Merge branches 'doc.2017.10.20a', 'fixes.2017.10.19a', 'stall.2017.10.09a' and 'torture.2017.10.09a' into HEAD

doc.2017.10.20a: Documentation updates.
fixes.2017.10.19a: Miscellaneous fixes.
stall.2017.10.09a: RCU CPU stall-warning updates.
torture.2017.10.09a: Torture-test updates.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

The "Write (or store) memory barriers" bullet of the "Variety of memory
barriers" section, calls out a sequential order of stores, which is
confusing since sequential ordering is not guaranteed.

This commit therefore rewords to avoid mentioning a sequence of stores
to clarify the intent.

Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@linux.vnet.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

In the "general barrier pairing with implicit control depdendency"
example, the last write by CPU 1 was meant to change variable x and not
y. The example would be pretty uninteresting if no CPU ever changes x
and the variable was initialized to zero.
Signed-off-by: Scott Tsai <scottt@scottt.tw>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

The RT build on ARM complains about non-existing ULONG_CMP_LT.
This commit therefore includes rcupdate.h into rcu_segcblist.c.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

If you add or remove calls to rcu_idle_enter(), rcu_user_enter(),
rcu_irq_exit(), rcu_irq_exit_irqson(), rcu_idle_exit(), rcu_user_exit(),
rcu_irq_enter(), rcu_irq_enter_irqson(), rcu_nmi_enter(), or
rcu_nmi_exit(), you should run a full set of tests on a kernel built
with CONFIG_RCU_EQS_DEBUG=y.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

RCU priority boosting uses rt_mutex_init_proxy_locked() to initialize an
rt_mutex structure in locked state held by some other task.  When that
other task releases it, lockdep complains (quite accurately, but a bit
uselessly) that the other task never acquired it.  This complaint can
suppress other, more helpful, lockdep complaints, and in any case it is
a false positive.

This commit therefore switches from rt_mutex_unlock() to
rt_mutex_futex_unlock(), thereby avoiding the lockdep annotations.
Of course, if lockdep ever learns about rt_mutex_init_proxy_locked(),
addtional adjustments will be required.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

This commit adjusts include files and provides definitions in preparation
for suppressing lockdep false-positive ->boost_mtx complaints.  Without
this preparation, architectures not supporting rt_mutex will get build
failures.
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Both rcutorture and locktorture currently place temporary files in /tmp,
in keeping with decades-long tradition.  However, sometimes it is useful
to specify an alternative temporary directory, for example, for space
or performance reasons.  This commit therefore causes the torture-test
scripting to use the path specified in the TMPDIR environment variable,
or to fall back to traditional /tmp if this variable is not set.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Right now, rcutorture warns if an rcu_torture_writer() kthread stalls,
but this warning is not always all that helpful.  This commit therefore
makes the first such warning include a stack dump.

This in turn requires that sched_show_task() be exported to GPL modules,
so this commit makes that change as well.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

When rcutorture sees the rcutorture.stall_cpu kernel boot parameter,
it loops with preemption disabled, which does in fact normally
generate an RCU CPU stall warning message.  However, there are test
scenarios that need the stalling CPU to have interrupts disabled.
This commit therefore adds an rcutorture.stall_cpu_irqsoff kernel
boot parameter that causes the stalling CPU to disable interrupts.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Currently, RCU emits Suppress RCU CPU stall warnings during its
automatically initiated ftrace_dump() calls after detecting an error
condition, which can result in excessively excessive console output
and lost trace events.  This commit therefore suppresses RCU CPU stall
warnings across any of these ftrace_dump() calls.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Currently, RCU allows tracing to continue when it automatically does
ftrace_dump() after detecting an error condition, which can result in
excessively large traces and lost trace events.  This commit therefore
does a tracing_off() before any of these ftrace_dump() calls.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

One common question upon seeing an RCU CPU stall warning is "did
the stalled CPUs have interrupts disabled?"  However, the current
stall warnings are silent on this point.  This commit therefore
uses irq_work to check whether stalled CPUs still respond to IPIs,
and flags this state in the RCU CPU stall warning console messages.
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

There is some confusion as to which of cond_resched() or
cond_resched_rcu_qs() should be added to long in-kernel loops.
This commit therefore eliminates the decision by adding RCU quiescent
states to cond_resched().  This commit also simplifies the code that
used to interact with cond_resched_rcu_qs(), and that now interacts with
cond_resched(), to reduce its overhead.  This reduction is necessary to
allow the heavier-weight cond_resched_rcu_qs() mechanism to be invoked
everywhere that cond_resched() is invoked.

Part of that reduction in overhead converts the jiffies_till_sched_qs
kernel parameter to read-only at runtime, thus eliminating the need for
bounds checking.
Reported-by: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
[ paulmck: Keep PREEMPT=n cond_resched a no-op, per Peter Zijlstra. ]

The current implementation of synchronize_sched_expedited() incorrectly
assumes that resched_cpu() is unconditional, which it is not.  This means
that synchronize_sched_expedited() can hang when resched_cpu()'s trylock
fails as follows (analysis by Neeraj Upadhyay):

o	CPU1 is waiting for expedited wait to complete:

	sync_rcu_exp_select_cpus
	     rdp->exp_dynticks_snap & 0x1   // returns 1 for CPU5
	     IPI sent to CPU5

	synchronize_sched_expedited_wait
		 ret = swait_event_timeout(rsp->expedited_wq,
					   sync_rcu_preempt_exp_done(rnp_root),
					   jiffies_stall);

	expmask = 0x20, CPU 5 in idle path (in cpuidle_enter())

o	CPU5 handles IPI and fails to acquire rq lock.

	Handles IPI
	     sync_sched_exp_handler
		 resched_cpu
		     returns while failing to try lock acquire rq->lock
		 need_resched is not set

o	CPU5 calls  rcu_idle_enter() and as need_resched is not set, goes to
	idle (schedule() is not called).

o	CPU 1 reports RCU stall.

Given that resched_cpu() is now used only by RCU, this commit fixes the
assumption by making resched_cpu() unconditional.
Reported-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Suggested-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org

Commit 47885016 ("irq_work: Implement remote queueing") provides
irq_work_on_queue() only for SMP builds.  However, providing it simplifies
code that submits irq_work to lists of CPUs, eliminating the !SMP special
cases.  This commit therefore maps irq_work_on_queue() to irq_work_on()
in !SMP builds, but validating the specified CPU.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Currently the call_rcu_tasks() kthread is created upon first
invocation of call_rcu_tasks().  This has the advantage of avoiding
creation if there are never any invocations of call_rcu_tasks() and of
synchronize_rcu_tasks(), but it requires an unreliable heuristic to
determine when it is safe to create the kthread.  For example, it is
not safe to create the kthread when call_rcu_tasks() is invoked with
a spinlock held, but there is no good way to detect this in !PREEMPT
kernels.

This commit therefore creates this kthread unconditionally at
core_initcall() time.  If you don't want this kthread created, then
build with CONFIG_TASKS_RCU=n.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

The pending-callbacks check in rcu_prepare_for_idle() is backwards.
It should accelerate if there are pending callbacks, but the check
rather uselessly accelerates only if there are no callbacks.  This commit
therefore inverts this check.

Fixes: 15fecf89 ("srcu: Abstract multi-tail callback list handling")
Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: <stable@vger.kernel.org> # 4.12.x

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

The current version of memory-barriers.txt misuses the term "transitive",
so this commit replaces it with multi-copy atomic, also adding a
definition of this term.
Reported-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

The RCU CPU stall warnings have morphed significantly since the last
update, so this commit brings the documentation up to date.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

If a fast system has a worst-case grace-period duration of (say) ten
seconds, then running the same workload on a system ten times as slow
will get you an RCU CPU stall warning given default stall-warning
timeout settings.  This commit therefore adds this possibility to
stallwarn.txt.
Reported-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

If a periodic interrupt's handler takes longer to execute than the period
between successive interrupts, RCU's kthreads and softirq handlers can
be prevented from executing, resulting in otherwise inexplicable RCU
CPU stall warnings.  This commit therefore calls out this possibility
in Documentation/RCU/stallwarn.txt.
Reported-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

This commit provides text and diagrams showing how Tree RCU implements
its grace-period memory ordering guarantees.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>

Pull SCSI fixes from James Bottomley:

 - a couple of serious fixes: use after free and blacklist for WRITE
   SAME

 - one error leg fix: write_pending failure

 - one user experience problem: do not override max_sectors_kb

 - one minor unused function removal

* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
  scsi: ibmvscsis: Fix write_pending failure path
  scsi: libiscsi: Remove iscsi_destroy_session
  scsi: libiscsi: Fix use-after-free race during iscsi_session_teardown
  scsi: sd: Do not override max_sectors_kb sysfs setting
  scsi: sd: Implement blacklist option for WRITE SAME w/ UNMAP

Pull i2c fixes from Wolfram Sang:
 "I2C has three driver fixes for the newly introduced drivers and one ID
  addition for the i801 driver"

* 'i2c/for-current-4.14' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux:
  i2c: i2c-stm32f7: make structure stm32f7_setup static const
  i2c: ensure termination of *_device_id tables
  i2c: i801: Add support for Intel Cedar Fork
  i2c: stm32f7: fix setup structure

Pull MMC fixes from Ulf Hansson:
 "MMC core:

   - Fix driver strength selection when selecting hs400es

   - Delete bounce buffer handling:

     This change fixes a problem related to how bounce buffers are being
     allocated. However, instead of trying to fix that, let's just
     remove the mmc bounce buffer code altogether, as it has practically
     no use.

  MMC host:

   - meson-gx: A couple of fixes related to clock/phase/tuning

   - sdhci-xenon: Fix clock resource by adding an optional bus clock"

* tag 'mmc-v4.14-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/ulfh/mmc:
  mmc: sdhci-xenon: Fix clock resource by adding an optional bus clock
  mmc: meson-gx: include tx phase in the tuning process
  mmc: meson-gx: fix rx phase reset
  mmc: meson-gx: make sure the clock is rounded down
  mmc: Delete bounce buffer handling
  mmc: core: add driver strength selection when selecting hs400es

Merge tag 'hwmon-for-linus-v4.14-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/groeck/linux-staging

Pull hwmon fix from Guenter Roeck:
 "Fix up error path in xgene driver"

* tag 'hwmon-for-linus-v4.14-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/groeck/linux-staging:
  hwmon: (xgene) Fix up error handling path mixup in 'xgene_hwmon_probe()'

Pull clk fixes from Stephen Boyd:

 - build fix to export the clk_bulk_prepare() symbol

 - suspend fix for Samsung Exynos SoCs where we need to keep clks on
   across suspend

 - two critical clk markings for clks that shouldn't ever turn off on
   Rockchip SoCs

 - a fix for a copy-paste mistake on Rockchip rk3128 causing some clks
   to touch the same bit and trample over one another

* tag 'clk-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/clk/linux:
  clk: samsung: exynos4: Enable VPLL and EPLL clocks for suspend/resume cycle
  clk: Export clk_bulk_prepare()
  clk: rockchip: add sclk_timer5 as critical clock on rk3128
  clk: rockchip: fix up rk3128 pvtm and mipi_24m gate regs error
  clk: rockchip: add pclk_pmu as critical clock on rk3128

Pull ARC udpates from Vineet Gupta:

 - updates for various platforms

 - boot log updates for upcoming HS48 family of cores (dual issue)

* tag 'arc-4.14-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc:
  ARC: [plat-hsdk]: Add reset controller node to manage ethernet reset
  ARC: [plat-hsdk]: Temporary fix to set CPU frequency to 1GHz
  ARC: fix allnoconfig build warning
  ARCv2: boot log: identify HS48 cores (dual issue)
  ARC: boot log: decontaminate ARCv2 ISA_CONFIG register
  arc: remove redundant UTS_MACHINE define in arch/arc/Makefile
  ARC: [plat-eznps] Update platform maintainer as Noam left
  ARC: [plat-hsdk] use actual clk driver to manage cpu clk
  ARC: [*defconfig] Reenable soft lock-up detector
  ARC: [plat-axs10x] sdio: Temporary fix of sdio ciu frequency
  ARC: [plat-hsdk] sdio: Temporary fix of sdio ciu frequency
  ARC: [plat-axs103] Add temporary quirk to reset ethernet IP

Pull xfs fixes from Darrick Wong:

 - fix a race between overlapping copy on write aio

 - fix cow fork swapping when we defragment reflinked files

* tag 'xfs-4.14-fixes-4' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux:
  xfs: handle racy AIO in xfs_reflink_end_cow
  xfs: always swap the cow forks when swapping extents

Pull block fixes from Jens Axboe:
 "A collection of fixes for this series. This contains:

   - NVMe pull request from Christoph, one uuid attribute fix, and one
     fix for the controller memory buffer address for remapped BARs.

   - use-after-free fix for bsg, from Benjamin Block.

   - bcache race/use-after-free fix for a list traversal, fixing a
     regression in this merge window. From Coly Li.

   - null_blk change configfs dependency change from a 'depends' to a
     'select'. This is a change from this merge window as well. From me.

   - nbd signal fix from Josef, fixing a regression introduced with the
     status code changes.

   - nbd MAINTAINERS mailing list entry update.

   - blk-throttle stall fix from Joseph Qi.

   - blk-mq-debugfs fix from Omar, fixing an issue where we don't
     register the IO scheduler debugfs directory, if the driver is
     loaded with it. Only shows up if you switch through the sysfs
     interface"

* 'for-linus' of git://git.kernel.dk/linux-block:
  bsg-lib: fix use-after-free under memory-pressure
  nvme-pci: Use PCI bus address for data/queues in CMB
  blk-mq-debugfs: fix device sched directory for default scheduler
  null_blk: change configfs dependency to select
  blk-throttle: fix possible io stall when upgrade to max
  MAINTAINERS: update list for NBD
  nbd: fix -ERESTARTSYS handling
  nvme: fix visibility of "uuid" ns attribute
  bcache: use llist_for_each_entry_safe() in __closure_wake_up()

Pull PCI fixes from Bjorn Helgaas:
 "Fix legacy IDE probe issues exposed by recent PCI core IRQ mapping
  changes (Bartlomiej Zolnierkiewicz, Lorenzo Pieralisi)"

* tag 'pci-v4.14-fixes-4' of git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci:
  ide: fix IRQ assignment for PCI bus order probing
  ide: pci: free PCI BARs on initialization failure
  ide: free hwif->portdev on hwif_init() failure

Pull arm64 fixes from Catalin Marinas:

 - Bring initialisation of user space undefined instruction handling
   early (core_initcall) since late_initcall() happens after modprobe in
   initramfs is invoked. Similar fix for fpsimd initialisation

 - Increase the kernel stack when KASAN is enabled

 - Bring the PCI ACS enabling earlier via the
   iort_init_platform_devices()

 - Fix misleading data abort address printing (decimal vs hex)

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  arm64: Ensure fpsimd support is ready before userspace is active
  arm64: Ensure the instruction emulation is ready for userspace
  arm64: Use larger stacks when KASAN is selected
  ACPI/IORT: Fix PCI ACS enablement
  arm64: fix misleading data abort decoding

Pull KVM fixes from Radim Krčmář:

 - fix PPC XIVE interrupt delivery

 - fix x86 RCU breakage from asynchronous page faults when built without
   PREEMPT_COUNT

 - fix x86 build with -frecord-gcc-switches

 - fix x86 build without X86_LOCAL_APIC

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
  KVM: add X86_LOCAL_APIC dependency
  x86/kvm: Move kvm_fastop_exception to .fixup section
  kvm/x86: Avoid async PF preempting the kernel incorrectly
  KVM: PPC: Book3S: Fix server always zero from kvmppc_xive_get_xive()

Pull rdma fixes from Doug Ledford:
 "This is a pretty small pull request. Only 6 patches in total. There
  are no outstanding -rc patches on the mailing list after this pull
  request, so only if some new issues are discovered in the remainder of
  the rc cycles will you hear from me again.

  Summary:
   - a fix for iwpm netlink usage
   - a fix for error unwinding in mlx5
   - two fixes to vlan handling in qedr
   - a couple small i40iw fixes"

* tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dledford/rdma:
  i40iw: Fix port number for query QP
  i40iw: Add missing memory barriers
  RDMA/qedr: Parse vlan priority as sl
  RDMA/qedr: Parse VLAN ID correctly and ignore the value of zero
  IB/mlx5: Fix label order in error path handling
  RDMA/iwpm: Properly mark end of NL messages

Pull btrfs fixes from David Sterba:
 "Two more fixes for bugs introduced in 4.13.

  The sector_t problem with 32bit architecture and !LBDAF config seems
  serious but the number of affected deployments is hopefully low.

  The clashing status bits could lead to a confusing in-memory state of
  the whole-filesystem operations if used with the quota override sysfs
  knob"

* 'for-4.14-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  Btrfs: fix overlap of fs_info::flags values
  btrfs: avoid overflow when sector_t is 32 bit

Pull ceph fixes from Ilya Dryomov:
 "Two fixups for CephFS snapshot-handling patches in -rc1"

* tag 'ceph-for-4.14-rc4' of git://github.com/ceph/ceph-client:
  ceph: fix __choose_mds() for LSSNAP request
  ceph: properly queue cap snap for newly created snap realm