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Commits on Jan 4, 2012
  1. @torvalds

    hung_task: fix false positive during vfork

    Mandeep Singh Baines authored torvalds committed
    vfork parent uninterruptibly and unkillably waits for its child to
    exec/exit. This wait is of unbounded length. Ignore such waits
    in the hung_task detector.
    
    Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
    Reported-by: Sasha Levin <levinsasha928@gmail.com>
    LKML-Reference: <1325344394.28904.43.camel@lappy>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: John Kacur <jkacur@redhat.com>
    Cc: stable@kernel.org
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commits on Oct 31, 2011
  1. kernel: Map most files to use export.h instead of module.h

    Paul Gortmaker authored
    The changed files were only including linux/module.h for the
    EXPORT_SYMBOL infrastructure, and nothing else.  Revector them
    onto the isolated export header for faster compile times.
    
    Nothing to see here but a whole lot of instances of:
    
      -#include <linux/module.h>
      +#include <linux/export.h>
    
    This commit is only changing the kernel dir; next targets
    will probably be mm, fs, the arch dirs, etc.
    
    Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Commits on Apr 28, 2011
  1. @jeffmahoney

    watchdog, hung_task_timeout: Add Kconfig configurable default

    jeffmahoney authored Ingo Molnar committed
    This patch allows the default value for sysctl_hung_task_timeout_secs
    to be set at build time. The feature carries virtually no overhead,
    so it makes sense to keep it enabled. On heavily loaded systems, though,
    it can end up triggering stack traces when there is no bug other than
    the system being underprovisioned. We use this patch to keep the hung task
    facility available but disabled at boot-time.
    
    The default of 120 seconds is preserved. As a note, commit e162b39 may
    have accidentally reverted commit fb822db, which raised the default from
    120 seconds to 480 seconds.
    
    Signed-off-by: Jeff Mahoney <jeffm@suse.com>
    Acked-by: Mandeep Singh Baines <msb@google.com>
    Link: http://lkml.kernel.org/r/4DB8600C.8080000@suse.com
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
Commits on Aug 17, 2010
  1. lockup detector: Fix grammar by adding a missing "to" in the comments

    John Kacur authored Ingo Molnar committed
    This fixes a minor grammar problem in the comments in
    hung_task.c
    
    Signed-off-by: John Kacur <jkacur@redhat.com>
    Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
    LKML-Reference: <1281021054-4228-2-git-send-email-jkacur@redhat.com>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
  2. lockdep: Remove __debug_show_held_locks

    John Kacur authored Ingo Molnar committed
    There is no longer any functional difference between
    __debug_show_held_locks() and debug_show_held_locks(),
    so remove the former.
    
    Signed-off-by: John Kacur <jkacur@redhat.com>
    Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
    LKML-Reference: <1281021054-4228-1-git-send-email-jkacur@redhat.com>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
Commits on Nov 27, 2009
  1. @antonblanchard

    softlockup: Fix hung_task_check_count sysctl

    antonblanchard authored Ingo Molnar committed
    I'm seeing spikes of up to 0.5ms in khungtaskd on a large
    machine. To reduce this source of jitter I tried setting
    hung_task_check_count to 0:
    
     # echo 0 > /proc/sys/kernel/hung_task_check_count
    
    which didn't have the intended response. Change to a post
    increment of max_count, so a value of 0 means check 0 tasks.
    
    Signed-off-by: Anton Blanchard <anton@samba.org>
    Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: msb@google.com
    LKML-Reference: <20091127022820.GU32182@kryten>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
Commits on Sep 24, 2009
  1. @torvalds

    sysctl: remove "struct file *" argument of ->proc_handler

    Alexey Dobriyan authored torvalds committed
    It's unused.
    
    It isn't needed -- read or write flag is already passed and sysctl
    shouldn't care about the rest.
    
    It _was_ used in two places at arch/frv for some reason.
    
    Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
    Cc: David Howells <dhowells@redhat.com>
    Cc: "Eric W. Biederman" <ebiederm@xmission.com>
    Cc: Al Viro <viro@zeniv.linux.org.uk>
    Cc: Ralf Baechle <ralf@linux-mips.org>
    Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: "David S. Miller" <davem@davemloft.net>
    Cc: James Morris <jmorris@namei.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commits on Feb 11, 2009
  1. @fweisbec

    softlockup: ensure the task has been switched out once

    fweisbec authored Ingo Molnar committed
    When we check if a task has been switched out since the last scan, we might
    have a race condition on the following scenario:
    
    - the task is freshly created and scheduled
    
    - it puts its state to TASK_UNINTERRUPTIBLE and is not yet switched out
    
    - check_hung_task() scans this task and will report a false positive because
      t->nvcsw + t->nivcsw == t->last_switch_count == 0
    
    Add a check for such cases.
    
    Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
    Acked-by: Mandeep Singh Baines <msb@google.com>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
Commits on Feb 9, 2009
  1. softlockup: remove timestamp checking from hung_task

    Mandeep Singh Baines authored Ingo Molnar committed
    Impact: saves sizeof(long) bytes per task_struct
    
    By guaranteeing that sysctl_hung_task_timeout_secs have elapsed between
    tasklist scans we can avoid using timestamps.
    
    Signed-off-by: Mandeep Singh Baines <msb@google.com>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
Commits on Feb 5, 2009
  1. softlockup: convert read_lock in hung_task to rcu_read_lock

    Mandeep Singh Baines authored Ingo Molnar committed
    Since the tasklist is protected by rcu list operations, it is safe
    to convert the read_lock()s to rcu_read_lock().
    
    Suggested-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Signed-off-by: Mandeep Singh Baines <msb@google.com>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
  2. softlockup: check all tasks in hung_task

    Mandeep Singh Baines authored Ingo Molnar committed
    Impact: extend the scope of hung-task checks
    
    Changed the default value of hung_task_check_count to PID_MAX_LIMIT.
    hung_task_batch_count added to put an upper bound on the critical
    section. Every hung_task_batch_count checks, the rcu lock is never
    held for a too long time.
    
    Keeping the critical section small minimizes time preemption is disabled
    and keeps rcu grace periods small.
    
    To prevent following a stale pointer, get_task_struct is called on g and t.
    To verify that g and t have not been unhashed while outside the critical
    section, the task states are checked.
    
    The design was proposed by Frédéric Weisbecker.
    
    Signed-off-by: Mandeep Singh Baines <msb@google.com>
    Suggested-by: Frédéric Weisbecker <fweisbec@gmail.com>
    Acked-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
Commits on Jan 18, 2009
  1. softlockup: fix potential race in hung_task when resetting timeout

    Mandeep Singh Baines authored Ingo Molnar committed
    Impact: fix potential false panic
    
    A potential race exists if sysctl_hung_task_timeout_secs is reset to 0
    while inside check_hung_uniterruptible_tasks(). If check_task() is
    entered, a comparison with 0 will result in a false hung_task being
    detected.
    
    If sysctl_hung_task_panic is set, the system will panic.
    
    Signed-off-by: Mandeep Singh Baines <msb@google.com>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
Commits on Jan 16, 2009
  1. softlockup: decouple hung tasks check from softlockup detection

    Mandeep Singh Baines authored Ingo Molnar committed
    Decoupling allows:
    
    * hung tasks check to happen at very low priority
    
    * hung tasks check and softlockup to be enabled/disabled independently
      at compile and/or run-time
    
    * individual panic settings to be enabled disabled independently
      at compile and/or run-time
    
    * softlockup threshold to be reduced without increasing hung tasks
      poll frequency (hung task check is expensive relative to softlock watchdog)
    
    * hung task check to be zero over-head when disabled at run-time
    
    Signed-off-by: Mandeep Singh Baines <msb@google.com>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
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