The patch titled Subject: watchdog: don't run proc_watchdog_update if new value is same as old has been removed from the -mm tree. Its filename was watchdog-dont-run-proc_watchdog_update-if-new-value-is-same-as-old.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Joshua Hunt <johunt@xxxxxxxxxx> Subject: watchdog: don't run proc_watchdog_update if new value is same as old 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(). [ 955.756196] NMI watchdog: enabled on all CPUs, permanently consumes one hw-PMU counter. [ 955.765994] NMI watchdog: enabled on all CPUs, permanently consumes one hw-PMU counter. [ 955.774619] NMI watchdog: enabled on all CPUs, permanently consumes one hw-PMU counter. [ 955.783182] 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> Cc: <stable@xxxxxxxxxxxxxxx> [4.1.x+] Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- kernel/watchdog.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff -puN kernel/watchdog.c~watchdog-dont-run-proc_watchdog_update-if-new-value-is-same-as-old kernel/watchdog.c --- a/kernel/watchdog.c~watchdog-dont-run-proc_watchdog_update-if-new-value-is-same-as-old +++ a/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) { _ Patches currently in -mm which might be from johunt@xxxxxxxxxx are block-restore-proc-partitions-to-not-display-non-partitionable-removable-devices.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html