tjh.dev / kernel
Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel os linux
1
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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: 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>

authored by

Mandeep Singh Baines and committed by
Linus Torvalds f9fab10b 30e05324

+10 -4
+10 -4
kernel/hung_task.c
··· 74 74 75 75 /* 76 76 * Ensure the task is not frozen. 77 - * Also, when a freshly created task is scheduled once, changes 78 - * its state to TASK_UNINTERRUPTIBLE without having ever been 79 - * switched out once, it musn't be checked. 77 + * Also, skip vfork and any other user process that freezer should skip. 80 78 */ 81 - if (unlikely(t->flags & PF_FROZEN || !switch_count)) 79 + if (unlikely(t->flags & (PF_FROZEN | PF_FREEZER_SKIP))) 80 + return; 81 + 82 + /* 83 + * When a freshly created task is scheduled once, changes its state to 84 + * TASK_UNINTERRUPTIBLE without having ever been switched out once, it 85 + * musn't be checked. 86 + */ 87 + if (unlikely(!switch_count)) 82 88 return; 83 89 84 90 if (switch_count != t->last_switch_count) {