool_workqueue *pwq = get_work_pwq(work);
 	struct worker_pool *pool = worker->pool;
 	unsigned long work_data;
-	struct worker *collision;
 #ifdef CONFIG_LOCKDEP
 	/*
 	 * It is permissible to free the struct work_struct from
@@ -2512,18 +2556,6 @@ __acquires(&pool->lock)
 	WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
 		     raw_smp_processor_id() != pool->cpu);
 
-	/*
-	 * A single work shouldn't be executed concurrently by
-	 * multiple workers on a single cpu.  Check whether anyone is
-	 * already processing the work.  If so, defer the work to the
-	 * currently executing one.
-	 */
-	collision = find_worker_executing_work(pool, work);
-	if (unlikely(collision)) {
-		move_linked_works(work, &collision->scheduled, NULL);
-		return;
-	}
-
 	/* claim and dequeue */
 	debug_work_deactivate(work);
 	hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work);
@@ -2552,14 +2584,12 @@ __acquires(&pool->lock)
 		worker_set_flags(worker, WORKER_CPU_INTENSIVE);
 
 	/*
-	 * Wake up another worker if necessary.  The condition is always
-	 * false for normal per-cpu workers since nr_running would always
-	 * be >= 1 at this point.  This is used to chain execution of the
-	 * pending work items for WORKER_NOT_RUNNING workers such as the
-	 * UNBOUND and CPU_INTENSIVE ones.
+	 * Kick @pool if necessary. It's always noop for per-cpu worker pools
+	 * since nr_running would always be >= 1 at this point. This is used to
+	 * chain execution of the pending work items for WORKER_NOT_RUNNING
+	 * workers such as the UNBOUND and CPU_INTENSIVE ones.
 	 */
-	if (need_more_worker(pool))
-		wake_up_worker(pool);
+	kick_pool(pool);
 
 	/*
 	 * Record the last pool and clear PENDING which should be the last
@@ -2569,6 +2599,7 @@ __acquires(&pool->lock)
 	 */
 	set_work_pool_and_clear_pending(work, pool->id);
 
+	pwq->stats[PWQ_STAT_STARTED]++;
 	raw_spin_unlock_irq(&pool->lock);
 
 	lock_map_acquire(&pwq->wq->lockdep_map);
@@ -2595,7 +2626,6 @@ __acquires(&pool->lock)
 	 * workqueues), so hiding them isn't a problem.
 	 */
 	lockdep_invariant_state(true);
-	pwq->stats[PWQ_STAT_STARTED]++;
 	trace_workqueue_execute_start(work);
 	worker->current_func(work);
 	/*
@@ -2661,9 +2691,15 @@ __acquires(&pool->lock)
  */
 static void process_scheduled_works(struct worker *worker)
 {
-	while (!list_empty(&worker->scheduled)) {
-		struct work_struct *work = list_first_entry(&worker->scheduled,
-						struct work_struct, entry);
+	struct work_struct *work;
+	bool first = true;
+
+	while ((work = list_first_entry_or_null(&worker->scheduled,
+						struct work_struct, entry))) {
+		if (first) {
+			worker->pool->watchdog_ts = jiffies;
+			first = false;
+		}
 		process_one_work(worker, work);
 	}
 }
@@ -2744,17 +2780,8 @@ static int worker_thread(void *__worker)
 			list_first_entry(&pool->worklist,
 					 struct work_struct, entry);
 
-		pool->watchdog_ts = jiffies;
-
-		if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
-			/* optimization path, not strictly necessary */
-			process_one_work(worker, work);
-			if (unlikely(!list_empty(&worker->scheduled)))
-				process_scheduled_works(worker);
-		} else {
-			move_linked_works(work, &worker->scheduled, NULL);
+		if (assign_work(work, worker, NULL))
 			process_scheduled_works(worker);
-		}
 	} while (keep_working(pool));
 
 	worker_set_flags(worker, WORKER_PREP);
@@ -2798,7 +2825,6 @@ static int rescuer_thread(void *__rescuer)
 {
 	struct worker *rescuer = __rescuer;
 	struct workqueue_struct *wq = rescuer->rescue_wq;
-	struct list_head *scheduled = &rescuer->scheduled;
 	bool should_stop;
 
 	set_user_nice(current, RESCUER_NICE_LEVEL);
@@ -2829,7 +2855,6 @@ static int rescuer_thread(void *__rescuer)
 					struct pool_workqueue, mayday_node);
 		struct worker_pool *pool = pwq->pool;
 		struct work_struct *work, *n;
-		bool first = true;
 
 		__set_current_state(TASK_RUNNING);
 		list_del_init(&pwq->mayday_node);
@@ -2844,18 +2869,14 @@ static int rescuer_thread(void *__rescuer)
 		 * Slurp in all works issued via this workqueue and
 		 * process'em.
 		 */
-		WARN_ON_ONCE(!list_empty(scheduled));
+		WARN_ON_ONCE(!list_empty(&rescuer->scheduled));
 		list_for_each_entry_safe(work, n, &pool->worklist, entry) {
-			if (get_work_pwq(work) == pwq) {
-				if (first)
-					pool->watchdog_ts = jiffies;
-				move_linked_works(work, scheduled, &n);
+			if (get_work_pwq(work) == pwq &&
+			    assign_work(work, rescuer, &n))
 				pwq->stats[PWQ_STAT_RESCUED]++;
 		}
-			first = false;
-		}
 
-		if (!list_empty(scheduled)) {
+		if (!list_empty(&rescuer->scheduled)) {
 			process_scheduled_works(rescuer);
 
 			/*
@@ -2888,12 +2909,10 @@ static int rescuer_thread(void *__rescuer)
 		put_pwq(pwq);
 
 		/*
-		 * Leave this pool.  If need_more_worker() is %true, notify a
-		 * regular worker; otherwise, we end up with 0 concurrency
-		 * and stalling the execution.
+		 * Leave this pool. Notify regular workers; otherwise, we end up
+		 * with 0 concurrency and stalling the execution.
 		 */
-		if (need_more_worker(pool))
-			wake_up_worker(pool);
+		kick_pool(pool);
 
 		raw_spin_unlock_irq(&pool->lock);
 
@@ -3028,7 +3047,6 @@ static void insert_wq_barrier(struct pool_workqueue *pwq,
 	pwq->nr_in_flight[work_color]++;
 	work_flags |= work_color_to_flags(work_color);
 
-	debug_work_activate(&barr->work);
 	insert_work(pwq, &barr->work, head, work_flags);
 }
 
@@ -3691,6 +3709,7 @@ void free_workqueue_attrs(struct workqueue_attrs *attrs)
 {
 	if (attrs) {
 		free_cpumask_var(attrs->cpumask);
+		free_cpumask_var(attrs->__pod_cpumask);
 		kfree(attrs);
 	}
 }
@@ -3712,8 +3731,11 @@ struct workqueue_attrs *alloc_workqueue_attrs(void)
 		goto fail;
 	if (!alloc_cpumask_var(&attrs->cpumask, GFP_KERNEL))
 		goto fail;
+	if (!alloc_cpumask_var(&attrs->__pod_cpumask, GFP_KERNEL))
+		goto fail;
 
 	cpumask_copy(attrs->cpumask, cpu_possible_mask);
+	attrs->affn_scope = WQ_AFFN_DFL;
 	return attrs;
 fail:
 	free_workqueue_attrs(attrs);
@@ -3725,12 +3747,26 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to,
 {
 	to->nice = from->nice;
 	cpumask_copy(to->cpumask, from->cpumask);
+	cpumask_copy(to->__pod_cpumask, from->__pod_cpumask);
+	to->affn_strict = from->affn_strict;
+
 	/*
-	 * Unlike hash and equality test, this function doesn't ignore
-	 * ->no_numa as it is used for both pool and wq attrs.  Instead,
-	 * get_unbound_pool() explicitly clears ->no_numa after copying.
+	 * Unlike hash and equality test, copying shouldn't ignore wq-only
+	 * fields as copying is used for both pool and wq attrs. Instead,
+	 * get_unbound_pool() explicitly clears the fields.
+	 */
+	to->affn_scope = from->affn_scope;
+	to->ordered = from->ordered;
+}
+
+/*
+ * Some attrs fields are workqueue-only. Clear them for worker_pool's. See the
+ * comments in 'struct workqueue_attrs' definition.
  */
-	to->no_numa = from->no_numa;
+static void wqattrs_clear_for_pool(struct workqueue_attrs *attrs)
+{
+	attrs->affn_scope = WQ_AFFN_NR_TYPES;
+	attrs->ordered = false;
 }
 
 /* hash value of the content of @attr */
@@ -3741,6 +3777,9 @@ static u32 wqattrs_hash(const struct workqueue_attrs *attrs)
 	hash = jhash_1word(attrs->nice, hash);
 	hash = jhash(cpumask_bits(attrs->cpumask),
 		     BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
+	hash = jhash(cpumask_bits(attrs->__pod_cpumask),
+		     BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
+	hash = jhash_1word(attrs->affn_strict, hash);
 	return hash;
 }
 
@@ -3752,9 +3791,57 @@ static bool wqattrs_equal(const struct workqueue_attrs *a,
 		return false;
 	if (!cpumask_equal(a->cpumask, b->cpumask))
 		return false;
+	if (!cpumask_equal(a->__pod_cpumask, b->__pod_cpumask))
+		return false;
+	if (a->affn_strict != b->affn_strict)
+		return false;
 	return true;
 }
 
+/* Update @attrs with actually available CPUs */
+static void wqattrs_actualize_cpumask(struct workqueue_attrs *attrs,
+				      const cpumask_t *unbound_cpumask)
+{
+	/*
+	 * Calculate the effective CPU mask of @attrs given @unbound_cpumask. If
+	 * @attrs->cpumask doesn't overlap with @unbound_cpumask, we fallback to
+	 * @unbound_cpumask.
+	 */
+	cpumask_and(attrs->cpumask, attrs->cpumask, unbound_cpumask);
+	if (unlikely(cpumask_empty(attrs->cpumask)))
+		cpumask_copy(attrs->cpumask, unbound_cpumask);
+}
+
+/* find wq_pod_type to use for @attrs */
+static const struct wq_pod_type *
+wqattrs_pod_type(const struct workqueue_attrs *attrs)
+{
+	enum wq_affn_scope scope;
+	struct wq_pod_type *pt;
+
+	/* to synchronize access to wq_affn_dfl */
+	lockdep_assert_held(&wq_pool_mutex);
+
+	if (attrs->affn_scope == WQ_AFFN_DFL)
+		scope = wq_affn_dfl;
+	else
+		scope = attrs->affn_scope;
+
+	pt = &wq_pod_types[scope];
+
+	if (!WARN_ON_ONCE(attrs->affn_scope == WQ_AFFN_NR_TYPES) &&
+	    likely(pt->nr_pods))
+		return pt;
+
+	/*
+	 * Before workqueue_init_topology(), only SYSTEM is available which is
+	 * initialized in workqueue_init_early().
+	 */
+	pt = &wq_pod_types[WQ_AFFN_SYSTEM];
+	BUG_ON(!pt->nr_pods);
+	return pt;
+}
+
 /**
  * init_worker_pool - initialize a newly zalloc'd worker_pool
  * @pool: worker_pool to initialize
@@ -3793,6 +3880,9 @@ static int init_worker_pool(struct worker_pool *pool)
 	pool->attrs = alloc_workqueue_attrs();
 	if (!pool->attrs)
 		return -ENOMEM;
+
+	wqattrs_clear_for_pool(pool->attrs);
+
 	return 0;
 }
 
@@ -3840,12 +3930,8 @@ static void rcu_free_wq(struct rcu_head *rcu)
 		container_of(rcu, struct workqueue_struct, rcu);
 
 	wq_free_lockdep(wq);
-
-	if (!(wq->flags & WQ_UNBOUND))
-		free_percpu(wq->cpu_pwqs);
-	else
+	free_percpu(wq->cpu_pwq);
 	free_workqueue_attrs(wq->unbound_attrs);
-
 	kfree(wq);
 }
 
@@ -3872,10 +3958,8 @@ static void rcu_free_pool(struct rcu_head *rcu)
 static void put_unbound_pool(struct worker_pool *pool)
 {
 	DECLARE_COMPLETION_ONSTACK(detach_completion);
-	struct list_head cull_list;
 	struct worker *worker;
-
-	INIT_LIST_HEAD(&cull_list);
+	LIST_HEAD(cull_list);
 
 	lockdep_assert_held(&wq_pool_mutex);
 
@@ -3959,10 +4043,10 @@ static void put_unbound_pool(struct worker_pool *pool)
  */
 static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
 {
+	struct wq_pod_type *pt = &wq_pod_types[WQ_AFFN_NUMA];
 	u32 hash = wqattrs_hash(attrs);
 	struct worker_pool *pool;
-	int node;
-	int target_node = NUMA_NO_NODE;
+	int pod, node = NUMA_NO_NODE;
 
 	lockdep_assert_held(&wq_pool_mutex);
 
@@ -3974,31 +4058,22 @@ static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
 		}
 	}
 
-	/* if cpumask is contained inside a NUMA node, we belong to that node */
-	if (wq_numa_enabled) {
-		for_each_node(node) {
-			if (cpumask_subset(attrs->cpumask,
-					   wq_numa_possible_cpumask[node])) {
-				target_node = node;
+	/* If __pod_cpumask is contained inside a NUMA pod, that's our node */
+	for (pod = 0; pod < pt->nr_pods; pod++) {
+		if (cpumask_subset(attrs->__pod_cpumask, pt->pod_cpus[pod])) {
+			node = pt->pod_node[pod];
 			break;
 		}
 	}
-	}
 
 	/* nope, create a new one */
-	pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, target_node);
+	pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, node);
 	if (!pool || init_worker_pool(pool) < 0)
 		goto fail;
 
-	lockdep_set_subclass(&pool->lock, 1);	/* see put_pwq() */
+	pool->node = node;
 	copy_workqueue_attrs(pool->attrs, attrs);
-	pool->node = target_node;
-
-	/*
-	 * no_numa isn't a worker_pool attribute, always clear it.  See
-	 * 'struct workqueue_attrs' comments for detail.
-	 */
-	pool->attrs->no_numa = false;
+	wqattrs_clear_for_pool(pool->attrs);
 
 	if (worker_pool_assign_id(pool) < 0)
 		goto fail;
@@ -4024,34 +4099,33 @@ static void rcu_free_pwq(struct rcu_head *rcu)
 }
 
 /*
- * Scheduled on system_wq by put_pwq() when an unbound pwq hits zero refcnt
- * and needs to be destroyed.
+ * Scheduled on pwq_release_worker by put_pwq() when an unbound pwq hits zero
+ * refcnt and needs to be destroyed.
  */
-static void pwq_unbound_release_workfn(struct work_struct *work)
+static void pwq_release_workfn(struct kthread_work *work)
 {
 	struct pool_workqueue *pwq = container_of(work, struct pool_workqueue,
-						  unbound_release_work);
+						  release_work);
 	struct workqueue_struct *wq = pwq->wq;
 	struct worker_pool *pool = pwq->pool;
 	bool is_last = false;
 
 	/*
-	 * when @pwq is not linked, it doesn't hold any reference to the
+	 * When @pwq is not linked, it doesn't hold any reference to the
 	 * @wq, and @wq is invalid to access.
 	 */
 	if (!list_empty(&pwq->pwqs_node)) {
-		if (WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND)))
-			return;
-
 		mutex_lock(&wq->mutex);
 		list_del_rcu(&pwq->pwqs_node);
 		is_last = list_empty(&wq->pwqs);
 		mutex_unlock(&wq->mutex);
 	}
 
+	if (wq->flags & WQ_UNBOUND) {
 		mutex_lock(&wq_pool_mutex);
 		put_unbound_pool(pool);
 		mutex_unlock(&wq_pool_mutex);
+	}
 
 	call_rcu(&pwq->rcu, rcu_free_pwq);
 
@@ -4095,24 +4169,13 @@ static void pwq_adjust_max_active(struct pool_workqueue *pwq)
 	 * is updated and visible.
 	 */
 	if (!freezable || !workqueue_freezing) {
-		bool kick = false;
-
 		pwq->max_active = wq->saved_max_active;
 
 		while (!list_empty(&pwq->inactive_works) &&
-		       pwq->nr_active < pwq->max_active) {
+		       pwq->nr_active < pwq->max_active)
 			pwq_activate_first_inactive(pwq);
-			kick = true;
-		}
 
-		/*
-		 * Need to kick a worker after thawed or an unbound wq's
-		 * max_active is bumped. In realtime scenarios, always kicking a
-		 * worker will cause interference on the isolated cpu cores, so
-		 * let's kick iff work items were activated.
-		 */
-		if (kick)
-			wake_up_worker(pwq->pool);
+		kick_pool(pwq->pool);
 	} else {
 		pwq->max_active = 0;
 	}
@@ -4135,7 +4198,7 @@ static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
 	INIT_LIST_HEAD(&pwq->inactive_works);
 	INIT_LIST_HEAD(&pwq->pwqs_node);
 	INIT_LIST_HEAD(&pwq->mayday_node);
-	INIT_WORK(&pwq->unbound_release_work, pwq_unbound_release_workfn);
+	kthread_init_work(&pwq->release_work, pwq_release_workfn);
 }
 
 /* sync @pwq with the current state of its associated wq and link it */
@@ -4183,61 +4246,49 @@ static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq,
 }
 
 /**
- * wq_calc_node_cpumask - calculate a wq_attrs' cpumask for the specified node
+ * wq_calc_pod_cpumask - calculate a wq_attrs' cpumask for a pod
  * @attrs: the wq_attrs of the default pwq of the target workqueue
- * @node: the target NUMA node
+ * @cpu: the target CPU
  * @cpu_going_down: if >= 0, the CPU to consider as offline
- * @cpumask: outarg, the resulting cpumask
  *
- * Calculate the cpumask a workqueue with @attrs should use on @node.  If
- * @cpu_going_down is >= 0, that cpu is considered offline during
- * calculation.  The result is stored in @cpumask.
+ * Calculate the cpumask a workqueue with @attrs should use on @pod. If
+ * @cpu_going_down is >= 0, that cpu is considered offline during calculation.
+ * The result is stored in @attrs->__pod_cpumask.
  *
- * If NUMA affinity is not enabled, @attrs->cpumask is always used.  If
- * enabled and @node has online CPUs requested by @attrs, the returned
- * cpumask is the intersection of the possible CPUs of @node and
- * @attrs->cpumask.
+ * If pod affinity is not enabled, @attrs->cpumask is always used. If enabled
+ * and @pod has online CPUs requested by @attrs, the returned cpumask is the
+ * intersection of the possible CPUs of @pod and @attrs->cpumask.
  *
- * The caller is responsible for ensuring that the cpumask of @node stays
- * stable.
- *
- * Return: %true if the resulting @cpumask is different from @attrs->cpumask,
- * %false if equal.
+ * The caller is responsible for ensuring that the cpumask of @pod stays stable.
  */
-static bool wq_calc_node_cpumask(const struct workqueue_attrs *attrs, int node,
-				 int cpu_going_down, cpumask_t *cpumask)
+static void wq_calc_pod_cpumask(struct workqueue_attrs *attrs, int cpu,
+				int cpu_going_down)
 {
-	if (!wq_numa_enabled || attrs->no_numa)
-		goto use_dfl;
+	const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
+	int pod = pt->cpu_pod[cpu];
 
-	/* does @node have any online CPUs @attrs wants? */
-	cpumask_and(cpumask, cpumask_of_node(node), attrs->cpumask);
+	/* does @pod have any online CPUs @attrs wants? */
+	cpumask_and(attrs->__pod_cpumask, pt->pod_cpus[pod], attrs->cpumask);
+	cpumask_and(attrs->__pod_cpumask, attrs->__pod_cpumask, cpu_online_mask);
 	if (cpu_going_down >= 0)
-		cpumask_clear_cpu(cpu_going_down, cpumask);
+		cpumask_clear_cpu(cpu_going_down, attrs->__pod_cpumask);
 
-	if (cpumask_empty(cpumask))
-		goto use_dfl;
+	if (cpumask_empty(attrs->__pod_cpumask)) {
+		cpumask_copy(attrs->__pod_cpumask, attrs->cpumask);
+		return;
+	}
 
-	/* yeap, return possible CPUs in @node that @attrs wants */
-	cpumask_and(cpumask, attrs->cpumask, wq_numa_possible_cpumask[node]);
+	/* yeap, return possible CPUs in @pod that @attrs wants */
+	cpumask_and(attrs->__pod_cpumask, attrs->cpumask, pt->pod_cpus[pod]);
 
-	if (cpumask_empty(cpumask)) {
+	if (cpumask_empty(attrs->__pod_cpumask))
 		pr_warn_once("WARNING: workqueue cpumask: online intersect > "
 				"possible intersect\n");
-		return false;
-	}
-
-	return !cpumask_equal(cpumask, attrs->cpumask);
-
-use_dfl:
-	cpumask_copy(cpumask, attrs->cpumask);
-	return false;
 }
 
-/* install @pwq into @wq's numa_pwq_tbl[] for @node and return the old pwq */
-static struct pool_workqueue *numa_pwq_tbl_install(struct workqueue_struct *wq,
-						   int node,
-						   struct pool_workqueue *pwq)
+/* install @pwq into @wq's cpu_pwq and return the old pwq */
+static struct pool_workqueue *install_unbound_pwq(struct workqueue_struct *wq,
+					int cpu, struct pool_workqueue *pwq)
 {
 	struct pool_workqueue *old_pwq;
 
@@ -4247,8 +4298,8 @@ static struct pool_workqueue *numa_pwq_tbl_install(struct workqueue_struct *wq,
 	/* link_pwq() can handle duplicate calls */
 	link_pwq(pwq);
 
-	old_pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
-	rcu_assign_pointer(wq->numa_pwq_tbl[node], pwq);
+	old_pwq = rcu_access_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu));
+	rcu_assign_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu), pwq);
 	return old_pwq;
 }
 
@@ -4265,10 +4316,10 @@ struct apply_wqattrs_ctx {
 static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx)
 {
 	if (ctx) {
-		int node;
+		int cpu;
 
-		for_each_node(node)
-			put_pwq_unlocked(ctx->pwq_tbl[node]);
+		for_each_possible_cpu(cpu)
+			put_pwq_unlocked(ctx->pwq_tbl[cpu]);
 		put_pwq_unlocked(ctx->dfl_pwq);
 
 		free_workqueue_attrs(ctx->attrs);
@@ -4284,76 +4335,64 @@ apply_wqattrs_prepare(struct workqueue_struct *wq,
 		      const cpumask_var_t unbound_cpumask)
 {
 	struct apply_wqattrs_ctx *ctx;
-	struct workqueue_attrs *new_attrs, *tmp_attrs;
-	int node;
+	struct workqueue_attrs *new_attrs;
+	int cpu;
 
 	lockdep_assert_held(&wq_pool_mutex);
 
-	ctx = kzalloc(struct_size(ctx, pwq_tbl, nr_node_ids), GFP_KERNEL);
+	if (WARN_ON(attrs->affn_scope < 0 ||
+		    attrs->affn_scope >= WQ_AFFN_NR_TYPES))
+		return ERR_PTR(-EINVAL);
+
+	ctx = kzalloc(struct_size(ctx, pwq_tbl, nr_cpu_ids), GFP_KERNEL);
 
 	new_attrs = alloc_workqueue_attrs();
-	tmp_attrs = alloc_workqueue_attrs();
-	if (!ctx || !new_attrs || !tmp_attrs)
+	if (!ctx || !new_attrs)
 		goto out_free;
 
-	/*
-	 * Calculate the attrs of the default pwq with unbound_cpumask
-	 * which is wq_unbound_cpumask or to set to wq_unbound_cpumask.
-	 * If the user configured cpumask doesn't overlap with the
-	 * wq_unbound_cpumask, we fallback to the wq_unbound_cpumask.
-	 */
-	copy_workqueue_attrs(new_attrs, attrs);
-	cpumask_and(new_attrs->cpumask, new_attrs->cpumask, unbound_cpumask);
-	if (unlikely(cpumask_empty(new_attrs->cpumask)))
-		cpumask_copy(new_attrs->cpumask, unbound_cpumask);
-
-	/*
-	 * We may create multiple pwqs with differing cpumasks.  Make a
-	 * copy of @new_attrs which will be modified and used to obtain
-	 * pools.
-	 */
-	copy_workqueue_attrs(tmp_attrs, new_attrs);
-
 	/*
 	 * If something goes wrong during CPU up/down, we'll fall back to
 	 * the default pwq covering whole @attrs->cpumask.  Always create
 	 * it even if we don't use it immediately.
 	 */
+	copy_workqueue_attrs(new_attrs, attrs);
+	wqattrs_actualize_cpumask(new_attrs, unbound_cpumask);
+	cpumask_copy(new_attrs->__pod_cpumask, new_attrs->cpumask);
 	ctx->dfl_pwq = alloc_unbound_pwq(wq, new_attrs);
 	if (!ctx->dfl_pwq)
 		goto out_free;
 
-	for_each_node(node) {
-		if (wq_calc_node_cpumask(new_attrs, node, -1, tmp_attrs->cpumask)) {
-			ctx->pwq_tbl[node] = alloc_unbound_pwq(wq, tmp_attrs);
-			if (!ctx->pwq_tbl[node])
-				goto out_free;
-		} else {
+	for_each_possible_cpu(cpu) {
+		if (new_attrs->ordered) {
 			ctx->dfl_pwq->refcnt++;
-			ctx->pwq_tbl[node] = ctx->dfl_pwq;
+			ctx->pwq_tbl[cpu] = ctx->dfl_pwq;
+		} else {
+			wq_calc_pod_cpumask(new_attrs, cpu, -1);
+			ctx->pwq_tbl[cpu] = alloc_unbound_pwq(wq, new_attrs);
+			if (!ctx->pwq_tbl[cpu])
+				goto out_free;
 		}
 	}
 
 	/* save the user configured attrs and sanitize it. */
 	copy_workqueue_attrs(new_attrs, attrs);
 	cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
+	cpumask_copy(new_attrs->__pod_cpumask, new_attrs->cpumask);
 	ctx->attrs = new_attrs;
 
 	ctx->wq = wq;
-	free_workqueue_attrs(tmp_attrs);
 	return ctx;
 
 out_free:
-	free_workqueue_attrs(tmp_attrs);
 	free_workqueue_attrs(new_attrs);
 	apply_wqattrs_cleanup(ctx);
-	return NULL;
+	return ERR_PTR(-ENOMEM);
 }
 
 /* set attrs and install prepared pwqs, @ctx points to old pwqs on return */
 static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
 {
-	int node;
+	int cpu;
 
 	/* all pwqs have been created successfully, let's install'em */
 	mutex_lock(&ctx->wq->mutex);
@@ -4361,9 +4400,9 @@ static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
 	copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs);
 
 	/* save the previous pwq and install the new one */
-	for_each_node(node)
-		ctx->pwq_tbl[node] = numa_pwq_tbl_install(ctx->wq, node,
-							  ctx->pwq_tbl[node]);
+	for_each_possible_cpu(cpu)
+		ctx->pwq_tbl[cpu] = install_unbound_pwq(ctx->wq, cpu,
+							ctx->pwq_tbl[cpu]);
 
 	/* @dfl_pwq might not have been used, ensure it's linked */
 	link_pwq(ctx->dfl_pwq);
@@ -4403,8 +4442,8 @@ static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
 	}
 
 	ctx = apply_wqattrs_prepare(wq, attrs, wq_unbound_cpumask);
-	if (!ctx)
-		return -ENOMEM;
+	if (IS_ERR(ctx))
+		return PTR_ERR(ctx);
 
 	/* the ctx has been prepared successfully, let's commit it */
 	apply_wqattrs_commit(ctx);
@@ -4418,12 +4457,11 @@ static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
  * @wq: the target workqueue
  * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
  *
- * Apply @attrs to an unbound workqueue @wq.  Unless disabled, on NUMA
- * machines, this function maps a separate pwq to each NUMA node with
- * possibles CPUs in @attrs->cpumask so that work items are affine to the
- * NUMA node it was issued on.  Older pwqs are released as in-flight work
- * items finish.  Note that a work item which repeatedly requeues itself
- * back-to-back will stay on its current pwq.
+ * Apply @attrs to an unbound workqueue @wq. Unless disabled, this function maps
+ * a separate pwq to each CPU pod with possibles CPUs in @attrs->cpumask so that
+ * work items are affine to the pod it was issued on. Older pwqs are released as
+ * in-flight work items finish. Note that a work item which repeatedly requeues
+ * itself back-to-back will stay on its current pwq.
  *
  * Performs GFP_KERNEL allocations.
  *
@@ -4446,40 +4484,37 @@ int apply_workqueue_attrs(struct workqueue_struct *wq,
 }
 
 /**
- * wq_update_unbound_numa - update NUMA affinity of a wq for CPU hot[un]plug
+ * wq_update_pod - update pod affinity of a wq for CPU hot[un]plug
  * @wq: the target workqueue
- * @cpu: the CPU coming up or going down
+ * @cpu: the CPU to update pool association for
+ * @hotplug_cpu: the CPU coming up or going down
  * @online: whether @cpu is coming up or going down
  *
  * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and
- * %CPU_DOWN_FAILED.  @cpu is being hot[un]plugged, update NUMA affinity of
+ * %CPU_DOWN_FAILED.  @cpu is being hot[un]plugged, update pod affinity of
  * @wq accordingly.
  *
- * If NUMA affinity can't be adjusted due to memory allocation failure, it
- * falls back to @wq->dfl_pwq which may not be optimal but is always
- * correct.
  *
- * Note that when the last allowed CPU of a NUMA node goes offline for a
- * workqueue with a cpumask spanning multiple nodes, the workers which were
- * already executing the work items for the workqueue will lose their CPU
- * affinity and may execute on any CPU.  This is similar to how per-cpu
- * workqueues behave on CPU_DOWN.  If a workqueue user wants strict
- * affinity, it's the user's responsibility to flush the work item from
- * CPU_DOWN_PREPARE.
+ * If pod affinity can't be adjusted due to memory allocation failure, it falls
+ * back to @wq->dfl_pwq which may not be optimal but is always correct.
+ *
+ * Note that when the last allowed CPU of a pod goes offline for a workqueue
+ * with a cpumask spanning multiple pods, the workers which were already
+ * executing the work items for the workqueue will lose their CPU affinity and
+ * may execute on any CPU. This is similar to how per-cpu workqueues behave on
+ * CPU_DOWN. If a workqueue user wants strict affinity, it's the user's
+ * responsibility to flush the work item from CPU_DOWN_PREPARE.
  */
-static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu,
-				   bool online)
+static void wq_update_pod(struct workqueue_struct *wq, int cpu,
+			  int hotplug_cpu, bool online)
 {
-	int node = cpu_to_node(cpu);
-	int cpu_off = online ? -1 : cpu;
+	int off_cpu = online ? -1 : hotplug_cpu;
 	struct pool_workqueue *old_pwq = NULL, *pwq;
 	struct workqueue_attrs *target_attrs;
-	cpumask_t *cpumask;
 
 	lockdep_assert_held(&wq_pool_mutex);
 
-	if (!wq_numa_enabled || !(wq->flags & WQ_UNBOUND) ||
-	    wq->unbound_attrs->no_numa)
+	if (!(wq->flags & WQ_UNBOUND) || wq->unbound_attrs->ordered)
 		return;
 
 	/*
@@ -4487,36 +4522,29 @@ static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu,
 	 * Let's use a preallocated one.  The following buf is protected by
 	 * CPU hotplug exclusion.
 	 */
-	target_attrs = wq_update_unbound_numa_attrs_buf;
-	cpumask = target_attrs->cpumask;
+	target_attrs = wq_update_pod_attrs_buf;
 
 	copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
-	pwq = unbound_pwq_by_node(wq, node);
+	wqattrs_actualize_cpumask(target_attrs, wq_unbound_cpumask);
 
-	/*
-	 * Let's determine what needs to be done.  If the target cpumask is
-	 * different from the default pwq's, we need to compare it to @pwq's
-	 * and create a new one if they don't match.  If the target cpumask
-	 * equals the default pwq's, the default pwq should be used.
-	 */
-	if (wq_calc_node_cpumask(wq->dfl_pwq->pool->attrs, node, cpu_off, cpumask)) {
-		if (cpumask_equal(cpumask, pwq->pool->attrs->cpumask))
+	/* nothing to do if the target cpumask matches the current pwq */
+	wq_calc_pod_cpumask(target_attrs, cpu, off_cpu);
+	pwq = rcu_dereference_protected(*per_cpu_ptr(wq->cpu_pwq, cpu),
+					lockdep_is_held(&wq_pool_mutex));
+	if (wqattrs_equal(target_attrs, pwq->pool->attrs))
 		return;
-	} else {
-		goto use_dfl_pwq;
-	}
 
 	/* create a new pwq */
 	pwq = alloc_unbound_pwq(wq, target_attrs);
 	if (!pwq) {
-		pr_warn("workqueue: allocation failed while updating NUMA affinity of \"%s\"\n",
+		pr_warn("workqueue: allocation failed while updating CPU pod affinity of \"%s\"\n",
 			wq->name);
 		goto use_dfl_pwq;
 	}
 
 	/* Install the new pwq. */
 	mutex_lock(&wq->mutex);
-	old_pwq = numa_pwq_tbl_install(wq, node, pwq);
+	old_pwq = install_unbound_pwq(wq, cpu, pwq);
 	goto out_unlock;
 
 use_dfl_pwq:
@@ -4524,7 +4552,7 @@ static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu,
 	raw_spin_lock_irq(&wq->dfl_pwq->pool->lock);
 	get_pwq(wq->dfl_pwq);
 	raw_spin_unlock_irq(&wq->dfl_pwq->pool->lock);
-	old_pwq = numa_pwq_tbl_install(wq, node, wq->dfl_pwq);
+	old_pwq = install_unbound_pwq(wq, cpu, wq->dfl_pwq);
 out_unlock:
 	mutex_unlock(&wq->mutex);
 	put_pwq_unlocked(old_pwq);
@@ -4535,21 +4563,26 @@ static int alloc_and_link_pwqs(struct workqueue_struct *wq)
 	bool highpri = wq->flags & WQ_HIGHPRI;
 	int cpu, ret;
 
-	if (!(wq->flags & WQ_UNBOUND)) {
-		wq->cpu_pwqs = alloc_percpu(struct pool_workqueue);
-		if (!wq->cpu_pwqs)
-			return -ENOMEM;
+	wq->cpu_pwq = alloc_percpu(struct pool_workqueue *);
+	if (!wq->cpu_pwq)
+		goto enomem;
 
+	if (!(wq->flags & WQ_UNBOUND)) {
 		for_each_possible_cpu(cpu) {
-			struct pool_workqueue *pwq =
-				per_cpu_ptr(wq->cpu_pwqs, cpu);
-			struct worker_pool *cpu_pools =
-				per_cpu(cpu_worker_pools, cpu);
+			struct pool_workqueue **pwq_p =
+				per_cpu_ptr(wq->cpu_pwq, cpu);
+			struct worker_pool *pool =
+				&(per_cpu_ptr(cpu_worker_pools, cpu)[highpri]);
 
-			init_pwq(pwq, wq, &cpu_pools[highpri]);
+			*pwq_p = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL,
+						       pool->node);
+			if (!*pwq_p)
+				goto enomem;
+
+			init_pwq(*pwq_p, wq, pool);
 
 			mutex_lock(&wq->mutex);
-			link_pwq(pwq);
+			link_pwq(*pwq_p);
 			mutex_unlock(&wq->mutex);
 		}
 		return 0;
@@ -4568,18 +4601,25 @@ static int alloc_and_link_pwqs(struct workqueue_struct *wq)
 	cpus_read_unlock();
 
 	return ret;
+
+enomem:
+	if (wq->cpu_pwq) {
+		for_each_possible_cpu(cpu)
+			kfree(*per_cpu_ptr(wq->cpu_pwq, cpu));
+		free_percpu(wq->cpu_pwq);
+		wq->cpu_pwq = NULL;
+	}
+	return -ENOMEM;
 }
 
 static int wq_clamp_max_active(int max_active, unsigned int flags,
 			       const char *name)
 {
-	int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE;
-
-	if (max_active < 1 || max_active > lim)
+	if (max_active < 1 || max_active > WQ_MAX_ACTIVE)
 		pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
-			max_active, name, 1, lim);
+			max_active, name, 1, WQ_MAX_ACTIVE);
 
-	return clamp_val(max_active, 1, lim);
+	return clamp_val(max_active, 1, WQ_MAX_ACTIVE);
 }
 
 /*
@@ -4602,7 +4642,7 @@ static int init_rescuer(struct workqueue_struct *wq)
 	}
 
 	rescuer->rescue_wq = wq;
-	rescuer->task = kthread_create(rescuer_thread, rescuer, "%s", wq->name);
+	rescuer->task = kthread_create(rescuer_thread, rescuer, "kworker/R-%s", wq->name);
 	if (IS_ERR(rescuer->task)) {
 		ret = PTR_ERR(rescuer->task);
 		pr_err("workqueue: Failed to create a rescuer kthread for wq \"%s\": %pe",
@@ -4623,17 +4663,15 @@ struct workqueue_struct *alloc_workqueue(const char *fmt,
 					 unsigned int flags,
 					 int max_active, ...)
 {
-	size_t tbl_size = 0;
 	va_list args;
 	struct workqueue_struct *wq;
 	struct pool_workqueue *pwq;
 
 	/*
-	 * Unbound && max_active == 1 used to imply ordered, which is no
-	 * longer the case on NUMA machines due to per-node pools.  While
+	 * Unbound && max_active == 1 used to imply ordered, which is no longer
+	 * the case on many machines due to per-pod pools. While
 	 * alloc_ordered_workqueue() is the right way to create an ordered
-	 * workqueue, keep the previous behavior to avoid subtle breakages
-	 * on NUMA.
+	 * workqueue, keep the previous behavior to avoid subtle breakages.
 	 */
 	if ((flags & WQ_UNBOUND) && max_active == 1)
 		flags |= __WQ_ORDERED;
@@ -4643,10 +4681,7 @@ struct workqueue_struct *alloc_workqueue(const char *fmt,
 		flags |= WQ_UNBOUND;
 
 	/* allocate wq and format name */
-	if (flags & WQ_UNBOUND)
-		tbl_size = nr_node_ids * sizeof(wq->numa_pwq_tbl[0]);
-
-	wq = kzalloc(sizeof(*wq) + tbl_size, GFP_KERNEL);
+	wq = kzalloc(sizeof(*wq), GFP_KERNEL);
 	if (!wq)
 		return NULL;
 
@@ -4741,7 +4776,7 @@ static bool pwq_busy(struct pool_workqueue *pwq)
 void destroy_workqueue(struct workqueue_struct *wq)
 {
 	struct pool_workqueue *pwq;
-	int node;
+	int cpu;
 
 	/*
 	 * Remove it from sysfs first so that sanity check failure doesn't
@@ -4800,33 +4835,23 @@ void destroy_workqueue(struct workqueue_struct *wq)
 	list_del_rcu(&wq->list);
 	mutex_unlock(&wq_pool_mutex);
 
-	if (!(wq->flags & WQ_UNBOUND)) {
-		wq_unregister_lockdep(wq);
-		/*
-		 * The base ref is never dropped on per-cpu pwqs.  Directly
-		 * schedule RCU free.
-		 */
-		call_rcu(&wq->rcu, rcu_free_wq);
-	} else {
 	/*
-		 * We're the sole accessor of @wq at this point.  Directly
-		 * access numa_pwq_tbl[] and dfl_pwq to put the base refs.
-		 * @wq will be freed when the last pwq is released.
+	 * We're the sole accessor of @wq. Directly access cpu_pwq and dfl_pwq
+	 * to put the base refs. @wq will be auto-destroyed from the last
+	 * pwq_put. RCU read lock prevents @wq from going away from under us.
 	 */
-		for_each_node(node) {
-			pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
-			RCU_INIT_POINTER(wq->numa_pwq_tbl[node], NULL);
+	rcu_read_lock();
+
+	for_each_possible_cpu(cpu) {
+		pwq = rcu_access_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu));
+		RCU_INIT_POINTER(*per_cpu_ptr(wq->cpu_pwq, cpu), NULL);
 		put_pwq_unlocked(pwq);
 	}
 
-		/*
-		 * Put dfl_pwq.  @wq may be freed any time after dfl_pwq is
-		 * put.  Don't access it afterwards.
-		 */
-		pwq = wq->dfl_pwq;
+	put_pwq_unlocked(wq->dfl_pwq);
 	wq->dfl_pwq = NULL;
-		put_pwq_unlocked(pwq);
-	}
+
+	rcu_read_unlock();
 }
 EXPORT_SYMBOL_GPL(destroy_workqueue);
 
@@ -4903,10 +4928,11 @@ bool current_is_workqueue_rescuer(void)
  * unreliable and only useful as advisory hints or for debugging.
  *
  * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU.
- * Note that both per-cpu and unbound workqueues may be associated with
- * multiple pool_workqueues which have separate congested states.  A
- * workqueue being congested on one CPU doesn't mean the workqueue is also
- * contested on other CPUs / NUMA nodes.
+ *
+ * With the exception of ordered workqueues, all workqueues have per-cpu
+ * pool_workqueues, each with its own congested state. A workqueue being
+ * congested on one CPU doesn't mean that the workqueue is contested on any
+ * other CPUs.
  *
  * Return:
  * %true if congested, %false otherwise.
@@ -4922,12 +4948,9 @@ bool workqueue_congested(int cpu, struct workqueue_struct *wq)
 	if (cpu == WORK_CPU_UNBOUND)
 		cpu = smp_processor_id();
 
-	if (!(wq->flags & WQ_UNBOUND))
-		pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
-	else
-		pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
-
+	pwq = *per_cpu_ptr(wq->cpu_pwq, cpu);
 	ret = !list_empty(&pwq->inactive_works);
+
 	preempt_enable();
 	rcu_read_unlock();
 
@@ -5402,7 +5425,7 @@ static void unbind_workers(int cpu)
 		 * worker blocking could lead to lengthy stalls.  Kick off
 		 * unbound chain execution of currently pending work items.
 		 */
-		wake_up_worker(pool);
+		kick_pool(pool);
 
 		raw_spin_unlock_irq(&pool->lock);
 
@@ -5435,7 +5458,7 @@ static void rebind_workers(struct worker_pool *pool)
 	for_each_pool_worker(worker, pool) {
 		kthread_set_per_cpu(worker->task, pool->cpu);
 		WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
-						  pool->attrs->cpumask) < 0);
+						  pool_allowed_cpus(pool)) < 0);
 	}
 
 	raw_spin_lock_irq(&pool->lock);
@@ -5529,9 +5552,18 @@ int workqueue_online_cpu(unsigned int cpu)
 		mutex_unlock(&wq_pool_attach_mutex);
 	}
 
-	/* update NUMA affinity of unbound workqueues */
-	list_for_each_entry(wq, &workqueues, list)
-		wq_update_unbound_numa(wq, cpu, true);
+	/* update pod affinity of unbound workqueues */
+	list_for_each_entry(wq, &workqueues, list) {
+		struct workqueue_attrs *attrs = wq->unbound_attrs;
+
+		if (attrs) {
+			const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
+			int tcpu;
+
+			for_each_cpu(tcpu, pt->pod_cpus[pt->cpu_pod[cpu]])
+				wq_update_pod(wq, tcpu, cpu, true);
+		}
+	}
 
 	mutex_unlock(&wq_pool_mutex);
 	return 0;
@@ -5547,10 +5579,19 @@ int workqueue_offline_cpu(unsigned int cpu)
 
 	unbind_workers(cpu);
 
-	/* update NUMA affinity of unbound workqueues */
+	/* update pod affinity of unbound workqueues */
 	mutex_lock(&wq_pool_mutex);
-	list_for_each_entry(wq, &workqueues, list)
-		wq_update_unbound_numa(wq, cpu, false);
+	list_for_each_entry(wq, &workqueues, list) {
+		struct workqueue_attrs *attrs = wq->unbound_attrs;
+
+		if (attrs) {
+			const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
+			int tcpu;
+
+			for_each_cpu(tcpu, pt->pod_cpus[pt->cpu_pod[cpu]])
+				wq_update_pod(wq, tcpu, cpu, false);
+		}
+	}
 	mutex_unlock(&wq_pool_mutex);
 
 	return 0;
@@ -5746,8 +5787,8 @@ static int workqueue_apply_unbound_cpumask(const cpumask_var_t unbound_cpumask)
 			continue;
 
 		ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs, unbound_cpumask);
-		if (!ctx) {
-			ret = -ENOMEM;
+		if (IS_ERR(ctx)) {
+			ret = PTR_ERR(ctx);
 			break;
 		}
 
@@ -5805,6 +5846,57 @@ int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
 	return ret;
 }
 
+static int parse_affn_scope(const char *val)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(wq_affn_names); i++) {
+		if (!strncasecmp(val, wq_affn_names[i], strlen(wq_affn_names[i])))
+			return i;
+	}
+	return -EINVAL;
+}
+
+static int wq_affn_dfl_set(const char *val, const struct kernel_param *kp)
+{
+	struct workqueue_struct *wq;
+	int affn, cpu;
+
+	affn = parse_affn_scope(val);
+	if (affn < 0)
+		return affn;
+	if (affn == WQ_AFFN_DFL)
+		return -EINVAL;
+
+	cpus_read_lock();
+	mutex_lock(&wq_pool_mutex);
+
+	wq_affn_dfl = affn;
+
+	list_for_each_entry(wq, &workqueues, list) {
+		for_each_online_cpu(cpu) {
+			wq_update_pod(wq, cpu, cpu, true);
+		}
+	}
+
+	mutex_unlock(&wq_pool_mutex);
+	cpus_read_unlock();
+
+	return 0;
+}
+
+static int wq_affn_dfl_get(char *buffer, const struct kernel_param *kp)
+{
+	return scnprintf(buffer, PAGE_SIZE, "%s\n", wq_affn_names[wq_affn_dfl]);
+}
+
+static const struct kernel_param_ops wq_affn_dfl_ops = {
+	.set	= wq_affn_dfl_set,
+	.get	= wq_affn_dfl_get,
+};
+
+module_param_cb(default_affinity_scope, &wq_affn_dfl_ops, NULL, 0644);
+
 #ifdef CONFIG_SYSFS
 /*
  * Workqueues with WQ_SYSFS flag set is visible to userland via
@@ -5816,10 +5908,10 @@ int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
  *
  * Unbound workqueues have the following extra attributes.
  *
- *  pool_ids	RO int	: the associated pool IDs for each node
  *  nice		RW int	: nice value of the workers
  *  cpumask		RW mask	: bitmask of allowed CPUs for the workers
- *  numa	RW bool	: whether enable NUMA affinity
+ *  affinity_scope	RW str  : worker CPU affinity scope (cache, numa, none)
+ *  affinity_strict	RW bool : worker CPU affinity is strict
  */
 struct wq_device {
 	struct workqueue_struct		*wq;
@@ -5872,28 +5964,6 @@ static struct attribute *wq_sysfs_attrs[] = {
 };
 ATTRIBUTE_GROUPS(wq_sysfs);
 
-static ssize_t wq_pool_ids_show(struct device *dev,
-				struct device_attribute *attr, char *buf)
-{
-	struct workqueue_struct *wq = dev_to_wq(dev);
-	const char *delim = "";
-	int node, written = 0;
-
-	cpus_read_lock();
-	rcu_read_lock();
-	for_each_node(node) {
-		written += scnprintf(buf + written, PAGE_SIZE - written,
-				     "%s%d:%d", delim, node,
-				     unbound_pwq_by_node(wq, node)->pool->id);
-		delim = " ";
-	}
-	written += scnprintf(buf + written, PAGE_SIZE - written, "\n");
-	rcu_read_unlock();
-	cpus_read_unlock();
-
-	return written;
-}
-
 static ssize_t wq_nice_show(struct device *dev, struct device_attribute *attr,
 			    char *buf)
 {
@@ -5984,50 +6054,84 @@ static ssize_t wq_cpumask_store(struct device *dev,
 	return ret ?: count;
 }
 
-static ssize_t wq_numa_show(struct device *dev, struct device_attribute *attr,
-			    char *buf)
+static ssize_t wq_affn_scope_show(struct device *dev,
+				  struct device_attribute *attr, char *buf)
 {
 	struct workqueue_struct *wq = dev_to_wq(dev);
 	int written;
 
 	mutex_lock(&wq->mutex);
-	written = scnprintf(buf, PAGE_SIZE, "%d\n",
-			    !wq->unbound_attrs->no_numa);
+	if (wq->unbound_attrs->affn_scope == WQ_AFFN_DFL)
+		written = scnprintf(buf, PAGE_SIZE, "%s (%s)\n",
+				    wq_affn_names[WQ_AFFN_DFL],
+				    wq_affn_names[wq_affn_dfl]);
+	else
+		written = scnprintf(buf, PAGE_SIZE, "%s\n",
+				    wq_affn_names[wq->unbound_attrs->affn_scope]);
 	mutex_unlock(&wq->mutex);
 
 	return written;
 }
 
-static ssize_t wq_numa_store(struct device *dev, struct device_attribute *attr,
+static ssize_t wq_affn_scope_store(struct device *dev,
+				   struct device_attribute *attr,
 				   const char *buf, size_t count)
 {
 	struct workqueue_struct *wq = dev_to_wq(dev);
 	struct workqueue_attrs *attrs;
-	int v, ret = -ENOMEM;
+	int affn, ret = -ENOMEM;
 
-	apply_wqattrs_lock();
+	affn = parse_affn_scope(buf);
+	if (affn < 0)
+		return affn;
 
+	apply_wqattrs_lock();
 	attrs = wq_sysfs_prep_attrs(wq);
-	if (!attrs)
-		goto out_unlock;
-
-	ret = -EINVAL;
-	if (sscanf(buf, "%d", &v) == 1) {
-		attrs->no_numa = !v;
+	if (attrs) {
+		attrs->affn_scope = affn;
 		ret = apply_workqueue_attrs_locked(wq, attrs);
 	}
+	apply_wqattrs_unlock();
+	free_workqueue_attrs(attrs);
+	return ret ?: count;
+}
 
-out_unlock:
+static ssize_t wq_affinity_strict_show(struct device *dev,
+				       struct device_attribute *attr, char *buf)
+{
+	struct workqueue_struct *wq = dev_to_wq(dev);
+
+	return scnprintf(buf, PAGE_SIZE, "%d\n",
+			 wq->unbound_attrs->affn_strict);
+}
+
+static ssize_t wq_affinity_strict_store(struct device *dev,
+					struct device_attribute *attr,
+					const char *buf, size_t count)
+{
+	struct workqueue_struct *wq = dev_to_wq(dev);
+	struct workqueue_attrs *attrs;
+	int v, ret = -ENOMEM;
+
+	if (sscanf(buf, "%d", &v) != 1)
+		return -EINVAL;
+
+	apply_wqattrs_lock();
+	attrs = wq_sysfs_prep_attrs(wq);
+	if (attrs) {
+		attrs->affn_strict = (bool)v;
+		ret = apply_workqueue_attrs_locked(wq, attrs);
+	}
 	apply_wqattrs_unlock();
 	free_workqueue_attrs(attrs);
 	return ret ?: count;
 }
 
 static struct device_attribute wq_sysfs_unbound_attrs[] = {
-	__ATTR(pool_ids, 0444, wq_pool_ids_show, NULL),
 	__ATTR(nice, 0644, wq_nice_show, wq_nice_store),
 	__ATTR(cpumask, 0644, wq_cpumask_show, wq_cpumask_store),
-	__ATTR(numa, 0644, wq_numa_show, wq_numa_store),
+	__ATTR(affinity_scope, 0644, wq_affn_scope_show, wq_affn_scope_store),
+	__ATTR(affinity_strict, 0644, wq_affinity_strict_show, wq_affinity_strict_store),
 	__ATTR_NULL,
 };
 
@@ -6393,62 +6497,19 @@ static inline void wq_watchdog_init(void) { }
 
 #endif	/* CONFIG_WQ_WATCHDOG */
 
-static void __init wq_numa_init(void)
-{
-	cpumask_var_t *tbl;
-	int node, cpu;
-
-	if (num_possible_nodes() <= 1)
-		return;
-
-	if (wq_disable_numa) {
-		pr_info("workqueue: NUMA affinity support disabled\n");
-		return;
-	}
-
-	for_each_possible_cpu(cpu) {
-		if (WARN_ON(cpu_to_node(cpu) == NUMA_NO_NODE)) {
-			pr_warn("workqueue: NUMA node mapping not available for cpu%d, disabling NUMA support\n", cpu);
-			return;
-		}
-	}
-
-	wq_update_unbound_numa_attrs_buf = alloc_workqueue_attrs();
-	BUG_ON(!wq_update_unbound_numa_attrs_buf);
-
-	/*
-	 * We want masks of possible CPUs of each node which isn't readily
-	 * available.  Build one from cpu_to_node() which should have been
-	 * fully initialized by now.
-	 */
-	tbl = kcalloc(nr_node_ids, sizeof(tbl[0]), GFP_KERNEL);
-	BUG_ON(!tbl);
-
-	for_each_node(node)
-		BUG_ON(!zalloc_cpumask_var_node(&tbl[node], GFP_KERNEL,
-				node_online(node) ? node : NUMA_NO_NODE));
-
-	for_each_possible_cpu(cpu) {
-		node = cpu_to_node(cpu);
-		cpumask_set_cpu(cpu, tbl[node]);
-	}
-
-	wq_numa_possible_cpumask = tbl;
-	wq_numa_enabled = true;
-}
-
 /**
  * workqueue_init_early - early init for workqueue subsystem
  *
- * This is the first half of two-staged workqueue subsystem initialization
- * and invoked as soon as the bare basics - memory allocation, cpumasks and
- * idr are up.  It sets up all the data structures and system workqueues
- * and allows early boot code to create workqueues and queue/cancel work
- * items.  Actual work item execution starts only after kthreads can be
- * created and scheduled right before early initcalls.
+ * This is the first step of three-staged workqueue subsystem initialization and
+ * invoked as soon as the bare basics - memory allocation, cpumasks and idr are
+ * up. It sets up all the data structures and system workqueues and allows early
+ * boot code to create workqueues and queue/cancel work items. Actual work item
+ * execution starts only after kthreads can be created and scheduled right
+ * before early initcalls.
  */
 void __init workqueue_init_early(void)
 {
+	struct wq_pod_type *pt = &wq_pod_types[WQ_AFFN_SYSTEM];
 	int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL };
 	int i, cpu;
 
@@ -6458,8 +6519,30 @@ void __init workqueue_init_early(void)
 	cpumask_copy(wq_unbound_cpumask, housekeeping_cpumask(HK_TYPE_WQ));
 	cpumask_and(wq_unbound_cpumask, wq_unbound_cpumask, housekeeping_cpumask(HK_TYPE_DOMAIN));
 
+	if (!cpumask_empty(&wq_cmdline_cpumask))
+		cpumask_and(wq_unbound_cpumask, wq_unbound_cpumask, &wq_cmdline_cpumask);
+
 	pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
 
+	wq_update_pod_attrs_buf = alloc_workqueue_attrs();
+	BUG_ON(!wq_update_pod_attrs_buf);
+
+	/* initialize WQ_AFFN_SYSTEM pods */
+	pt->pod_cpus = kcalloc(1, sizeof(pt->pod_cpus[0]), GFP_KERNEL);
+	pt->pod_node = kcalloc(1, sizeof(pt->pod_node[0]), GFP_KERNEL);
+	pt->cpu_pod = kcalloc(nr_cpu_ids, sizeof(pt->cpu_pod[0]), GFP_KERNEL);
+	BUG_ON(!pt->pod_cpus || !pt->pod_node || !pt->cpu_pod);
+
+	BUG_ON(!zalloc_cpumask_var_node(&pt->pod_cpus[0], GFP_KERNEL, NUMA_NO_NODE));
+
+	wq_update_pod_attrs_buf = alloc_workqueue_attrs();
+	BUG_ON(!wq_update_pod_attrs_buf);
+
+	pt->nr_pods = 1;
+	cpumask_copy(pt->pod_cpus[0], cpu_possible_mask);
+	pt->pod_node[0] = NUMA_NO_NODE;
+	pt->cpu_pod[0] = 0;
+
 	/* initialize CPU pools */
 	for_each_possible_cpu(cpu) {
 		struct worker_pool *pool;
@@ -6469,7 +6552,9 @@ void __init workqueue_init_early(void)
 			BUG_ON(init_worker_pool(pool));
 			pool->cpu = cpu;
 			cpumask_copy(pool->attrs->cpumask, cpumask_of(cpu));
+			cpumask_copy(pool->attrs->__pod_cpumask, cpumask_of(cpu));
 			pool->attrs->nice = std_nice[i++];
+			pool->attrs->affn_strict = true;
 			pool->node = cpu_to_node(cpu);
 
 			/* alloc pool ID */
@@ -6490,11 +6575,10 @@ void __init workqueue_init_early(void)
 		/*
 		 * An ordered wq should have only one pwq as ordering is
 		 * guaranteed by max_active which is enforced by pwqs.
-		 * Turn off NUMA so that dfl_pwq is used for all nodes.
 		 */
 		BUG_ON(!(attrs = alloc_workqueue_attrs()));
 		attrs->nice = std_nice[i];
-		attrs->no_numa = true;
+		attrs->ordered = true;
 		ordered_wq_attrs[i] = attrs;
 	}
 
@@ -6502,7 +6586,7 @@ void __init workqueue_init_early(void)
 	system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0);
 	system_long_wq = alloc_workqueue("events_long", 0, 0);
 	system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
-					    WQ_UNBOUND_MAX_ACTIVE);
+					    WQ_MAX_ACTIVE);
 	system_freezable_wq = alloc_workqueue("events_freezable",
 					      WQ_FREEZABLE, 0);
 	system_power_efficient_wq = alloc_workqueue("events_power_efficient",
@@ -6525,6 +6609,9 @@ static void __init wq_cpu_intensive_thresh_init(void)
 	if (wq_cpu_intensive_thresh_us != ULONG_MAX)
 		return;
 
+	pwq_release_worker = kthread_create_worker(0, "pool_workqueue_release");
+	BUG_ON(IS_ERR(pwq_release_worker));
+
 	/*
 	 * The default of 10ms is derived from the fact that most modern (as of
 	 * 2023) processors can do a lot in 10ms and that it's just below what
@@ -6555,11 +6642,11 @@ static void __init wq_cpu_intensive_thresh_init(void)
 /**
  * workqueue_init - bring workqueue subsystem fully online
  *
- * This is the latter half of two-staged workqueue subsystem initialization
- * and invoked as soon as kthreads can be created and scheduled.
- * Workqueues have been created and work items queued on them, but there
- * are no kworkers executing the work items yet.  Populate the worker pools
- * with the initial workers and enable future kworker creations.
+ * This is the second step of three-staged workqueue subsystem initialization
+ * and invoked as soon as kthreads can be created and scheduled. Workqueues have
+ * been created and work items queued on them, but there are no kworkers
+ * executing the work items yet. Populate the worker pools with the initial
+ * workers and enable future kworker creations.
  */
 void __init workqueue_init(void)
 {
@@ -6569,19 +6656,12 @@ void __init workqueue_init(void)
 
 	wq_cpu_intensive_thresh_init();
 
-	/*
-	 * It'd be simpler to initialize NUMA in workqueue_init_early() but
-	 * CPU to node mapping may not be available that early on some
-	 * archs such as power and arm64.  As per-cpu pools created
-	 * previously could be missing node hint and unbound pools NUMA
-	 * affinity, fix them up.
-	 *
-	 * Also, while iterating workqueues, create rescuers if requested.
-	 */
-	wq_numa_init();
-
 	mutex_lock(&wq_pool_mutex);
 
+	/*
+	 * Per-cpu pools created earlier could be missing node hint. Fix them
+	 * up. Also, create a rescuer for workqueues that requested it.
+	 */
 	for_each_possible_cpu(cpu) {
 		for_each_cpu_worker_pool(pool, cpu) {
 			pool->node = cpu_to_node(cpu);
@@ -6589,7 +6669,6 @@ void __init workqueue_init(void)
 	}
 
 	list_for_each_entry(wq, &workqueues, list) {
-		wq_update_unbound_numa(wq, smp_processor_id(), true);
 		WARN(init_rescuer(wq),
 		     "workqueue: failed to create early rescuer for %s",
 		     wq->name);
@@ -6613,9 +6692,114 @@ void __init workqueue_init(void)
 }
 
 /*
- * Despite the naming, this is a no-op function which is here only for avoiding
- * link error. Since compile-time warning may fail to catch, we will need to
- * emit run-time warning from __flush_workqueue().
+ * Initialize @pt by first initializing @pt->cpu_pod[] with pod IDs according to
+ * @cpu_shares_pod(). Each subset of CPUs that share a pod is assigned a unique
+ * and consecutive pod ID. The rest of @pt is initialized accordingly.
+ */
+static void __init init_pod_type(struct wq_pod_type *pt,
+				 bool (*cpus_share_pod)(int, int))
+{
+	int cur, pre, cpu, pod;
+
+	pt->nr_pods = 0;
+
+	/* init @pt->cpu_pod[] according to @cpus_share_pod() */
+	pt->cpu_pod = kcalloc(nr_cpu_ids, sizeof(pt->cpu_pod[0]), GFP_KERNEL);
+	BUG_ON(!pt->cpu_pod);
+
+	for_each_possible_cpu(cur) {
+		for_each_possible_cpu(pre) {
+			if (pre >= cur) {
+				pt->cpu_pod[cur] = pt->nr_pods++;
+				break;
+			}
+			if (cpus_share_pod(cur, pre)) {
+				pt->cpu_pod[cur] = pt->cpu_pod[pre];
+				break;
+			}
+		}
+	}
+
+	/* init the rest to match @pt->cpu_pod[] */
+	pt->pod_cpus = kcalloc(pt->nr_pods, sizeof(pt->pod_cpus[0]), GFP_KERNEL);
+	pt->pod_node = kcalloc(pt->nr_pods, sizeof(pt->pod_node[0]), GFP_KERNEL);
+	BUG_ON(!pt->pod_cpus || !pt->pod_node);
+
+	for (pod = 0; pod < pt->nr_pods; pod++)
+		BUG_ON(!zalloc_cpumask_var(&pt->pod_cpus[pod], GFP_KERNEL));
+
+	for_each_possible_cpu(cpu) {
+		cpumask_set_cpu(cpu, pt->pod_cpus[pt->cpu_pod[cpu]]);
+		pt->pod_node[pt->cpu_pod[cpu]] = cpu_to_node(cpu);
+	}
+}
+
+static bool __init cpus_dont_share(int cpu0, int cpu1)
+{
+	return false;
+}
+
+static bool __init cpus_share_smt(int cpu0, int cpu1)
+{
+#ifdef CONFIG_SCHED_SMT
+	return cpumask_test_cpu(cpu0, cpu_smt_mask(cpu1));
+#else
+	return false;
+#endif
+}
+
+static bool __init cpus_share_numa(int cpu0, int cpu1)
+{
+	return cpu_to_node(cpu0) == cpu_to_node(cpu1);
+}
+
+/**
+ * workqueue_init_topology - initialize CPU pods for unbound workqueues
+ *
+ * This is the third step of there-staged workqueue subsystem initialization and
+ * invoked after SMP and topology information are fully initialized. It
+ * initializes the unbound CPU pods accordingly.
+ */
+void __init workqueue_init_topology(void)
+{
+	struct workqueue_struct *wq;
+	int cpu;
+
+	init_pod_type(&wq_pod_types[WQ_AFFN_CPU], cpus_dont_share);
+	init_pod_type(&wq_pod_types[WQ_AFFN_SMT], cpus_share_smt);
+	init_pod_type(&wq_pod_types[WQ_AFFN_CACHE], cpus_share_cache);
+	init_pod_type(&wq_pod_types[WQ_AFFN_NUMA], cpus_share_numa);
+
+	mutex_lock(&wq_pool_mutex);
+
+	/*
+	 * Workqueues allocated earlier would have all CPUs sharing the default
+	 * worker pool. Explicitly call wq_update_pod() on all workqueue and CPU
+	 * combinations to apply per-pod sharing.
 	 */
-void __warn_flushing_systemwide_wq(void) { }
+	list_for_each_entry(wq, &workqueues, list) {
+		for_each_online_cpu(cpu) {
+			wq_update_pod(wq, cpu, cpu, true);
+		}
+	}
+
+	mutex_unlock(&wq_pool_mutex);
+}
+
+void __warn_flushing_systemwide_wq(void)
+{
+	pr_warn("WARNING: Flushing system-wide workqueues will be prohibited in near future.\n");
+	dump_stack();
+}
 EXPORT_SYMBOL(__warn_flushing_systemwide_wq);
+
+static int __init workqueue_unbound_cpus_setup(char *str)
+{
+	if (cpulist_parse(str, &wq_cmdline_cpumask) < 0) {
+		cpumask_clear(&wq_cmdline_cpumask);
+		pr_warn("workqueue.unbound_cpus: incorrect CPU range, using default\n");
+	}
+
+	return 1;
+}
+__setup("workqueue.unbound_cpus=", workqueue_unbound_cpus_setup);

kernel/workqueue_internal.h

@@ -48,7 +48,7 @@ struct worker {
 						/* A: runs through worker->node */
 
 	unsigned long		last_active;	/* K: last active timestamp */
-	unsigned int		flags;		/* X: flags */
+	unsigned int		flags;		/* L: flags */
 	int			id;		/* I: worker id */
 
 	/*

tools/workqueue/wq_dump.py

+#!/usr/bin/env drgn
+#
+# Copyright (C) 2023 Tejun Heo <tj@kernel.org>
+# Copyright (C) 2023 Meta Platforms, Inc. and affiliates.
+
+desc = """
+This is a drgn script to show the current workqueue configuration. For more
+info on drgn, visit https://github.com/osandov/drgn.
+
+Affinity Scopes
+===============
+
+Shows the CPUs that can be used for unbound workqueues and how they will be
+grouped by each available affinity type. For each type:
+
+  nr_pods   number of CPU pods in the affinity type
+  pod_cpus  CPUs in each pod
+  pod_node  NUMA node for memory allocation for each pod
+  cpu_pod   pod that each CPU is associated to
+
+Worker Pools
+============
+
+Lists all worker pools indexed by their ID. For each pool:
+
+  ref       number of pool_workqueue's associated with this pool
+  nice      nice value of the worker threads in the pool
+  idle      number of idle workers
+  workers   number of all workers
+  cpu       CPU the pool is associated with (per-cpu pool)
+  cpus      CPUs the workers in the pool can run on (unbound pool)
+
+Workqueue CPU -> pool
+=====================
+
+Lists all workqueues along with their type and worker pool association. For
+each workqueue:
+
+  NAME TYPE[,FLAGS] POOL_ID...
+
+  NAME      name of the workqueue
+  TYPE      percpu, unbound or ordered
+  FLAGS     S: strict affinity scope
+  POOL_ID   worker pool ID associated with each possible CPU
+"""
+
+import sys
+
+import drgn
+from drgn.helpers.linux.list import list_for_each_entry,list_empty
+from drgn.helpers.linux.percpu import per_cpu_ptr
+from drgn.helpers.linux.cpumask import for_each_cpu,for_each_possible_cpu
+from drgn.helpers.linux.idr import idr_for_each
+
+import argparse
+parser = argparse.ArgumentParser(description=desc,
+                                 formatter_class=argparse.RawTextHelpFormatter)
+args = parser.parse_args()
+
+def err(s):
+    print(s, file=sys.stderr, flush=True)
+    sys.exit(1)
+
+def cpumask_str(cpumask):
+    output = ""
+    base = 0
+    v = 0
+    for cpu in for_each_cpu(cpumask[0]):
+        while cpu - base >= 32:
+            output += f'{hex(v)} '
+            base += 32
+            v = 0
+        v |= 1 << (cpu - base)
+    if v > 0:
+        output += f'{v:08x}'
+    return output.strip()
+
+worker_pool_idr         = prog['worker_pool_idr']
+workqueues              = prog['workqueues']
+wq_unbound_cpumask      = prog['wq_unbound_cpumask']
+wq_pod_types            = prog['wq_pod_types']
+wq_affn_dfl             = prog['wq_affn_dfl']
+wq_affn_names           = prog['wq_affn_names']
+
+WQ_UNBOUND              = prog['WQ_UNBOUND']
+WQ_ORDERED              = prog['__WQ_ORDERED']
+WQ_MEM_RECLAIM          = prog['WQ_MEM_RECLAIM']
+
+WQ_AFFN_CPU             = prog['WQ_AFFN_CPU']
+WQ_AFFN_SMT             = prog['WQ_AFFN_SMT']
+WQ_AFFN_CACHE           = prog['WQ_AFFN_CACHE']
+WQ_AFFN_NUMA            = prog['WQ_AFFN_NUMA']
+WQ_AFFN_SYSTEM          = prog['WQ_AFFN_SYSTEM']
+
+print('Affinity Scopes')
+print('===============')
+
+print(f'wq_unbound_cpumask={cpumask_str(wq_unbound_cpumask)}')
+
+def print_pod_type(pt):
+    print(f'  nr_pods  {pt.nr_pods.value_()}')
+
+    print('  pod_cpus', end='')
+    for pod in range(pt.nr_pods):
+        print(f' [{pod}]={cpumask_str(pt.pod_cpus[pod])}', end='')
+    print('')
+
+    print('  pod_node', end='')
+    for pod in range(pt.nr_pods):
+        print(f' [{pod}]={pt.pod_node[pod].value_()}', end='')
+    print('')
+
+    print(f'  cpu_pod ', end='')
+    for cpu in for_each_possible_cpu(prog):
+        print(f' [{cpu}]={pt.cpu_pod[cpu].value_()}', end='')
+    print('')
+
+for affn in [WQ_AFFN_CPU, WQ_AFFN_SMT, WQ_AFFN_CACHE, WQ_AFFN_NUMA, WQ_AFFN_SYSTEM]:
+    print('')
+    print(f'{wq_affn_names[affn].string_().decode().upper()}{" (default)" if affn == wq_affn_dfl else ""}')
+    print_pod_type(wq_pod_types[affn])
+
+print('')
+print('Worker Pools')
+print('============')
+
+max_pool_id_len = 0
+max_ref_len = 0
+for pi, pool in idr_for_each(worker_pool_idr):
+    pool = drgn.Object(prog, 'struct worker_pool', address=pool)
+    max_pool_id_len = max(max_pool_id_len, len(f'{pi}'))
+    max_ref_len = max(max_ref_len, len(f'{pool.refcnt.value_()}'))
+
+for pi, pool in idr_for_each(worker_pool_idr):
+    pool = drgn.Object(prog, 'struct worker_pool', address=pool)
+    print(f'pool[{pi:0{max_pool_id_len}}] ref={pool.refcnt.value_():{max_ref_len}} nice={pool.attrs.nice.value_():3} ', end='')
+    print(f'idle/workers={pool.nr_idle.value_():3}/{pool.nr_workers.value_():3} ', end='')
+    if pool.cpu >= 0:
+        print(f'cpu={pool.cpu.value_():3}', end='')
+    else:
+        print(f'cpus={cpumask_str(pool.attrs.cpumask)}', end='')
+        print(f' pod_cpus={cpumask_str(pool.attrs.__pod_cpumask)}', end='')
+        if pool.attrs.affn_strict:
+            print(' strict', end='')
+    print('')
+
+print('')
+print('Workqueue CPU -> pool')
+print('=====================')
+
+print('[    workqueue     \     type   CPU', end='')
+for cpu in for_each_possible_cpu(prog):
+    print(f' {cpu:{max_pool_id_len}}', end='')
+print(' dfl]')
+
+for wq in list_for_each_entry('struct workqueue_struct', workqueues.address_of_(), 'list'):
+    print(f'{wq.name.string_().decode()[-24:]:24}', end='')
+    if wq.flags & WQ_UNBOUND:
+        if wq.flags & WQ_ORDERED:
+            print(' ordered   ', end='')
+        else:
+            print(' unbound', end='')
+            if wq.unbound_attrs.affn_strict:
+                print(',S ', end='')
+            else:
+                print('   ', end='')
+    else:
+        print(' percpu    ', end='')
+
+    for cpu in for_each_possible_cpu(prog):
+        pool_id = per_cpu_ptr(wq.cpu_pwq, cpu)[0].pool.id.value_()
+        field_len = max(len(str(cpu)), max_pool_id_len)
+        print(f' {pool_id:{field_len}}', end='')
+
+    if wq.flags & WQ_UNBOUND:
+        print(f' {wq.dfl_pwq.pool.id.value_():{max_pool_id_len}}', end='')
+    print('')

tools/workqueue/wq_monitor.py

@@ -20,8 +20,11 @@ https://github.com/osandov/drgn.
            and got excluded from concurrency management to avoid stalling
            other work items.
 
-  CMwake   The number of concurrency-management wake-ups while executing a
-           work item of the workqueue.
+  CMW/RPR  For per-cpu workqueues, the number of concurrency-management
+           wake-ups while executing a work item of the workqueue. For
+           unbound workqueues, the number of times a worker was repatriated
+           to its affinity scope after being migrated to an off-scope CPU by
+           the scheduler.
 
   mayday   The number of times the rescuer was requested while waiting for
            new worker creation.
@@ -65,6 +68,7 @@ PWQ_STAT_COMPLETED      = prog['PWQ_STAT_COMPLETED']	# work items completed exec
 PWQ_STAT_CPU_TIME       = prog['PWQ_STAT_CPU_TIME']     # total CPU time consumed
 PWQ_STAT_CPU_INTENSIVE  = prog['PWQ_STAT_CPU_INTENSIVE'] # wq_cpu_intensive_thresh_us violations
 PWQ_STAT_CM_WAKEUP      = prog['PWQ_STAT_CM_WAKEUP']    # concurrency-management worker wakeups
+PWQ_STAT_REPATRIATED    = prog['PWQ_STAT_REPATRIATED']  # unbound workers brought back into scope
 PWQ_STAT_MAYDAY         = prog['PWQ_STAT_MAYDAY']	# maydays to rescuer
 PWQ_STAT_RESCUED        = prog['PWQ_STAT_RESCUED']	# linked work items executed by rescuer
 PWQ_NR_STATS            = prog['PWQ_NR_STATS']
@@ -89,22 +93,25 @@ class WqStats:
                  'cpu_time'             : self.stats[PWQ_STAT_CPU_TIME],
                  'cpu_intensive'        : self.stats[PWQ_STAT_CPU_INTENSIVE],
                  'cm_wakeup'            : self.stats[PWQ_STAT_CM_WAKEUP],
+                 'repatriated'          : self.stats[PWQ_STAT_REPATRIATED],
                  'mayday'               : self.stats[PWQ_STAT_MAYDAY],
                  'rescued'              : self.stats[PWQ_STAT_RESCUED], }
 
     def table_header_str():
         return f'{"":>24} {"total":>8} {"infl":>5} {"CPUtime":>8} '\
-            f'{"CPUitsv":>7} {"CMwake":>7} {"mayday":>7} {"rescued":>7}'
+            f'{"CPUitsv":>7} {"CMW/RPR":>7} {"mayday":>7} {"rescued":>7}'
 
     def table_row_str(self):
         cpu_intensive = '-'
-        cm_wakeup = '-'
+        cmw_rpr = '-'
         mayday = '-'
         rescued = '-'
 
-        if not self.unbound:
+        if self.unbound:
+            cmw_rpr = str(self.stats[PWQ_STAT_REPATRIATED]);
+        else:
             cpu_intensive = str(self.stats[PWQ_STAT_CPU_INTENSIVE])
-            cm_wakeup = str(self.stats[PWQ_STAT_CM_WAKEUP])
+            cmw_rpr = str(self.stats[PWQ_STAT_CM_WAKEUP])
 
         if self.mem_reclaim:
             mayday = str(self.stats[PWQ_STAT_MAYDAY])
@@ -115,7 +122,7 @@ class WqStats:
               f'{max(self.stats[PWQ_STAT_STARTED] - self.stats[PWQ_STAT_COMPLETED], 0):5} ' \
               f'{self.stats[PWQ_STAT_CPU_TIME] / 1000000:8.1f} ' \
               f'{cpu_intensive:>7} ' \
-              f'{cm_wakeup:>7} ' \
+              f'{cmw_rpr:>7} ' \
               f'{mayday:>7} ' \
               f'{rescued:>7} '
         return out.rstrip(':')