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Commit 359e6fab authored by Michal Hocko's avatar Michal Hocko Committed by Linus Torvalds
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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: default avatarMichal Hocko <mhocko@suse.cz>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: default avatarDon Zickus <dzickus@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus 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 */