lkml.org 
[lkml]   [2016]   [Apr]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 4.5 142/238] watchdog: dont run proc_watchdog_update if new value is same as old
Date
4.5-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Joshua Hunt <johunt@akamai.com>

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@akamai.com>
Acked-by: Don Zickus <dzickus@redhat.com>
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
kernel/watchdog.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -923,6 +923,9 @@ static int proc_watchdog_common(int whic
* both lockup detectors are disabled if proc_watchdog_update()
* returns an error.
*/
+ if (old == new)
+ goto out;
+
err = proc_watchdog_update();
}
out:
@@ -967,7 +970,7 @@ int proc_soft_watchdog(struct ctl_table
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;

get_online_cpus();
mutex_lock(&watchdog_proc_mutex);
@@ -987,6 +990,10 @@ int proc_watchdog_thresh(struct ctl_tabl
/*
* Update the sample period. Restore on failure.
*/
+ new = ACCESS_ONCE(watchdog_thresh);
+ if (old == new)
+ goto out;
+
set_sample_period();
err = proc_watchdog_update();
if (err) {

\
 
 \ /
  Last update: 2016-04-10 22:41    [W:0.834 / U:0.120 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site