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From: Ulrich Obergfell <uobergfe@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: akpm@linux-foundation.org, dzickus@redhat.com,
	atomlin@redhat.com, uobergfe@redhat.com
Subject: [PATCH 3/4] watchdog: remove {get|put}_online_cpus() from watchdog_{park|unpark}_threads()
Date: Tue,  3 Nov 2015 16:21:00 +0100	[thread overview]
Message-ID: <1446564061-3379-4-git-send-email-uobergfe@redhat.com> (raw)
In-Reply-To: <1446564061-3379-1-git-send-email-uobergfe@redhat.com>

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


  parent reply	other threads:[~2015-11-03 15:17 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-11-03 15:20 [PATCH 0/4] watchdog: address various races (CPU hotplug, timer expiry) Ulrich Obergfell
2015-11-03 15:20 ` [PATCH 1/4] watchdog: avoid race between lockup detector suspend/resume and CPU hotplug Ulrich Obergfell
2015-11-03 15:20 ` [PATCH 2/4] watchdog: avoid races between /proc handlers " Ulrich Obergfell
2015-11-03 15:21 ` Ulrich Obergfell [this message]
2015-11-03 15:21 ` [PATCH 4/4] watchdog: fix race between proc_watchdog_thresh() and watchdog_timer_fn() Ulrich Obergfell
2015-11-05 14:46 ` [PATCH 0/4] watchdog: address various races (CPU hotplug, timer expiry) Don Zickus
2015-11-05 20:50 ` Aaron Tomlin

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