4.2.8-ckt7 -stable review patch. If anyone has any objections, please let me know.
---8<------------------------------------------------------------
From: Joshua Hunt <johunt@xxxxxxxxxx>
commit a1ee1932aa6bea0bb074f5e3ced112664e4637ed 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: Josh Hunt <johunt@xxxxxxxxxx>
Acked-by: Don Zickus <dzickus@xxxxxxxxxx>
Reviewed-by: Aaron Tomlin <atomlin@xxxxxxxxxx>
Cc: Ulrich Obergfell <uobergfe@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
---
kernel/watchdog.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index a6ffa43..8389aaf 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -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.
* Restore 'watchdog_enabled' on failure.
*/
+ if (old == new)
+ goto out;
+
err = proc_watchdog_update();
if (err)
watchdog_enabled = old;
@@ -868,7 +871,7 @@ int proc_soft_watchdog(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)
{
- int err, old;
+ int err, old, new;
mutex_lock(&watchdog_proc_mutex);
@@ -882,6 +885,10 @@ int proc_watchdog_thresh(struct ctl_table *table, int write,
* Update the sample period.
* Restore 'watchdog_thresh' on failure.
*/
+ new = ACCESS_ONCE(watchdog_thresh);
+ if (old == new)
+ goto out;
+
set_sample_period();
err = proc_watchdog_update();
if (err)
--
2.7.4
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