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  1. 11 Jul, 2024 3 commits
    • Lai Jiangshan's avatar
      workqueue: Remove cpus_read_lock() from apply_wqattrs_lock() · 19af4575
      Lai Jiangshan authored 
      1726a171 ("workqueue: Put PWQ allocation and WQ enlistment in the same
lock C.S.") led to the following possible deadlock:

  WARNING: possible recursive locking detected
  6.10.0-rc5-00004-g1d4c6111406c #1 Not tainted
   --------------------------------------------
   swapper/0/1 is trying to acquire lock:
   c27760f4 (cpu_hotplug_lock){++++}-{0:0}, at: alloc_workqueue (kernel/workqueue.c:5152 kernel/workqueue.c:5730) 
  
   but task is already holding lock:
   c27760f4 (cpu_hotplug_lock){++++}-{0:0}, at: padata_alloc (kernel/padata.c:1007) 
   ...  
   stack backtrace:
   ...
   cpus_read_lock (include/linux/percpu-rwsem.h:53 kernel/cpu.c:488) 
   alloc_workqueue (kernel/workqueue.c:5152 kernel/workqueue.c:5730) 
   padata_alloc (kernel/padata.c:1007 (discriminator 1)) 
   pcrypt_init_padata (crypto/pcrypt.c:327 (discriminator 1)) 
   pcrypt_init (crypto/pcrypt.c:353) 
   do_one_initcall (init/main.c:1267) 
   do_initcalls (init/main.c:1328 (discriminator 1) init/main.c:1345 (discriminator 1)) 
   kernel_init_freeable (init/main.c:1364) 
   kernel_init (init/main.c:1469) 
   ret_from_fork (arch/x86/kernel/process.c:153) 
   ret_from_fork_asm (arch/x86/entry/entry_32.S:737) 
   entry_INT80_32 (arch/x86/entry/entry_32.S:944) 

This is caused by pcrypt allocating a workqueue while holding
cpus_read_lock(), so workqueue code can't do it again as that can lead to
deadlocks if down_write starts after the first down_read.

The pwq creations and installations have been reworked based on
wq_online_cpumask rather than cpu_online_mask making cpus_read_lock() is
unneeded during wqattrs changes. Fix the deadlock by removing
cpus_read_lock() from apply_wqattrs_lock().

tj: Updated changelog.
Signed-off-by: default avatarLai Jiangshan <jiangshan.ljs@antgroup.com>
Fixes: 1726a171 ("workqueue: Put PWQ allocation and WQ enlistment in the same lock C.S.")
Link: http://lkml.kernel.org/r/202407081521.83b627c1-lkp@intel.comSigned-off-by: default avatarTejun Heo <tj@kernel.org>
      19af4575
    • Lai Jiangshan's avatar
      workqueue: Simplify wq_calc_pod_cpumask() with wq_online_cpumask · fbb3d4c1
      Lai Jiangshan authored 
      Avoid relying on cpu_online_mask for wqattrs changes so that
cpus_read_lock() can be removed from apply_wqattrs_lock().

And with wq_online_cpumask, attrs->__pod_cpumask doesn't need to be
reused as a temporary storage to calculate if the pod have any online
CPUs @attrs wants since @cpu_going_down is not in the wq_online_cpumask.
Signed-off-by: default avatarLai Jiangshan <jiangshan.ljs@antgroup.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      fbb3d4c1
    • Lai Jiangshan's avatar
      workqueue: Add wq_online_cpumask · 8d84baf7
      Lai Jiangshan authored 
      The new wq_online_mask mirrors the cpu_online_mask except during
hotplugging; specifically, it differs between the hotplugging stages
of workqueue_offline_cpu() and workqueue_online_cpu(), during which
the transitioning CPU is not represented in the mask.
Signed-off-by: default avatarLai Jiangshan <jiangshan.ljs@antgroup.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      8d84baf7
  3. 05 Jul, 2024 5 commits
  5. 02 Jul, 2024 2 commits
  7. 25 Jun, 2024 2 commits
  9. 21 Jun, 2024 4 commits
  11. 19 Jun, 2024 1 commit
    • Lai Jiangshan's avatar
      workqueue: Avoid nr_active manipulation in grabbing inactive items · b56c7207
      Lai Jiangshan authored 
      Current try_to_grab_pending() activates the inactive item and
subsequently treats it as though it were a standard activated item.

This approach prevents duplicating handling logic for both active and
inactive items, yet the premature activation of an inactive item
triggers trace_workqueue_activate_work(), yielding an unintended user
space visible side effect.

And the unnecessary increment of the nr_active, which is not a simple
counter now, followed by a counteracted decrement, is inefficient and
complicates the code.

Just remove the nr_active manipulation code in grabbing inactive items.
Signed-off-by: default avatarLai Jiangshan <jiangshan.ljs@antgroup.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      b56c7207
  13. 10 Jun, 2024 1 commit
    • Julia Lawall's avatar
      workqueue: replace call_rcu by kfree_rcu for simple kmem_cache_free callback · 37c2277f
      Julia Lawall authored 
      Since SLOB was removed, it is not necessary to use call_rcu
when the callback only performs kmem_cache_free. Use
kfree_rcu() directly.

The changes were done using the following Coccinelle semantic patch.
This semantic patch is designed to ignore cases where the callback
function is used in another way.

// <smpl>
@r@
expression e;
local idexpression e2;
identifier cb,f;
position p;
@@

(
call_rcu(...,e2)
|
call_rcu(&e->f,cb@p)
)

@r1@
type T;
identifier x,r.cb;
@@

 cb(...) {
(
   kmem_cache_free(...);
|
   T x = ...;
   kmem_cache_free(...,x);
|
   T x;
   x = ...;
   kmem_cache_free(...,x);
)
 }

@s depends on r1@
position p != r.p;
identifier r.cb;
@@

 cb@p

@script:ocaml@
cb << r.cb;
p << s.p;
@@

Printf.eprintf "Other use of %s at %s:%d\n"
   cb (List.hd p).file (List.hd p).line

@depends on r1 && !s@
expression e;
identifier r.cb,f;
position r.p;
@@

- call_rcu(&e->f,cb@p)
+ kfree_rcu(e,f)

@r1a depends on !s@
type T;
identifier x,r.cb;
@@

- cb(...) {
(
-  kmem_cache_free(...);
|
-  T x = ...;
-  kmem_cache_free(...,x);
|
-  T x;
-  x = ...;
-  kmem_cache_free(...,x);
)
- }
// </smpl>
Signed-off-by: default avatarJulia Lawall <Julia.Lawall@inria.fr>
Reviewed-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Reviewed-by: default avatarVlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      37c2277f
  15. 07 Jun, 2024 1 commit
  17. 06 Jun, 2024 21 commits
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