Commit 359e6fab authored Sep 24, 2013 by Michal Hocko Committed by Linus Torvalds Sep 24, 2013

watchdog: update watchdog attributes atomically



proc_dowatchdog doesn't synchronize multiple callers which might lead to
confusion when two parallel callers might confuse watchdog_enable_all_cpus
resp watchdog_disable_all_cpus (eg watchdog gets enabled even if
watchdog_thresh was set to 0 already).

This patch adds a local mutex which synchronizes callers to the sysctl
handler.

Signed-off-by: Michal Hocko <mhocko@suse.cz>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Don Zickus <dzickus@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 4a10c2ac

kernel/watchdog.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -520,13 +520,15 @@ int proc_dowatchdog(struct ctl_table *table, int write,
		void __user buffer, size_t lenp, loff_t *ppos)
		{
		int err, old_thresh, old_enabled;
		static DEFINE_MUTEX(watchdog_proc_mutex);

		mutex_lock(&watchdog_proc_mutex);
		old_thresh = ACCESS_ONCE(watchdog_thresh);
		old_enabled = ACCESS_ONCE(watchdog_user_enabled);

		err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
		if (err \|\| !write)
		return err;
		goto out;

		set_sample_period();
		/*
		@@ -544,7 +546,8 @@ int proc_dowatchdog(struct ctl_table *table, int write,
		watchdog_thresh = old_thresh;
		watchdog_user_enabled = old_enabled;
		}

		out:
		mutex_unlock(&watchdog_proc_mutex);
		return err;
		}
		#endif /* CONFIG_SYSCTL */

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