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authorDon Zickus <dzickus@redhat.com>2017-01-25 02:17:53 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2017-01-25 03:26:14 +0300
commitb94f51183b0617e7b9b4fb4137d4cf1cab7547c2 (patch)
tree414e522ca20e4fcc2fcb0f2f987454d21a08a839 /include
parent6affb9d7b137fc93d86c926a5587e77b8bc64255 (diff)
downloadlinux-b94f51183b0617e7b9b4fb4137d4cf1cab7547c2.tar.xz
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>
Diffstat (limited to 'include')
-rw-r--r--include/linux/nmi.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/nmi.h b/include/linux/nmi.h
index aacca824a6ae..0a3fadc32693 100644
--- a/include/linux/nmi.h
+++ b/include/linux/nmi.h
@@ -110,6 +110,7 @@ extern int watchdog_user_enabled;
extern int watchdog_thresh;
extern unsigned long watchdog_enabled;
extern unsigned long *watchdog_cpumask_bits;
+extern atomic_t watchdog_park_in_progress;
#ifdef CONFIG_SMP
extern int sysctl_softlockup_all_cpu_backtrace;
extern int sysctl_hardlockup_all_cpu_backtrace;