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watchdog: update watchdog attributes atomically

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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>
This commit is contained in:
Michal Hocko 2013-09-24 15:27:29 -07:00 committed by Linus Torvalds
parent 4a10c2ac2f
commit 359e6fab66
1 changed files with 5 additions and 2 deletions
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7
kernel/watchdog.c
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@ -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 */