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Groups > linux.kernel > #1261584

[PATCH 3/4] watchdog: remove {get|put}_online_cpus() from watchdog_{park|unpark}_threads()

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watchdog_{park|unpark}_threads() are now called in code paths that
protect themselves against CPU hotplug, so {get|put}_online_cpus()
calls are redundant and can be removed.

Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
---
 kernel/watchdog.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 13fdda1..84c4744 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -683,33 +683,35 @@ static struct smp_hotplug_thread watchdog_threads = {
  * be parked and the watchdog threads of other CPUs can still be runnable.
  * Callers are expected to handle this special condition as appropriate in
  * their context.
+ *
+ * This function may only be called in a context that is protected against
+ * races with CPU hotplug - for example, via get_online_cpus().
  */
 static int watchdog_park_threads(void)
 {
 	int cpu, ret = 0;
 
-	get_online_cpus();
 	for_each_watchdog_cpu(cpu) {
 		ret = kthread_park(per_cpu(softlockup_watchdog, cpu));
 		if (ret)
 			break;
 	}
-	put_online_cpus();
 
 	return ret;
 }
 
 /*
  * unpark all watchdog threads that are specified in 'watchdog_cpumask'
+ *
+ * This function may only be called in a context that is protected against
+ * races with CPU hotplug - for example, via get_online_cpus().
  */
 static void watchdog_unpark_threads(void)
 {
 	int cpu;
 
-	get_online_cpus();
 	for_each_watchdog_cpu(cpu)
 		kthread_unpark(per_cpu(softlockup_watchdog, cpu));
-	put_online_cpus();
 }
 
 /*
-- 
1.7.11.7

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Thread

[PATCH 0/4] watchdog: address various races (CPU hotplug, timer expiry) Ulrich Obergfell <uobergfe@redhat.com> - 2015-11-03 16:20 +0100
  [PATCH 3/4] watchdog: remove {get|put}_online_cpus() from watchdog_{park|unpark}_threads() Ulrich Obergfell <uobergfe@redhat.com> - 2015-11-03 16:20 +0100
  [PATCH 2/4] watchdog: avoid races between /proc handlers and CPU hotplug Ulrich Obergfell <uobergfe@redhat.com> - 2015-11-03 16:20 +0100
  [PATCH 1/4] watchdog: avoid race between lockup detector suspend/resume and CPU hotplug Ulrich Obergfell <uobergfe@redhat.com> - 2015-11-03 17:20 +0100
  Re: [PATCH 0/4] watchdog: address various races (CPU hotplug, timer  expiry) Don Zickus <dzickus@redhat.com> - 2015-11-05 15:50 +0100
  Re: [PATCH 0/4] watchdog: address various races (CPU hotplug, timer  expiry) Aaron Tomlin <atomlin@redhat.com> - 2015-11-05 22:00 +0100

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