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Commit f9fab10b authored by Mandeep Singh Baines's avatar Mandeep Singh Baines Committed by Linus Torvalds
Browse files

hung_task: fix false positive during vfork 



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: default avatarMandeep Singh Baines <msb@chromium.org>
Reported-by: default avatarSasha 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: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 30e05324

kernel/hung_task.c

+10 −4
Original line number Diff line number Diff line
@@ -74,11 +74,17 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout) 


	/*

	 * Ensure the task is not frozen.

	 * Also, when a freshly created task is scheduled once, changes

	 * its state to TASK_UNINTERRUPTIBLE without having ever been

	 * switched out once, it musn't be checked.

	 * Also, skip vfork and any other user process that freezer should skip.

	 */

	if (unlikely(t->flags & PF_FROZEN || !switch_count))

	if (unlikely(t->flags & (PF_FROZEN | PF_FREEZER_SKIP)))

	    return;



	/*

	 * When a freshly created task is scheduled once, changes its state to

	 * TASK_UNINTERRUPTIBLE without having ever been switched out once, it

	 * musn't be checked.

	 */

	if (unlikely(!switch_count))

		return;



	if (switch_count != t->last_switch_count) {