4.2.8-ckt7 -stable review patch. If anyone has any objections, please let me know.
---8<------------------------------------------------------------ From: Joshua Hunt <[email protected]> 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 <[email protected]> Acked-by: Don Zickus <[email protected]> Reviewed-by: Aaron Tomlin <[email protected]> Cc: Ulrich Obergfell <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Kamal Mostafa <[email protected]> --- 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
