softlockup: make detector be aware of task switch of processes hogging cpu

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For now, soft lockup detector warns once for each case of process
softlockup.  But the thread 'watchdog/n' may not always get the cpu at the
time slot between the task switch of two processes hogging that cpu to
reset soft_watchdog_warn.

An example would be two processes hogging the cpu.  Process A causes the
softlockup warning and is killed manually by a user.  Process B
immediately becomes the new process hogging the cpu preventing the
softlockup code from resetting the soft_watchdog_warn variable.

This case is a false negative of "warn only once for a process", as there
may be a different process that is going to hog the cpu.  Resolve this by
saving/checking the task pointer of the hogging process and use that to
reset soft_watchdog_warn too.

[dzickus@redhat.com: update comment]
Signed-off-by: chai wen <chaiw.fnst@cn.fujitsu.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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chai wen 2014-10-09 15:25:17 -07:00 • committed by Linus Torvalds

parent f775da2fc2

commit b1a8de1f53

1 changed files with 17 additions and 1 deletions

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kernel/watchdog.c

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