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authorUlrich Obergfell <uobergfe@redhat.com>2015-11-05 18:44:47 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2015-11-05 19:34:48 -0800
commitee89e71eb091d3ef8ca2be8bd4ec77ccfa91334c (patch)
tree27ad57517e385733fb6ef9e52ef012d77e9ba623
parentac1f591249d95372f3a5ab3828d4af5dfbf5efd3 (diff)
kernel/watchdog.c: avoid race between lockup detector suspend/resume and CPU hotplug
The lockup detector suspend/resume interface that was introduced by commit 8c073d27d7ad ("watchdog: introduce watchdog_suspend() and watchdog_resume()") does not protect itself against races with CPU hotplug. Hence, theoretically it is possible that a new watchdog thread is started on a hotplugged CPU while the lockup detector is suspended, and the thread could thus interfere unexpectedly with the code that requested to suspend the lockup detector. Avoid the race by calling get_online_cpus() in lockup_detector_suspend() put_online_cpus() in lockup_detector_resume() Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com> Acked-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>
-rw-r--r--kernel/watchdog.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 0a23125369f1..7357842da933 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -719,6 +719,7 @@ int lockup_detector_suspend(void)
{
int ret = 0;
+ get_online_cpus();
mutex_lock(&watchdog_proc_mutex);
/*
* Multiple suspend requests can be active in parallel (counted by
@@ -759,6 +760,7 @@ void lockup_detector_resume(void)
watchdog_unpark_threads();
mutex_unlock(&watchdog_proc_mutex);
+ put_online_cpus();
}
static int update_watchdog_all_cpus(void)