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authorDon Zickus <dzickus@redhat.com>2017-01-24 15:17:53 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-01-24 16:26:14 -0800
commitb94f51183b0617e7b9b4fb4137d4cf1cab7547c2 (patch)
tree414e522ca20e4fcc2fcb0f2f987454d21a08a839 /drivers/memstick/core
parent6affb9d7b137fc93d86c926a5587e77b8bc64255 (diff)
downloadlinux-b94f51183b0617e7b9b4fb4137d4cf1cab7547c2.tar.bz2
kernel/watchdog: prevent false hardlockup on overloaded system
On an overloaded system, it is possible that a change in the watchdog threshold can be delayed long enough to trigger a false positive. This can easily be achieved by having a cpu spinning indefinitely on a task, while another cpu updates watchdog threshold. What happens is while trying to park the watchdog threads, the hrtimers on the other cpus trigger and reprogram themselves with the new slower watchdog threshold. Meanwhile, the nmi watchdog is still programmed with the old faster threshold. Because the one cpu is blocked, it prevents the thread parking on the other cpus from completing, which is needed to shutdown the nmi watchdog and reprogram it correctly. As a result, a false positive from the nmi watchdog is reported. Fix this by setting a park_in_progress flag to block all lockups until the parking is complete. Fix provided by Ulrich Obergfell. [akpm@linux-foundation.org: s/park_in_progress/watchdog_park_in_progress/] Link: http://lkml.kernel.org/r/1481041033-192236-1-git-send-email-dzickus@redhat.com Signed-off-by: Don Zickus <dzickus@redhat.com> Reviewed-by: Aaron Tomlin <atomlin@redhat.com> Cc: Ulrich Obergfell <uobergfe@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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