Commit ae76050c authored by Joshua Hunt's avatar Joshua Hunt Committed by Kamal Mostafa

watchdog: don't run proc_watchdog_update if new value is same as old

commit a1ee1932 upstream.

While working on a script to restore all sysctl params before a series of
tests I found that writing any value into the
/proc/sys/kernel/{nmi_watchdog,soft_watchdog,watchdog,watchdog_thresh}
causes them to call proc_watchdog_update().

  NMI watchdog: enabled on all CPUs, permanently consumes one hw-PMU counter.
  NMI watchdog: enabled on all CPUs, permanently consumes one hw-PMU counter.
  NMI watchdog: enabled on all CPUs, permanently consumes one hw-PMU counter.
  NMI watchdog: enabled on all CPUs, permanently consumes one hw-PMU counter.

There doesn't appear to be a reason for doing this work every time a write
occurs, so only do it when the values change.
Signed-off-by: default avatarJosh Hunt <johunt@akamai.com>
Acked-by: default avatarDon Zickus <dzickus@redhat.com>
Reviewed-by: default avatarAaron Tomlin <atomlin@redhat.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarKamal Mostafa <kamal@canonical.com>
parent 9fdae70d
...@@ -823,6 +823,9 @@ static int proc_watchdog_common(int which, struct ctl_table *table, int write, ...@@ -823,6 +823,9 @@ static int proc_watchdog_common(int which, struct ctl_table *table, int write,
* Update the run state of the lockup detectors. * Update the run state of the lockup detectors.
* Restore 'watchdog_enabled' on failure. * Restore 'watchdog_enabled' on failure.
*/ */
if (old == new)
goto out;
err = proc_watchdog_update(); err = proc_watchdog_update();
if (err) if (err)
watchdog_enabled = old; watchdog_enabled = old;
...@@ -868,7 +871,7 @@ int proc_soft_watchdog(struct ctl_table *table, int write, ...@@ -868,7 +871,7 @@ int proc_soft_watchdog(struct ctl_table *table, int write,
int proc_watchdog_thresh(struct ctl_table *table, int write, int proc_watchdog_thresh(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos) void __user *buffer, size_t *lenp, loff_t *ppos)
{ {
int err, old; int err, old, new;
mutex_lock(&watchdog_proc_mutex); mutex_lock(&watchdog_proc_mutex);
...@@ -882,6 +885,10 @@ int proc_watchdog_thresh(struct ctl_table *table, int write, ...@@ -882,6 +885,10 @@ int proc_watchdog_thresh(struct ctl_table *table, int write,
* Update the sample period. * Update the sample period.
* Restore 'watchdog_thresh' on failure. * Restore 'watchdog_thresh' on failure.
*/ */
new = ACCESS_ONCE(watchdog_thresh);
if (old == new)
goto out;
set_sample_period(); set_sample_period();
err = proc_watchdog_update(); err = proc_watchdog_update();
if (err) if (err)
......
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