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authorJoshua Hunt <johunt@akamai.com>2016-03-17 14:17:23 -0700
committerSasha Levin <sasha.levin@oracle.com>2016-04-18 08:51:01 -0400
commit15207f3ca364563c590ba170ce40c1f90fd78268 (patch)
treee7f181244f641f3b3628788f943e5a0cad0e3a31 /kernel
parent3ec245e8591a183e276df89cd7f9e7a15645b9da (diff)
watchdog: don't run proc_watchdog_update if new value is same as old
[ Upstream commit a1ee1932aa6bea0bb074f5e3ced112664e4637ed ] 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@akamai.com> Acked-by: Don Zickus <dzickus@redhat.com> Reviewed-by: Aaron Tomlin <atomlin@redhat.com> Cc: Ulrich Obergfell <uobergfe@redhat.com> Cc: <stable@vger.kernel.org> [4.1.x+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/watchdog.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 581a68a04c64..f89ea713213f 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -812,6 +812,9 @@ 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;
@@ -857,7 +860,7 @@ 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);
@@ -871,6 +874,10 @@ 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)