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  1. 02 12月, 2012 6 次提交
    • L
      Merge branch 'for-3.7-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq · 3c46f3d6
      由 Linus Torvalds 提交于 
      Pull  late workqueue fixes from Tejun Heo:
 "Unfortunately, I have two really late fixes.  One was for a
  long-standing bug and queued for 3.8 but I found out about a
  regression introduced during 3.7-rc1 two days ago, so I'm sending out
  the two fixes together.

  The first (long-standing) one is rescuer_thread() entering exit path
  w/ TASK_INTERRUPTIBLE.  It only triggers on workqueue destructions
  which isn't very frequent and the exit path can usually survive being
  called with TASK_INTERRUPT, so it was hidden pretty well.  Apparently,
  if you're reiserfs, this could lead to the exiting kthread sleeping
  indefinitely holding a mutex, which is never good.

  The fix is simple - restoring TASK_RUNNING before returning from the
  kthread function.

  The second one is introduced by the new mod_delayed_work().
  mod_delayed_work() was missing special case handling for 0 delay.
  Instead of queueing the work item immediately, it queued the timer
  which expires on the closest next tick.  Some users of the new
  function converted from "[__]cancel_delayed_work() +
  queue_delayed_work()" combination became unhappy with the extra delay.

  Block unplugging led to noticeably higher number of context switches
  and intel 6250 wireless failed to associate with WPA-Enterprise
  network.  The fix, again, is fairly simple.  The 0 delay special case
  logic from queue_delayed_work_on() should be moved to
  __queue_delayed_work() which is shared by both queue_delayed_work_on()
  and mod_delayed_work_on().

  The first one is difficult to trigger and the failure mode for the
  latter isn't completely catastrophic, so missing these two for 3.7
  wouldn't make it a disastrous release, but both bugs are nasty and the
  fixes are fairly safe"

* 'for-3.7-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
  workqueue: mod_delayed_work_on() shouldn't queue timer on 0 delay
  workqueue: exit rescuer_thread() as TASK_RUNNING
      3c46f3d6
    • T
      workqueue: mod_delayed_work_on() shouldn't queue timer on 0 delay · 8852aac2
      由 Tejun Heo 提交于 
      8376fe22 ("workqueue: implement mod_delayed_work[_on]()")
implemented mod_delayed_work[_on]() using the improved
try_to_grab_pending().  The function is later used, among others, to
replace [__]candel_delayed_work() + queue_delayed_work() combinations.

Unfortunately, a delayed_work item w/ zero @delay is handled slightly
differently by mod_delayed_work_on() compared to
queue_delayed_work_on().  The latter skips timer altogether and
directly queues it using queue_work_on() while the former schedules
timer which will expire on the closest tick.  This means, when @delay
is zero, that [__]cancel_delayed_work() + queue_delayed_work_on()
makes the target item immediately executable while
mod_delayed_work_on() may induce delay of upto a full tick.

This somewhat subtle difference breaks some of the converted users.
e.g. block queue plugging uses delayed_work for deferred processing
and uses mod_delayed_work_on() when the queue needs to be immediately
unplugged.  The above problem manifested as noticeably higher number
of context switches under certain circumstances.

The difference in behavior was caused by missing special case handling
for 0 delay in mod_delayed_work_on() compared to
queue_delayed_work_on().  Joonsoo Kim posted a patch to add it -
("workqueue: optimize mod_delayed_work_on() when @delay == 0")[1].
The patch was queued for 3.8 but it was described as optimization and
I missed that it was a correctness issue.

As both queue_delayed_work_on() and mod_delayed_work_on() use
__queue_delayed_work() for queueing, it seems that the better approach
is to move the 0 delay special handling to the function instead of
duplicating it in mod_delayed_work_on().

Fix the problem by moving 0 delay special case handling from
queue_delayed_work_on() to __queue_delayed_work().  This replaces
Joonsoo's patch.

[1] http://thread.gmane.org/gmane.linux.kernel/1379011/focus=1379012Signed-off-by: NTejun Heo <tj@kernel.org>
Reported-and-tested-by: NAnders Kaseorg <andersk@MIT.EDU>
Reported-and-tested-by: NZlatko Calusic <zlatko.calusic@iskon.hr>
LKML-Reference: <alpine.DEB.2.00.1211280953350.26602@dr-wily.mit.edu>
LKML-Reference: <50A78AA9.5040904@iskon.hr>
Cc: Joonsoo Kim <js1304@gmail.com>
      8852aac2
    • M
      workqueue: exit rescuer_thread() as TASK_RUNNING · 412d32e6
      由 Mike Galbraith 提交于 
      A rescue thread exiting TASK_INTERRUPTIBLE can lead to a task scheduling
off, never to be seen again.  In the case where this occurred, an exiting
thread hit reiserfs homebrew conditional resched while holding a mutex,
bringing the box to its knees.

PID: 18105  TASK: ffff8807fd412180  CPU: 5   COMMAND: "kdmflush"
 #0 [ffff8808157e7670] schedule at ffffffff8143f489
 #1 [ffff8808157e77b8] reiserfs_get_block at ffffffffa038ab2d [reiserfs]
 #2 [ffff8808157e79a8] __block_write_begin at ffffffff8117fb14
 #3 [ffff8808157e7a98] reiserfs_write_begin at ffffffffa0388695 [reiserfs]
 #4 [ffff8808157e7ad8] generic_perform_write at ffffffff810ee9e2
 #5 [ffff8808157e7b58] generic_file_buffered_write at ffffffff810eeb41
 #6 [ffff8808157e7ba8] __generic_file_aio_write at ffffffff810f1a3a
 #7 [ffff8808157e7c58] generic_file_aio_write at ffffffff810f1c88
 #8 [ffff8808157e7cc8] do_sync_write at ffffffff8114f850
 #9 [ffff8808157e7dd8] do_acct_process at ffffffff810a268f
    [exception RIP: kernel_thread_helper]
    RIP: ffffffff8144a5c0  RSP: ffff8808157e7f58  RFLAGS: 00000202
    RAX: 0000000000000000  RBX: 0000000000000000  RCX: 0000000000000000
    RDX: 0000000000000000  RSI: ffffffff8107af60  RDI: ffff8803ee491d18
    RBP: 0000000000000000   R8: 0000000000000000   R9: 0000000000000000
    R10: 0000000000000000  R11: 0000000000000000  R12: 0000000000000000
    R13: 0000000000000000  R14: 0000000000000000  R15: 0000000000000000
    ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
Signed-off-by: NMike Galbraith <mgalbraith@suse.de>
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: stable@vger.kernel.org
      412d32e6
    • L
      Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs · 331fee3c
      由 Linus Torvalds 提交于 
      Pull vfs fixes from Al Viro:
 "A bunch of fixes; the last one is this cycle regression, the rest are
  -stable fodder."

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  fix off-by-one in argument passed by iterate_fd() to callbacks
  lookup_one_len: don't accept . and ..
  cifs: get rid of blind d_drop() in readdir
  nfs_lookup_revalidate(): fix a leak
  don't do blind d_drop() in nfs_prime_dcache()
      331fee3c
    • L
      Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip · b3c3a9cf
      由 Linus Torvalds 提交于 
      Pull RCU fix from Ingo Molnar:
 "Fix leaking RCU extended quiescent state, which might trigger warnings
  and mess up the extended quiescent state tracking logic into thinking
  that we are in "RCU user mode" while we aren't."

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  rcu: Fix unrecovered RCU user mode in syscall_trace_leave()
      b3c3a9cf
    • L
      Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip · 455e987c
      由 Linus Torvalds 提交于 
      Pull perf fixes from Ingo Molnar:
 "This is mostly about unbreaking architectures that took the UAPI
  changes in the v3.7 cycle, plus misc fixes."

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf kvm: Fix building perf kvm on non x86 arches
  perf kvm: Rename perf_kvm to perf_kvm_stat
  perf: Make perf build for x86 with UAPI disintegration applied
  perf powerpc: Use uapi/unistd.h to fix build error
  tools: Pass the target in descend
  tools: Honour the O= flag when tool build called from a higher Makefile
  tools: Define a Makefile function to do subdir processing
  x86: Export asm/{svm.h,vmx.h,perf_regs.h}
  perf tools: Fix strbuf_addf() when the buffer needs to grow
  perf header: Fix numa topology printing
  perf, powerpc: Fix hw breakpoints returning -ENOSPC
      455e987c
  3. 01 12月, 2012 20 次提交
  5. 30 11月, 2012 5 次提交
  7. 29 11月, 2012 9 次提交