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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: 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>
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@ -520,13 +520,15 @@ int proc_dowatchdog(struct ctl_table *table, int write,
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void __user *buffer, size_t *lenp, loff_t *ppos)
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{
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int err, old_thresh, old_enabled;
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static DEFINE_MUTEX(watchdog_proc_mutex);
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mutex_lock(&watchdog_proc_mutex);
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old_thresh = ACCESS_ONCE(watchdog_thresh);
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old_enabled = ACCESS_ONCE(watchdog_user_enabled);
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err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
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if (err || !write)
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return err;
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goto out;
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set_sample_period();
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/*
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@ -544,7 +546,8 @@ int proc_dowatchdog(struct ctl_table *table, int write,
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watchdog_thresh = old_thresh;
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watchdog_user_enabled = old_enabled;
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}
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out:
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mutex_unlock(&watchdog_proc_mutex);
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return err;
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}
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#endif /* CONFIG_SYSCTL */
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