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Merge branch 'for-4.15' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 
Pull workqueue updates from Tejun Heo:
 "There was a commit to make unbound kworkers respect cpu isolation but
  it conflicted with the restructuring of cpu isolation and got
  reverted, so the only thing left is the trivial comment fix.

  Will retry the cpu isolation change after this merge window"

* 'for-4.15' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
  workqueue: Fix comment for unbound workqueue's attrbutes
  Revert "workqueue: respect isolated cpus when queueing an unbound work"
  workqueue: respect isolated cpus when queueing an unbound work

Linus Torvalds   commited 2017-11-15 14:15:21 -08:00
0be500363c
Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 
Pull timer updates from Thomas Gleixner:
 "Yet another big pile of changes:

   - More year 2038 work from Arnd slowly reaching the point where we
     need to think about the syscalls themself.

   - A new timer function which allows to conditionally (re)arm a timer
     only when it's either not running or the new expiry time is sooner
     than the armed expiry time. This allows to use a single timer for
     multiple timeout requirements w/o caring about the first expiry
     time at the call site.

   - A new NMI safe accessor to clock real time for the printk timestamp
     work. Can be used by tracing, perf as well if required.

   - A large number of timer setup conversions from Kees which got
     collected here because either maintainers requested so or they
     simply got ignored. As Kees pointed out already there are a few
     trivial merge conflicts and some redundant commits which was
     unavoidable due to the size of this conversion effort.

   - Avoid a redundant iteration in the timer wheel softirq processing.

   - Provide a mechanism to treat RTC implementations depending on their
     hardware properties, i.e. don't inflict the write at the 0.5
     seconds boundary which originates from the PC CMOS RTC to all RTCs.
     No functional change as drivers need to be updated separately.

   - The usual small updates to core code clocksource drivers. Nothing
     really exciting"

* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (111 commits)
  timers: Add a function to start/reduce a timer
  pstore: Use ktime_get_real_fast_ns() instead of __getnstimeofday()
  timer: Prepare to change all DEFINE_TIMER() callbacks
  netfilter: ipvs: Convert timers to use timer_setup()
  scsi: qla2xxx: Convert timers to use timer_setup()
  block/aoe: discover_timer: Convert timers to use timer_setup()
  ide: Convert timers to use timer_setup()
  drbd: Convert timers to use timer_setup()
  mailbox: Convert timers to use timer_setup()
  crypto: Convert timers to use timer_setup()
  drivers/pcmcia: omap1: Fix error in automated timer conversion
  ARM: footbridge: Fix typo in timer conversion
  drivers/sgi-xp: Convert timers to use timer_setup()
  drivers/pcmcia: Convert timers to use timer_setup()
  drivers/memstick: Convert timers to use timer_setup()
  drivers/macintosh: Convert timers to use timer_setup()
  hwrng/xgene-rng: Convert timers to use timer_setup()
  auxdisplay: Convert timers to use timer_setup()
  sparc/led: Convert timers to use timer_setup()
  mips: ip22/32: Convert timers to use timer_setup()
  ...

Linus Torvalds   commited 2017-11-13 17:56:58 -08:00
2bcc673101
workqueue: Use lockdep to assert IRQs are disabled/enabled 
Use lockdep to check that IRQs are enabled or disabled as expected. This
way the sanity check only shows overhead when concurrency correctness
debug code is enabled.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: David S . Miller <davem@davemloft.net>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1509980490-4285-4-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Frederic Weisbecker   authored and   Ingo Molnar   commited 2017-11-08 11:13:48 +01:00
8e8eb73075
Merge branch 'linus' into locking/core, to resolve conflicts 
Conflicts:
	include/linux/compiler-clang.h
	include/linux/compiler-gcc.h
	include/linux/compiler-intel.h
	include/uapi/linux/stddef.h

Signed-off-by: Ingo Molnar <mingo@kernel.org>

Ingo Molnar   commited 2017-11-07 10:32:44 +01:00
8c5db92a70
workqueue: Fix comment for unbound workqueue's attrbutes 
Signed-off-by: Wang Long <wanglong19@meituan.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

Wang Long   authored and   Tejun Heo   commited 2017-11-06 07:04:47 -08:00
9a19b46386
Revert "workqueue: respect isolated cpus when queueing an unbound work" 
This reverts commit b5149873a0.

It conflicts with the following isolcpus change from the sched branch.

 edb9382175 ("sched/isolation: Move isolcpus= handling to the housekeeping code")

Let's revert for now.

Signed-off-by: Tejun Heo <tj@kernel.org>

Tejun Heo   commited 2017-11-03 07:02:15 -07:00
edbfd9112f
workqueue: Remove now redundant lock acquisitions wrt. workqueue flushes 
The workqueue code added manual lock acquisition annotations to catch
deadlocks.

After lockdepcrossrelease was introduced, some of those became redundant,
since wait_for_completion() already does the acquisition and tracking.

Remove the duplicate annotations.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: amir73il@gmail.com
Cc: axboe@kernel.dk
Cc: darrick.wong@oracle.com
Cc: david@fromorbit.com
Cc: hch@infradead.org
Cc: idryomov@gmail.com
Cc: johan@kernel.org
Cc: johannes.berg@intel.com
Cc: kernel-team@lge.com
Cc: linux-block@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: linux-xfs@vger.kernel.org
Cc: oleg@redhat.com
Cc: tj@kernel.org
Link: http://lkml.kernel.org/r/1508921765-15396-9-git-send-email-byungchul.park@lge.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Byungchul Park   authored and   Ingo Molnar   commited 2017-10-25 12:19:03 +02:00
fd1a5b04df
locking/atomics, workqueue: Convert ACCESS_ONCE() to READ_ONCE()/WRITE_ONCE() 
For several reasons, it is desirable to use {READ,WRITE}_ONCE() in
preference to ACCESS_ONCE(), and new code is expected to use one of the
former. So far, there's been no reason to change most existing uses of
ACCESS_ONCE(), as these aren't currently harmful.

However, for some features it is necessary to instrument reads and
writes separately, which is not possible with ACCESS_ONCE(). This
distinction is critical to correct operation.

It's possible to transform the bulk of kernel code using the Coccinelle
script below. However, this doesn't handle comments, leaving references
to ACCESS_ONCE() instances which have been removed. As a preparatory
step, this patch converts the workqueue code and comments to use
{READ,WRITE}_ONCE() consistently.

----
virtual patch

@ depends on patch @
expression E1, E2;
@@

- ACCESS_ONCE(E1) = E2
+ WRITE_ONCE(E1, E2)

@ depends on patch @
expression E;
@@

- ACCESS_ONCE(E)
+ READ_ONCE(E)
----

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: davem@davemloft.net
Cc: linux-arch@vger.kernel.org
Cc: mpe@ellerman.id.au
Cc: shuah@kernel.org
Cc: snitzer@redhat.com
Cc: thor.thayer@linux.intel.com
Cc: viro@zeniv.linux.org.uk
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/1508792849-3115-12-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Mark Rutland   authored and   Ingo Molnar   commited 2017-10-25 11:01:03 +02:00
c95491ed6d
workqueue: respect isolated cpus when queueing an unbound work 
Initialize wq_unbound_cpumask to exclude cpus that were isolated by
the cmdline's isolcpus parameter.

Signed-off-by: Tal Shorer <tal.shorer@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

Tal Shorer   authored and   Tejun Heo   commited 2017-10-21 09:32:15 -07:00
b5149873a0
workqueue: Convert timers to use timer_setup() (part 2) 
In preparation for unconditionally passing the struct timer_list pointer
to all timer callbacks, switch to using the new timer_setup() and
from_timer() to pass the timer pointer explicitly. (The prior workqueue
patch missed a few timers.)

Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Link: https://lkml.kernel.org/r/20171016225825.GA99101@beast
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Kees Cook   authored and   Thomas Gleixner   commited 2017-10-18 17:04:25 +02:00
32a6c7233c
workqueue: replace pool->manager_arb mutex with a flag 
Josef reported a HARDIRQ-safe -> HARDIRQ-unsafe lock order detected by
lockdep:

 [ 1270.472259] WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected
 [ 1270.472783] 4.14.0-rc1-xfstests-12888-g76833e8 #110 Not tainted
 [ 1270.473240] -----------------------------------------------------
 [ 1270.473710] kworker/u5:2/5157 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
 [ 1270.474239]  (&(&lock->wait_lock)->rlock){+.+.}, at: [<ffffffff8da253d2>] __mutex_unlock_slowpath+0xa2/0x280
 [ 1270.474994]
 [ 1270.474994] and this task is already holding:
 [ 1270.475440]  (&pool->lock/1){-.-.}, at: [<ffffffff8d2992f6>] worker_thread+0x366/0x3c0
 [ 1270.476046] which would create a new lock dependency:
 [ 1270.476436]  (&pool->lock/1){-.-.} -> (&(&lock->wait_lock)->rlock){+.+.}
 [ 1270.476949]
 [ 1270.476949] but this new dependency connects a HARDIRQ-irq-safe lock:
 [ 1270.477553]  (&pool->lock/1){-.-.}
 ...
 [ 1270.488900] to a HARDIRQ-irq-unsafe lock:
 [ 1270.489327]  (&(&lock->wait_lock)->rlock){+.+.}
 ...
 [ 1270.494735]  Possible interrupt unsafe locking scenario:
 [ 1270.494735]
 [ 1270.495250]        CPU0                    CPU1
 [ 1270.495600]        ----                    ----
 [ 1270.495947]   lock(&(&lock->wait_lock)->rlock);
 [ 1270.496295]                                local_irq_disable();
 [ 1270.496753]                                lock(&pool->lock/1);
 [ 1270.497205]                                lock(&(&lock->wait_lock)->rlock);
 [ 1270.497744]   <Interrupt>
 [ 1270.497948]     lock(&pool->lock/1);

, which will cause a irq inversion deadlock if the above lock scenario
happens.

The root cause of this safe -> unsafe lock order is the
mutex_unlock(pool->manager_arb) in manage_workers() with pool->lock
held.

Unlocking mutex while holding an irq spinlock was never safe and this
problem has been around forever but it never got noticed because the
only time the mutex is usually trylocked while holding irqlock making
actual failures very unlikely and lockdep annotation missed the
condition until the recent b9c16a0e1f ("locking/mutex: Fix
lockdep_assert_held() fail").

Using mutex for pool->manager_arb has always been a bit of stretch.
It primarily is an mechanism to arbitrate managership between workers
which can easily be done with a pool flag.  The only reason it became
a mutex is that pool destruction path wants to exclude parallel
managing operations.

This patch replaces the mutex with a new pool flag POOL_MANAGER_ACTIVE
and make the destruction path wait for the current manager on a wait
queue.

v2: Drop unnecessary flag clearing before pool destruction as
    suggested by Boqun.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: stable@vger.kernel.org

Tejun Heo   commited 2017-10-10 07:13:57 -07:00
692b48258d
workqueue: Convert callback to use from_timer() 
In preparation for unconditionally passing the struct timer_list pointer
to all timer callbacks, switch workqueue to use from_timer() and pass the
timer pointer explicitly.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mips@linux-mips.org
Cc: Petr Mladek <pmladek@suse.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Sebastian Reichel <sre@kernel.org>
Cc: Kalle Valo <kvalo@qca.qualcomm.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: linux1394-devel@lists.sourceforge.net
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: linux-s390@vger.kernel.org
Cc: linux-wireless@vger.kernel.org
Cc: "James E.J. Bottomley" <jejb@linux.vnet.ibm.com>
Cc: Wim Van Sebroeck <wim@iguana.be>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Ursula Braun <ubraun@linux.vnet.ibm.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Harish Patil <harish.patil@cavium.com>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Manish Chopra <manish.chopra@cavium.com>
Cc: Len Brown <len.brown@intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: linux-pm@vger.kernel.org
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Julian Wiedmann <jwi@linux.vnet.ibm.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Mark Gross <mark.gross@intel.com>
Cc: linux-watchdog@vger.kernel.org
Cc: linux-scsi@vger.kernel.org
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Stefan Richter <stefanr@s5r6.in-berlin.de>
Cc: Michael Reed <mdr@sgi.com>
Cc: netdev@vger.kernel.org
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Link: https://lkml.kernel.org/r/1507159627-127660-14-git-send-email-keescook@chromium.org

Kees Cook   authored and   Thomas Gleixner   commited 2017-10-05 15:01:22 +02:00
8c20feb606
timer: Remove users of TIMER_DEFERRED_INITIALIZER 
This removes uses of TIMER_DEFERRED_INITIALIZER and chooses a location
to call timer_setup() from before add_timer() or mod_timer() is called.
Adjusts callbacks to use from_timer() as needed.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mips@linux-mips.org
Cc: Petr Mladek <pmladek@suse.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Sebastian Reichel <sre@kernel.org>
Cc: Kalle Valo <kvalo@qca.qualcomm.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: linux1394-devel@lists.sourceforge.net
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: linux-s390@vger.kernel.org
Cc: linux-wireless@vger.kernel.org
Cc: "James E.J. Bottomley" <jejb@linux.vnet.ibm.com>
Cc: Wim Van Sebroeck <wim@iguana.be>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Ursula Braun <ubraun@linux.vnet.ibm.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Harish Patil <harish.patil@cavium.com>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Manish Chopra <manish.chopra@cavium.com>
Cc: Len Brown <len.brown@intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: linux-pm@vger.kernel.org
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Julian Wiedmann <jwi@linux.vnet.ibm.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Mark Gross <mark.gross@intel.com>
Cc: linux-watchdog@vger.kernel.org
Cc: linux-scsi@vger.kernel.org
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Stefan Richter <stefanr@s5r6.in-berlin.de>
Cc: Michael Reed <mdr@sgi.com>
Cc: netdev@vger.kernel.org
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Link: https://lkml.kernel.org/r/1507159627-127660-7-git-send-email-keescook@chromium.org

Kees Cook   authored and   Thomas Gleixner   commited 2017-10-05 15:01:18 +02:00
5cd79d6abd
Merge branch 'for-4.14' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 
Pull workqueue updates from Tejun Heo:
 "Nothing major. I introduced a flag collsion bug during v4.13 cycle
  which is fixed in this pull request. Fortunately, the flag is for
  debugging / verification and the bug isn't critical"

* 'for-4.14' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
  workqueue: Fix flag collision
  workqueue: Use TASK_IDLE
  workqueue: fix path to documentation
  workqueue: doc change for ST behavior on NUMA systems

Linus Torvalds   commited 2017-09-06 21:59:31 -07:00
9954d4892a
Merge branch 'for-4.13-fixes' into for-4.14
Tejun Heo   commited 2017-09-05 06:33:41 -07:00
058fc47ee2
locking/lockdep: Untangle xhlock history save/restore from task independence 
Where XHLOCK_{SOFT,HARD} are save/restore points in the xhlocks[] to
ensure the temporal IRQ events don't interact with task state, the
XHLOCK_PROC is a fundament different beast that just happens to share
the interface.

The purpose of XHLOCK_PROC is to annotate independent execution inside
one task. For example workqueues, each work should appear to run in its
own 'pristine' 'task'.

Remove XHLOCK_PROC in favour of its own interface to avoid confusion.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: boqun.feng@gmail.com
Cc: david@fromorbit.com
Cc: johannes@sipsolutions.net
Cc: kernel-team@lge.com
Cc: oleg@redhat.com
Cc: tj@kernel.org
Link: http://lkml.kernel.org/r/20170829085939.ggmb6xiohw67micb@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Peter Zijlstra   authored and   Ingo Molnar   commited 2017-08-29 15:14:38 +02:00
f52be57080
locking/lockdep: Fix workqueue crossrelease annotation 
The new completion/crossrelease annotations interact unfavourable with
the extant flush_work()/flush_workqueue() annotations.

The problem is that when a single work class does:

  wait_for_completion(&C)

and

  complete(&C)

in different executions, we'll build dependencies like:

  lock_map_acquire(W)
  complete_acquire(C)

and

  lock_map_acquire(W)
  complete_release(C)

which results in the dependency chain: W->C->W, which lockdep thinks
spells deadlock, even though there is no deadlock potential since
works are ran concurrently.

One possibility would be to change the work 'lock' to recursive-read,
but that would mean hitting a lockdep limitation on recursive locks.
Also, unconditinoally switching to recursive-read here would fail to
detect the actual deadlock on single-threaded workqueues, which do
have a problem with this.

For now, forcefully disregard these locks for crossrelease.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: boqun.feng@gmail.com
Cc: byungchul.park@lge.com
Cc: david@fromorbit.com
Cc: johannes@sipsolutions.net
Cc: oleg@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Peter Zijlstra   authored and   Ingo Molnar   commited 2017-08-25 11:06:33 +02:00
e6f3faa734
workqueue/lockdep: 'Fix' flush_work() annotation 
The flush_work() annotation as introduced by commit:

  e159489baa ("workqueue: relax lockdep annotation on flush_work()")

hits on the lockdep problem with recursive read locks.

The situation as described is:

Work W1:                Work W2:        Task:

ARR(Q)                  ARR(Q)		flush_workqueue(Q)
A(W1)                   A(W2)             A(Q)
  flush_work(W2)			  R(Q)
    A(W2)
    R(W2)
    if (special)
      A(Q)
    else
      ARR(Q)
    R(Q)

where: A - acquire, ARR - acquire-read-recursive, R - release.

Where under 'special' conditions we want to trigger a lock recursion
deadlock, but otherwise allow the flush_work(). The allowing is done
by using recursive read locks (ARR), but lockdep is broken for
recursive stuff.

However, there appears to be no need to acquire the lock if we're not
'special', so if we remove the 'else' clause things become much
simpler and no longer need the recursion thing at all.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: boqun.feng@gmail.com
Cc: byungchul.park@lge.com
Cc: david@fromorbit.com
Cc: johannes@sipsolutions.net
Cc: oleg@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Peter Zijlstra   authored and   Ingo Molnar   commited 2017-08-25 11:06:32 +02:00
a1d14934ea
workqueue: Use TASK_IDLE 
Workqueues don't use signals, it (ab)uses TASK_INTERRUPTIBLE to avoid
increasing the loadavg numbers. We've 'recently' introduced TASK_IDLE
for this case:

  80ed87c8a9 ("sched/wait: Introduce TASK_NOLOAD and TASK_IDLE")

use it.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Tejun Heo <tj@kernel.org>

Peter Zijlstra   authored and   Tejun Heo   commited 2017-08-23 06:30:35 -07:00
c5a94a618e
locking/lockdep: Explicitly initialize wq_barrier::done::map 
With the new lockdep crossrelease feature, which checks completions usage,
a false positive is reported in the workqueue code:

> Worker A : acquired of wfc.work -> wait for cpu_hotplug_lock to be released
> Task   B : acquired of cpu_hotplug_lock -> wait for lock#3 to be released
> Task   C : acquired of lock#3 -> wait for completion of barr->done
> (Task C is in lru_add_drain_all_cpuslocked())
> Worker D : wait for wfc.work to be released -> will complete barr->done

Such a dead lock can not happen because Task C's barr->done and Worker D's
barr->done can not be the same instance.

The reason of this false positive is we initialize all wq_barrier::done
at insert_wq_barrier() via init_completion(), which makes them belong to
the same lock class, therefore, impossible circles are reported.

To fix this, explicitly initialize the lockdep map for wq_barrier::done
in insert_wq_barrier(), so that the lock class key of wq_barrier::done
is a subkey of the corresponding work_struct, as a result we won't build
a dependency between a wq_barrier with a unrelated work, and we can
differ wq barriers based on the related works, so the false positive
above is avoided.

Also define the empty lockdep_init_map_crosslock() for !CROSSRELEASE
to make the code simple and away from unnecessary #ifdefs.

Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170817094622.12915-1-boqun.feng@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Boqun Feng   authored and   Ingo Molnar   commited 2017-08-17 12:12:33 +02:00
52fa5bc5cb
locking/lockdep: Implement the 'crossrelease' feature 
Lockdep is a runtime locking correctness validator that detects and
reports a deadlock or its possibility by checking dependencies between
locks. It's useful since it does not report just an actual deadlock but
also the possibility of a deadlock that has not actually happened yet.
That enables problems to be fixed before they affect real systems.

However, this facility is only applicable to typical locks, such as
spinlocks and mutexes, which are normally released within the context in
which they were acquired. However, synchronization primitives like page
locks or completions, which are allowed to be released in any context,
also create dependencies and can cause a deadlock.

So lockdep should track these locks to do a better job. The 'crossrelease'
implementation makes these primitives also be tracked.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: akpm@linux-foundation.org
Cc: boqun.feng@gmail.com
Cc: kernel-team@lge.com
Cc: kirill@shutemov.name
Cc: npiggin@gmail.com
Cc: walken@google.com
Cc: willy@infradead.org
Link: http://lkml.kernel.org/r/1502089981-21272-6-git-send-email-byungchul.park@lge.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Byungchul Park   authored and   Ingo Molnar   commited 2017-08-10 12:29:07 +02:00
b09be676e0
workqueue: fix path to documentation 
Signed-off-by: Benjamin Peterson <bp@benjamin.pe>
Signed-off-by: Tejun Heo <tj@kernel.org>

Benjamin Peterson   authored and   Tejun Heo   commited 2017-08-07 08:03:24 -07:00
9a2614916a
workqueue: Work around edge cases for calc of pool's cpumask 
There is an underlying assumption/trade-off in many layers of the Linux
system that CPU <-> node mapping is static.  This is despite the presence
of features like NUMA and 'hotplug' that support the dynamic addition/
removal of fundamental system resources like CPUs and memory.  PowerPC
systems, however, do provide extensive features for the dynamic change
of resources available to a system.

Currently, there is little or no synchronization protection around the
updating of the CPU <-> node mapping, and the export/update of this
information for other layers / modules.  In systems which can change
this mapping during 'hotplug', like PowerPC, the information is changing
underneath all layers that might reference it.

This patch attempts to ensure that a valid, usable cpumask attribute
is used by the workqueue infrastructure when setting up new resource
pools.  It prevents a crash that has been observed when an 'empty'
cpumask is passed along to the worker/task scheduling code.  It is
intended as a temporary workaround until a more fundamental review and
correction of the issue can be done.

[With additions to the patch provided by Tejun Hao <tj@kernel.org>]

Signed-off-by: Michael Bringmann <mwb@linux.vnet.ibm.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

Michael Bringmann   authored and   Tejun Heo   commited 2017-07-28 11:05:52 -04:00
1ad0f0a7aa
workqueue: implicit ordered attribute should be overridable 
5c0338c687 ("workqueue: restore WQ_UNBOUND/max_active==1 to be
ordered") automatically enabled ordered attribute for unbound
workqueues w/ max_active == 1.  Because ordered workqueues reject
max_active and some attribute changes, this implicit ordered mode
broke cases where the user creates an unbound workqueue w/ max_active
== 1 and later explicitly changes the related attributes.

This patch distinguishes explicit and implicit ordered setting and
overrides from attribute changes if implict.

Signed-off-by: Tejun Heo <tj@kernel.org>
Fixes: 5c0338c687 ("workqueue: restore WQ_UNBOUND/max_active==1 to be ordered")

Tejun Heo   commited 2017-07-25 13:28:56 -04:00
0a94efb5ac
workqueue: restore WQ_UNBOUND/max_active==1 to be ordered 
The combination of WQ_UNBOUND and max_active == 1 used to imply
ordered execution.  After NUMA affinity 4c16bd327c ("workqueue:
implement NUMA affinity for unbound workqueues"), this is no longer
true due to per-node worker pools.

While the right way to create an ordered workqueue is
alloc_ordered_workqueue(), the documentation has been misleading for a
long time and people do use WQ_UNBOUND and max_active == 1 for ordered
workqueues which can lead to subtle bugs which are very difficult to
trigger.

It's unlikely that we'd see noticeable performance impact by enforcing
ordering on WQ_UNBOUND / max_active == 1 workqueues.  Let's
automatically set __WQ_ORDERED for those workqueues.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Christoph Hellwig <hch@infradead.org>
Reported-by: Alexei Potashnik <alexei@purestorage.com>
Fixes: 4c16bd327c ("workqueue: implement NUMA affinity for unbound workqueues")
Cc: stable@vger.kernel.org # v3.10+

Tejun Heo   commited 2017-07-19 11:24:19 -04:00
5c0338c687
sched/wait: Rename wait_queue_t => wait_queue_entry_t 
Rename:

	wait_queue_t		=>	wait_queue_entry_t

'wait_queue_t' was always a slight misnomer: its name implies that it's a "queue",
but in reality it's a queue *entry*. The 'real' queue is the wait queue head,
which had to carry the name.

Start sorting this out by renaming it to 'wait_queue_entry_t'.

This also allows the real structure name 'struct __wait_queue' to
lose its double underscore and become 'struct wait_queue_entry',
which is the more canonical nomenclature for such data types.

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Ingo Molnar   commited 2017-06-20 12:18:27 +02:00
ac6424b981
Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 
Pull scheduler updates from Ingo Molnar:
 "The main changes in this cycle were:

   - another round of rq-clock handling debugging, robustization and
     fixes

   - PELT accounting improvements

   - CPU hotplug related ->cpus_allowed affinity handling fixes all
     around the tree

   - ... plus misc fixes, cleanups and updates"

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (35 commits)
  sched/x86: Update reschedule warning text
  crypto: N2 - Replace racy task affinity logic
  cpufreq/sparc-us2e: Replace racy task affinity logic
  cpufreq/sparc-us3: Replace racy task affinity logic
  cpufreq/sh: Replace racy task affinity logic
  cpufreq/ia64: Replace racy task affinity logic
  ACPI/processor: Replace racy task affinity logic
  ACPI/processor: Fix error handling in __acpi_processor_start()
  sparc/sysfs: Replace racy task affinity logic
  powerpc/smp: Replace open coded task affinity logic
  ia64/sn/hwperf: Replace racy task affinity logic
  ia64/salinfo: Replace racy task affinity logic
  workqueue: Provide work_on_cpu_safe()
  ia64/topology: Remove cpus_allowed manipulation
  sched/fair: Move the PELT constants into a generated header
  sched/fair: Increase PELT accuracy for small tasks
  sched/fair: Fix comments
  sched/Documentation: Add 'sched-pelt' tool
  sched/fair: Fix corner case in __accumulate_sum()
  sched/core: Remove 'task' parameter and rename tsk_restore_flags() to current_restore_flags()
  ...

Linus Torvalds   commited 2017-05-01 19:12:53 -07:00
3527d3e951
Merge branch 'for-4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 
Pull workqueue update from Tejun Heo:
 "One trivial patch to use setup_deferrable_timer() instead of
  open-coding the initialization"

* 'for-4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
  workqueue: use setup_deferrable_timer

Linus Torvalds   commited 2017-05-01 13:49:27 -07:00
ad1490bcd2
workqueue: Provide work_on_cpu_safe() 
work_on_cpu() is not protected against CPU hotplug. For code which requires
to be either executed on an online CPU or to fail if the CPU is not
available the callsite would have to protect against CPU hotplug.

Provide a function which does get/put_online_cpus() around the call to
work_on_cpu() and fails the call with -ENODEV if the target CPU is not
online.

Preparatory patch to convert several racy task affinity manipulations.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Len Brown <lenb@kernel.org>
Link: http://lkml.kernel.org/r/20170412201042.262610721@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Thomas Gleixner   commited 2017-04-15 12:20:53 +02:00
0e8d6a9336
workqueue: use setup_deferrable_timer 
Use setup_deferrable_timer() instead of init_timer_deferrable() to
simplify the code.

Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

Geliang Tang   authored and   Tejun Heo   commited 2017-03-06 15:42:20 -05:00
c30fb26b11
workqueue: trigger WARN if queue_delayed_work() is called with NULL @wq 
If queue_delayed_work() gets called with NULL @wq, the kernel will
oops asynchronuosly on timer expiration which isn't too helpful in
tracking down the offender.  This actually happened with smc.

__queue_delayed_work() already does several input sanity checks
synchronously.  Add NULL @wq check.

Reported-by: Dave Jones <davej@codemonkey.org.uk>
Link: http://lkml.kernel.org/r/20170227171439.jshx3qplflyrgcv7@codemonkey.org.uk
Signed-off-by: Tejun Heo <tj@kernel.org>

Tejun Heo   commited 2017-03-06 15:33:42 -05:00
637fdbae60
time: Remove CONFIG_TIMER_STATS 
Currently CONFIG_TIMER_STATS exposes process information across namespaces:

kernel/time/timer_list.c print_timer():

        SEQ_printf(m, ", %s/%d", tmp, timer->start_pid);

/proc/timer_list:

 #11: <0000000000000000>, hrtimer_wakeup, S:01, do_nanosleep, cron/2570

Given that the tracer can give the same information, this patch entirely
removes CONFIG_TIMER_STATS.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: John Stultz <john.stultz@linaro.org>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: linux-doc@vger.kernel.org
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Xing Gao <xgao01@email.wm.edu>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Jessica Frazelle <me@jessfraz.com>
Cc: kernel-hardening@lists.openwall.com
Cc: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Michal Marek <mmarek@suse.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Olof Johansson <olof@lixom.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-api@vger.kernel.org
Cc: Arjan van de Ven <arjan@linux.intel.com>
Link: http://lkml.kernel.org/r/20170208192659.GA32582@beast
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Kees Cook   authored and   Thomas Gleixner   commited 2017-02-10 11:15:08 +01:00
dfb4357da6
Merge branch 'for-4.9' into for-4.10
Tejun Heo   commited 2016-10-19 12:12:40 -04:00
8bc4a04455
workqueue: move wq_numa_init() to workqueue_init() 
While splitting up workqueue initialization into two parts,
ac8f73400782 ("workqueue: make workqueue available early during boot")
put wq_numa_init() into workqueue_init_early().  Unfortunately, on
some archs including power and arm64, cpu to node mapping isn't yet
established by the time the early init is called leading to incorrect
NUMA initialization and subsequently the following oops due to zero
cpumask on node-specific unbound pools.

  Unable to handle kernel paging request for data at address 0x00000038
  Faulting instruction address: 0xc0000000000fc0cc
  Oops: Kernel access of bad area, sig: 11 [#1]
  SMP NR_CPUS=2048 NUMA PowerNV
  Modules linked in:
  CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.8.0-compiler_gcc-6.2.0-next-20161005 #94
  task: c0000007f5400000 task.stack: c000001ffc084000
  NIP: c0000000000fc0cc LR: c0000000000ed928 CTR: c0000000000fbfd0
  REGS: c000001ffc087780 TRAP: 0300   Not tainted  (4.8.0-compiler_gcc-6.2.0-next-20161005)
  MSR: 9000000002009033 <SF,HV,VEC,EE,ME,IR,DR,RI,LE>  CR: 48000424  XER: 00000000
  CFAR: c0000000000089dc DAR: 0000000000000038 DSISR: 40000000 SOFTE: 0
  GPR00: c0000000000ed928 c000001ffc087a00 c000000000e63200 c000000010d6d600
  GPR04: c0000007f5409200 0000000000000021 000000000748e08c 000000000000001f
  GPR08: 0000000000000000 0000000000000021 000000000748f1f8 0000000000000000
  GPR12: 0000000028000422 c00000000fb80000 c00000000000e0c8 0000000000000000
  GPR16: 0000000000000000 0000000000000000 0000000000000021 0000000000000001
  GPR20: ffffffffafb50401 0000000000000000 c000000010d6d600 000000000000ba7e
  GPR24: 000000000000ba7e c000000000d8bc58 afb504000afb5041 0000000000000001
  GPR28: 0000000000000000 0000000000000004 c0000007f5409280 0000000000000000
  NIP [c0000000000fc0cc] enqueue_task_fair+0xfc/0x18b0
  LR [c0000000000ed928] activate_task+0x78/0xe0
  Call Trace:
  [c000001ffc087a00] [c0000007f5409200] 0xc0000007f5409200 (unreliable)
  [c000001ffc087b10] [c0000000000ed928] activate_task+0x78/0xe0
  [c000001ffc087b50] [c0000000000ede58] ttwu_do_activate+0x68/0xc0
  [c000001ffc087b90] [c0000000000ef1b8] try_to_wake_up+0x208/0x4f0
  [c000001ffc087c10] [c0000000000d3484] create_worker+0x144/0x250
  [c000001ffc087cb0] [c000000000cd72d0] workqueue_init+0x124/0x150
  [c000001ffc087d00] [c000000000cc0e74] kernel_init_freeable+0x158/0x360
  [c000001ffc087dc0] [c00000000000e0e4] kernel_init+0x24/0x160
  [c000001ffc087e30] [c00000000000bfa0] ret_from_kernel_thread+0x5c/0xbc
  Instruction dump:
  62940401 3b800000 3aa00000 7f17c378 3a600001 3b600001 60000000 60000000
  60420000 72490021 ebfe0150 2f890001 <ebbf0038> 419e0de0 7fbee840 419e0e58
  ---[ end trace 0000000000000000 ]---

Fix it by moving wq_numa_init() to workqueue_init().  As this means
that the early intialization may not have full NUMA info for per-cpu
pools and ignores NUMA affinity for unbound pools, fix them up from
workqueue_init() after wq_numa_init().

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Michael Ellerman <mpe@ellerman.id.au>
Link: http://lkml.kernel.org/r/87twck5wqo.fsf@concordia.ellerman.id.au
Fixes: ac8f73400782 ("workqueue: make workqueue available early during boot")
Signed-off-by: Tejun Heo <tj@kernel.org>

Tejun Heo   commited 2016-10-19 12:12:26 -04:00
2186d9f940
kthread: rename probe_kthread_data() to kthread_probe_data() 
Patch series "kthread: Kthread worker API improvements"

The intention of this patchset is to make it easier to manipulate and
maintain kthreads.  Especially, I want to replace all the custom main
cycles with a generic one.  Also I want to make the kthreads sleep in a
consistent state in a common place when there is no work.

This patch (of 11):

A good practice is to prefix the names of functions by the name of the
subsystem.

This patch fixes the name of probe_kthread_data().  The other wrong
functions names are part of the kthread worker API and will be fixed
separately.

Link: http://lkml.kernel.org/r/1470754545-17632-2-git-send-email-pmladek@suse.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Borislav Petkov <bp@suse.de>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Petr Mladek   authored and   Linus Torvalds   commited 2016-10-11 15:06:33 -07:00
e700591ae0
workqueue: remove keventd_up() 
keventd_up() no longer has in-kernel users.  Remove it and make
wq_online static.

Signed-off-by: Tejun Heo <tj@kernel.org>

Tejun Heo   commited 2016-09-17 13:18:21 -04:00
863b710b66
workqueue: make workqueue available early during boot 
Workqueue is currently initialized in an early init call; however,
there are cases where early boot code has to be split and reordered to
come after workqueue initialization or the same code path which makes
use of workqueues is used both before workqueue initailization and
after.  The latter cases have to gate workqueue usages with
keventd_up() tests, which is nasty and easy to get wrong.

Workqueue usages have become widespread and it'd be a lot more
convenient if it can be used very early from boot.  This patch splits
workqueue initialization into two steps.  workqueue_init_early() which
sets up the basic data structures so that workqueues can be created
and work items queued, and workqueue_init() which actually brings up
workqueues online and starts executing queued work items.  The former
step can be done very early during boot once memory allocation,
cpumasks and idr are initialized.  The latter right after kthreads
become available.

This allows work item queueing and canceling from very early boot
which is what most of these use cases want.

* As systemd_wq being initialized doesn't indicate that workqueue is
  fully online anymore, update keventd_up() to test wq_online instead.
  The follow-up patches will get rid of all its usages and the
  function itself.

* Flushing doesn't make sense before workqueue is fully initialized.
  The flush functions trigger WARN and return immediately before fully
  online.

* Work items are never in-flight before fully online.  Canceling can
  always succeed by skipping the flush step.

* Some code paths can no longer assume to be called with irq enabled
  as irq is disabled during early boot.  Use irqsave/restore
  operations instead.

v2: Watchdog init, which requires timer to be running, moved from
    workqueue_init_early() to workqueue_init().

Signed-off-by: Tejun Heo <tj@kernel.org>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/CA+55aFx0vPuMuxn00rBSM192n-Du5uxy+4AvKa0SBSOVJeuCGg@mail.gmail.com

Tejun Heo   commited 2016-09-17 13:18:21 -04:00
3347fa0928
workqueue: dump workqueue state on sanity check failures in destroy_workqueue() 
destroy_workqueue() performs a number of sanity checks to ensure that
the workqueue is empty before proceeding with destruction.  However,
it's not always easy to tell what's going on just from the warning
message.  Let's dump workqueue state after sanity check failures to
help debugging.

Signed-off-by: Tejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/r/CACT4Y+Zs6vkjHo9qHb4TrEiz3S4+quvvVQ9VWvj2Mx6pETGb9Q@mail.gmail.com
Cc: Dmitry Vyukov <dvyukov@google.com>

Tejun Heo   commited 2016-09-16 11:08:39 -04:00
fa07fb6a4e
workqueue: add cancel_work() 
Like cancel_delayed_work(), but for regular work.

Signed-off-by: Jens Axboe <axboe@fb.com>
Mehed-by: Tejun Heo <tj@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>

Jens Axboe   commited 2016-08-29 08:13:21 -06:00
f72b8792d1
Merge branch 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 
Pull smp hotplug updates from Thomas Gleixner:
 "This is the next part of the hotplug rework.

   - Convert all notifiers with a priority assigned

   - Convert all CPU_STARTING/DYING notifiers

     The final removal of the STARTING/DYING infrastructure will happen
     when the merge window closes.

  Another 700 hundred line of unpenetrable maze gone :)"

* 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (70 commits)
  timers/core: Correct callback order during CPU hot plug
  leds/trigger/cpu: Move from CPU_STARTING to ONLINE level
  powerpc/numa: Convert to hotplug state machine
  arm/perf: Fix hotplug state machine conversion
  irqchip/armada: Avoid unused function warnings
  ARC/time: Convert to hotplug state machine
  clocksource/atlas7: Convert to hotplug state machine
  clocksource/armada-370-xp: Convert to hotplug state machine
  clocksource/exynos_mct: Convert to hotplug state machine
  clocksource/arm_global_timer: Convert to hotplug state machine
  rcu: Convert rcutree to hotplug state machine
  KVM/arm/arm64/vgic-new: Convert to hotplug state machine
  smp/cfd: Convert core to hotplug state machine
  x86/x2apic: Convert to CPU hotplug state machine
  profile: Convert to hotplug state machine
  timers/core: Convert to hotplug state machine
  hrtimer: Convert to hotplug state machine
  x86/tboot: Convert to hotplug state machine
  arm64/armv8 deprecated: Convert to hotplug state machine
  hwtracing/coresight-etm4x: Convert to hotplug state machine
  ...

Linus Torvalds   commited 2016-07-29 13:55:30 -07:00
a6408f6cb6
Merge branches 'pm-sleep' and 'pm-tools' 
* pm-sleep:
  PM / hibernate: Introduce test_resume mode for hibernation
  x86 / hibernate: Use hlt_play_dead() when resuming from hibernation
  PM / hibernate: Image data protection during restoration
  PM / hibernate: Add missing braces in __register_nosave_region()
  PM / hibernate: Clean up comments in snapshot.c
  PM / hibernate: Clean up function headers in snapshot.c
  PM / hibernate: Add missing braces in hibernate_setup()
  PM / hibernate: Recycle safe pages after image restoration
  PM / hibernate: Simplify mark_unsafe_pages()
  PM / hibernate: Do not free preallocated safe pages during image restore
  PM / suspend: show workqueue state in suspend flow
  PM / sleep: make PM notifiers called symmetrically
  PM / sleep: Make pm_prepare_console() return void
  PM / Hibernate: Don't let kasan instrument snapshot.c

* pm-tools:
  PM / tools: scripts: AnalyzeSuspend v4.2
  tools/turbostat: allow user to alter DESTDIR and PREFIX

Rafael J. Wysocki   commited 2016-07-25 13:44:32 +02:00
7f234a4d8a
workqueue: Convert to state machine callbacks 
Get rid of the prio ordering of the separate notifiers and use a proper state
callback pair.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160713153335.197083890@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Thomas Gleixner   authored and   Ingo Molnar   commited 2016-07-14 09:34:43 +02:00
7ee681b252
PM / suspend: show workqueue state in suspend flow 
If freezable workqueue aborts suspend flow, show
workqueue state for debug purpose.

Signed-off-by: Roger Lu <roger.lu@mediatek.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Roger Lu   authored and   Rafael J. Wysocki   commited 2016-07-02 01:42:48 +02:00
7b776af66d
workqueue: Fix setting affinity of unbound worker threads 
With commit e9d867a67f ("sched: Allow per-cpu kernel threads to
run on online && !active"), __set_cpus_allowed_ptr() expects that only
strict per-cpu kernel threads can have affinity to an online CPU which
is not yet active.

This assumption is currently broken in the CPU_ONLINE notification
handler for the workqueues where restore_unbound_workers_cpumask()
calls set_cpus_allowed_ptr() when the first cpu in the unbound
worker's pool->attr->cpumask comes online. Since
set_cpus_allowed_ptr() is called with pool->attr->cpumask in which
only one CPU is online which is not yet active, we get the following
WARN_ON during an CPU online operation.

------------[ cut here ]------------
WARNING: CPU: 40 PID: 248 at kernel/sched/core.c:1166
__set_cpus_allowed_ptr+0x228/0x2e0
Modules linked in:
CPU: 40 PID: 248 Comm: cpuhp/40 Not tainted 4.6.0-autotest+ #4
<..snip..>
Call Trace:
[c000000f273ff920] [c00000000010493c] __set_cpus_allowed_ptr+0x2cc/0x2e0 (unreliable)
[c000000f273ffac0] [c0000000000ed4b0] workqueue_cpu_up_callback+0x2c0/0x470
[c000000f273ffb70] [c0000000000f5c58] notifier_call_chain+0x98/0x100
[c000000f273ffbc0] [c0000000000c5ed0] __cpu_notify+0x70/0xe0
[c000000f273ffc00] [c0000000000c6028] notify_online+0x38/0x50
[c000000f273ffc30] [c0000000000c5214] cpuhp_invoke_callback+0x84/0x250
[c000000f273ffc90] [c0000000000c562c] cpuhp_up_callbacks+0x5c/0x120
[c000000f273ffce0] [c0000000000c64d4] cpuhp_thread_fun+0x184/0x1c0
[c000000f273ffd20] [c0000000000fa050] smpboot_thread_fn+0x290/0x2a0
[c000000f273ffd80] [c0000000000f45b0] kthread+0x110/0x130
[c000000f273ffe30] [c000000000009570] ret_from_kernel_thread+0x5c/0x6c
---[ end trace 00f1456578b2a3b2 ]---

This patch fixes this by limiting the mask to the intersection of
the pool affinity and online CPUs.

Changelog-cribbed-from: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Reported-by: Abdul Haleem <abdhalee@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Tejun Heo <tj@kernel.org>

Peter Zijlstra   authored and   Tejun Heo   commited 2016-06-16 15:37:05 -04:00
d945b5e9f0
debugobjects: insulate non-fixup logic related to static obj from fixup callbacks 
When activating a static object we need make sure that the object is
tracked in the object tracker.  If it is a non-static object then the
activation is illegal.

In previous implementation, each subsystem need take care of this in
their fixup callbacks.  Actually we can put it into debugobjects core.
Thus we can save duplicated code, and have *pure* fixup callbacks.

To achieve this, a new callback "is_static_object" is introduced to let
the type specific code decide whether a object is static or not.  If
yes, we take it into object tracker, otherwise give warning and invoke
fixup callback.

This change has paassed debugobjects selftest, and I also do some test
with all debugobjects supports enabled.

At last, I have a concern about the fixups that can it change the object
which is in incorrect state on fixup? Because the 'addr' may not point
to any valid object if a non-static object is not tracked.  Then Change
such object can overwrite someone's memory and cause unexpected
behaviour.  For example, the timer_fixup_activate bind timer to function
stub_timer.

Link: http://lkml.kernel.org/r/1462576157-14539-1-git-send-email-changbin.du@intel.com
[changbin.du@intel.com: improve code comments where invoke the new is_static_object callback]
  Link: http://lkml.kernel.org/r/1462777431-8171-1-git-send-email-changbin.du@intel.com
Signed-off-by: Du, Changbin <changbin.du@intel.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Josh Triplett <josh@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Du, Changbin   authored and   Linus Torvalds   commited 2016-05-19 19:12:14 -07:00
b9fdac7f66
workqueue: update debugobjects fixup callbacks return type 
Update the return type to use bool instead of int, corresponding to
change (debugobjects: make fixup functions return bool instead of int)

Signed-off-by: Du, Changbin <changbin.du@intel.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Josh Triplett <josh@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Du, Changbin   authored and   Linus Torvalds   commited 2016-05-19 19:12:14 -07:00
02a982a6ec
Merge branch 'for-4.6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 
Pull workqueue fix from Tejun Heo:
 "CPU hotplug callbacks can invoke DOWN_FAILED w/o preceding
  DOWN_PREPARE which can trigger a WARN_ON() in workqueue.

  The bug has been there for a very long time.  It only triggers if CPU
  down fails at a specific point and I don't think it has adverse
  effects other than the warning messages.  The fix is very low impact"

* 'for-4.6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
  workqueue: fix rebind bound workers warning

Linus Torvalds   commited 2016-05-13 16:16:51 -07:00
da92223908
workqueue: fix rebind bound workers warning 
------------[ cut here ]------------
WARNING: CPU: 0 PID: 16 at kernel/workqueue.c:4559 rebind_workers+0x1c0/0x1d0
Modules linked in:
CPU: 0 PID: 16 Comm: cpuhp/0 Not tainted 4.6.0-rc4+ #31
Hardware name: IBM IBM System x3550 M4 Server -[7914IUW]-/00Y8603, BIOS -[D7E128FUS-1.40]- 07/23/2013
 0000000000000000 ffff881037babb58 ffffffff8139d885 0000000000000010
 0000000000000000 0000000000000000 0000000000000000 ffff881037babba8
 ffffffff8108505d ffff881037ba0000 000011cf3e7d6e60 0000000000000046
Call Trace:
 dump_stack+0x89/0xd4
 __warn+0xfd/0x120
 warn_slowpath_null+0x1d/0x20
 rebind_workers+0x1c0/0x1d0
 workqueue_cpu_up_callback+0xf5/0x1d0
 notifier_call_chain+0x64/0x90
 ? trace_hardirqs_on_caller+0xf2/0x220
 ? notify_prepare+0x80/0x80
 __raw_notifier_call_chain+0xe/0x10
 __cpu_notify+0x35/0x50
 notify_down_prepare+0x5e/0x80
 ? notify_prepare+0x80/0x80
 cpuhp_invoke_callback+0x73/0x330
 ? __schedule+0x33e/0x8a0
 cpuhp_down_callbacks+0x51/0xc0
 cpuhp_thread_fun+0xc1/0xf0
 smpboot_thread_fn+0x159/0x2a0
 ? smpboot_create_threads+0x80/0x80
 kthread+0xef/0x110
 ? wait_for_completion+0xf0/0x120
 ? schedule_tail+0x35/0xf0
 ret_from_fork+0x22/0x50
 ? __init_kthread_worker+0x70/0x70
---[ end trace eb12ae47d2382d8f ]---
notify_down_prepare: attempt to take down CPU 0 failed

This bug can be reproduced by below config w/ nohz_full= all cpus:

CONFIG_BOOTPARAM_HOTPLUG_CPU0=y
CONFIG_DEBUG_HOTPLUG_CPU0=y
CONFIG_NO_HZ_FULL=y

As Thomas pointed out:

| If a down prepare callback fails, then DOWN_FAILED is invoked for all
| callbacks which have successfully executed DOWN_PREPARE.
|
| But, workqueue has actually two notifiers. One which handles
| UP/DOWN_FAILED/ONLINE and one which handles DOWN_PREPARE.
|
| Now look at the priorities of those callbacks:
|
| CPU_PRI_WORKQUEUE_UP        = 5
| CPU_PRI_WORKQUEUE_DOWN      = -5
|
| So the call order on DOWN_PREPARE is:
|
| CB 1
| CB ...
| CB workqueue_up() -> Ignores DOWN_PREPARE
| CB ...
| CB X ---> Fails
|
| So we call up to CB X with DOWN_FAILED
|
| CB 1
| CB ...
| CB workqueue_up() -> Handles DOWN_FAILED
| CB ...
| CB X-1
|
| So the problem is that the workqueue stuff handles DOWN_FAILED in the up
| callback, while it should do it in the down callback. Which is not a good idea
| either because it wants to be called early on rollback...
|
| Brilliant stuff, isn't it? The hotplug rework will solve this problem because
| the callbacks become symetric, but for the existing mess, we need some
| workaround in the workqueue code.

The boot CPU handles housekeeping duty(unbound timers, workqueues,
timekeeping, ...) on behalf of full dynticks CPUs. It must remain
online when nohz full is enabled. There is a priority set to every
notifier_blocks:

workqueue_cpu_up > tick_nohz_cpu_down > workqueue_cpu_down

So tick_nohz_cpu_down callback failed when down prepare cpu 0, and
notifier_blocks behind tick_nohz_cpu_down will not be called any
more, which leads to workers are actually not unbound. Then hotplug
state machine will fallback to undo and online cpu 0 again. Workers
will be rebound unconditionally even if they are not unbound and
trigger the warning in this progress.

This patch fix it by catching !DISASSOCIATED to avoid rebind bound
workers.

Cc: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: stable@vger.kernel.org
Suggested-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>

Wanpeng Li   authored and   Tejun Heo   commited 2016-05-12 12:00:23 -04:00
f7c17d26f4
Merge branch 'for-4.6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 
Pull workqueue fix from Tejun Heo:
 "So, it turns out we had a silly bug in the most fundamental part of
  workqueue for a very long time.  AFAICS, this dates back to pre-git
  era and has quite likely been there from the time workqueue was first
  introduced.

  A work item uses its PENDING bit to synchronize multiple queuers.
  Anyone who wins the PENDING bit owns the pending state of the work
  item.  Whether a queuer wins or loses the race, one thing should be
  guaranteed - there will soon be at least one execution of the work
  item - where "after" means that the execution instance would be able
  to see all the changes that the queuer has made prior to the queueing
  attempt.

  Unfortunately, we were missing a smp_mb() after clearing PENDING for
  execution, so nothing guaranteed visibility of the changes that a
  queueing loser has made, which manifested as a reproducible blk-mq
  stall.

  Lots of kudos to Roman for debugging the problem.  The patch for
  -stable is the minimal one.  For v3.7, Peter is working on a patch to
  make the code path slightly more efficient and less fragile"

* 'for-4.6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
  workqueue: fix ghost PENDING flag while doing MQ IO

Linus Torvalds   commited 2016-04-27 12:03:59 -07:00
b75a2bf899
workqueue: fix ghost PENDING flag while doing MQ IO 
The bug in a workqueue leads to a stalled IO request in MQ ctx->rq_list
with the following backtrace:

[  601.347452] INFO: task kworker/u129:5:1636 blocked for more than 120 seconds.
[  601.347574]       Tainted: G           O    4.4.5-1-storage+ #6
[  601.347651] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  601.348142] kworker/u129:5  D ffff880803077988     0  1636      2 0x00000000
[  601.348519] Workqueue: ibnbd_server_fileio_wq ibnbd_dev_file_submit_io_worker [ibnbd_server]
[  601.348999]  ffff880803077988 ffff88080466b900 ffff8808033f9c80 ffff880803078000
[  601.349662]  ffff880807c95000 7fffffffffffffff ffffffff815b0920 ffff880803077ad0
[  601.350333]  ffff8808030779a0 ffffffff815b01d5 0000000000000000 ffff880803077a38
[  601.350965] Call Trace:
[  601.351203]  [<ffffffff815b0920>] ? bit_wait+0x60/0x60
[  601.351444]  [<ffffffff815b01d5>] schedule+0x35/0x80
[  601.351709]  [<ffffffff815b2dd2>] schedule_timeout+0x192/0x230
[  601.351958]  [<ffffffff812d43f7>] ? blk_flush_plug_list+0xc7/0x220
[  601.352208]  [<ffffffff810bd737>] ? ktime_get+0x37/0xa0
[  601.352446]  [<ffffffff815b0920>] ? bit_wait+0x60/0x60
[  601.352688]  [<ffffffff815af784>] io_schedule_timeout+0xa4/0x110
[  601.352951]  [<ffffffff815b3a4e>] ? _raw_spin_unlock_irqrestore+0xe/0x10
[  601.353196]  [<ffffffff815b093b>] bit_wait_io+0x1b/0x70
[  601.353440]  [<ffffffff815b056d>] __wait_on_bit+0x5d/0x90
[  601.353689]  [<ffffffff81127bd0>] wait_on_page_bit+0xc0/0xd0
[  601.353958]  [<ffffffff81096db0>] ? autoremove_wake_function+0x40/0x40
[  601.354200]  [<ffffffff81127cc4>] __filemap_fdatawait_range+0xe4/0x140
[  601.354441]  [<ffffffff81127d34>] filemap_fdatawait_range+0x14/0x30
[  601.354688]  [<ffffffff81129a9f>] filemap_write_and_wait_range+0x3f/0x70
[  601.354932]  [<ffffffff811ced3b>] blkdev_fsync+0x1b/0x50
[  601.355193]  [<ffffffff811c82d9>] vfs_fsync_range+0x49/0xa0
[  601.355432]  [<ffffffff811cf45a>] blkdev_write_iter+0xca/0x100
[  601.355679]  [<ffffffff81197b1a>] __vfs_write+0xaa/0xe0
[  601.355925]  [<ffffffff81198379>] vfs_write+0xa9/0x1a0
[  601.356164]  [<ffffffff811c59d8>] kernel_write+0x38/0x50

The underlying device is a null_blk, with default parameters:

  queue_mode    = MQ
  submit_queues = 1

Verification that nullb0 has something inflight:

root@pserver8:~# cat /sys/block/nullb0/inflight
       0        1
root@pserver8:~# find /sys/block/nullb0/mq/0/cpu* -name rq_list -print -exec cat {} \;
...
/sys/block/nullb0/mq/0/cpu2/rq_list
CTX pending:
        ffff8838038e2400
...

During debug it became clear that stalled request is always inserted in
the rq_list from the following path:

   save_stack_trace_tsk + 34
   blk_mq_insert_requests + 231
   blk_mq_flush_plug_list + 281
   blk_flush_plug_list + 199
   wait_on_page_bit + 192
   __filemap_fdatawait_range + 228
   filemap_fdatawait_range + 20
   filemap_write_and_wait_range + 63
   blkdev_fsync + 27
   vfs_fsync_range + 73
   blkdev_write_iter + 202
   __vfs_write + 170
   vfs_write + 169
   kernel_write + 56

So blk_flush_plug_list() was called with from_schedule == true.

If from_schedule is true, that means that finally blk_mq_insert_requests()
offloads execution of __blk_mq_run_hw_queue() and uses kblockd workqueue,
i.e. it calls kblockd_schedule_delayed_work_on().

That means, that we race with another CPU, which is about to execute
__blk_mq_run_hw_queue() work.

Further debugging shows the following traces from different CPUs:

  CPU#0                                  CPU#1
  ----------------------------------     -------------------------------
  reqeust A inserted
  STORE hctx->ctx_map[0] bit marked
  kblockd_schedule...() returns 1
  <schedule to kblockd workqueue>
                                         request B inserted
                                         STORE hctx->ctx_map[1] bit marked
                                         kblockd_schedule...() returns 0
  *** WORK PENDING bit is cleared ***
  flush_busy_ctxs() is executed, but
  bit 1, set by CPU#1, is not observed

As a result request B pended forever.

This behaviour can be explained by speculative LOAD of hctx->ctx_map on
CPU#0, which is reordered with clear of PENDING bit and executed _before_
actual STORE of bit 1 on CPU#1.

The proper fix is an explicit full barrier <mfence>, which guarantees
that clear of PENDING bit is to be executed before all possible
speculative LOADS or STORES inside actual work function.

Signed-off-by: Roman Pen <roman.penyaev@profitbricks.com>
Cc: Gioh Kim <gi-oh.kim@profitbricks.com>
Cc: Michael Wang <yun.wang@profitbricks.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org
Signed-off-by: Tejun Heo <tj@kernel.org>

Roman Pen   authored and   Tejun Heo   commited 2016-04-26 11:23:22 -04:00
346c09f804