user/sven/linux.git/kernel/hung_task.c, branch v3.0.51

hung_task: fix false positive during vfork

2012-01-06T22:14:13Z

commit f9fab10bbd768b0e5254e53a4a8477a94bfc4b96 upstream. 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 Reported-by: Sasha Levin LKML-Reference: <1325344394.28904.43.camel@lappy> Cc: Linus Torvalds Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Andrew Morton Cc: John Kacur Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

watchdog, hung_task_timeout: Add Kconfig configurable default

2011-04-28T07:13:17Z

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 e162b39a may have accidentally reverted commit fb822db4, which raised the default from 120 seconds to 480 seconds. Signed-off-by: Jeff Mahoney Acked-by: Mandeep Singh Baines Link: http://lkml.kernel.org/r/4DB8600C.8080000@suse.com Signed-off-by: Ingo Molnar

lockup detector: Fix grammar by adding a missing "to" in the comments

2010-08-17T07:11:52Z

This fixes a minor grammar problem in the comments in hung_task.c Signed-off-by: John Kacur Cc: Peter Zijlstra LKML-Reference: <1281021054-4228-2-git-send-email-jkacur@redhat.com> Signed-off-by: Ingo Molnar

lockdep: Remove __debug_show_held_locks

2010-08-17T07:11:10Z

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 Cc: Peter Zijlstra LKML-Reference: <1281021054-4228-1-git-send-email-jkacur@redhat.com> Signed-off-by: Ingo Molnar

softlockup: Fix hung_task_check_count sysctl

2009-11-27T05:21:57Z

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 Acked-by: Frederic Weisbecker Cc: msb@google.com LKML-Reference: <20091127022820.GU32182@kryten> Signed-off-by: Ingo Molnar

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

2009-09-24T14:21:04Z

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 Cc: David Howells Cc: "Eric W. Biederman" Cc: Al Viro Cc: Ralf Baechle Cc: Martin Schwidefsky Cc: Ingo Molnar Cc: "David S. Miller" Cc: James Morris Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

softlockup: ensure the task has been switched out once

2009-02-11T10:04:16Z

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 Acked-by: Mandeep Singh Baines Signed-off-by: Ingo Molnar

softlockup: remove timestamp checking from hung_task

2009-02-09T10:03:49Z

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 Signed-off-by: Ingo Molnar

softlockup: convert read_lock in hung_task to rcu_read_lock

2009-02-05T18:55:31Z

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 Signed-off-by: Mandeep Singh Baines Signed-off-by: Ingo Molnar

softlockup: check all tasks in hung_task

2009-02-05T18:54:57Z

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 Suggested-by: Frédéric Weisbecker Acked-by: Andrew Morton Signed-off-by: Ingo Molnar