Messages in this thread Patch in this message | | | Date | Mon, 14 Mar 2016 12:29:55 -0400 | From | Don Zickus <> | Subject | Re: [PATCH] watchdog: don't run proc_watchdog_update if new value is same as old |
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On Mon, Mar 14, 2016 at 09:45:26AM -0500, Josh Hunt wrote: > On 03/14/2016 09:34 AM, Don Zickus wrote: > >On Sat, Mar 12, 2016 at 06:50:26PM -0500, Joshua Hunt wrote: > >>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(). Not only that, but when I > >>wrote to these proc files in a loop I could easily trigger a soft lockup. > >> > >>[ 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. > >>[ 959.788319] NMI watchdog: BUG: soft lockup - CPU#4 stuck for 30s! [swapper/4:0] > >>[ 959.788325] NMI watchdog: BUG: soft lockup - CPU#5 stuck for 30s! [swapper/5:0] > >> > >>There doesn't appear to be a reason for doing this work other every time a > >>write occurs, so only do the work when the values change. > > > >Hi Josh, > > > >Thanks for the patch. I have no objections to it, but Uli and myself were > >interested in the reason for the softlockups. Uli is going to provide a > >test patch to see if his theory is correct. That way we fix the underlying > >issue and then apply your patch on top. Make sense? > > Yep. Sounds good. I meant to mention I didn't diagnose the soft-lockup. If > you provide a patch I'm happy to test. I can also attempt to debug that part > more if needed.
Hi Josh,
I believe Uli thought the below patch might fix it.
Cheers, Don
diff --git a/kernel/watchdog.c b/kernel/watchdog.c index b3ace6e..dd298d2 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -517,12 +517,12 @@ static void watchdog_enable(unsigned int cpu) /* Enable the perf event */ watchdog_nmi_enable(cpu); + watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1); /* done here because hrtimer_start can only pin to smp_processor_id() */ hrtimer_start(hrtimer, ns_to_ktime(sample_period), HRTIMER_MODE_REL_PINNED); /* initialize timestamp */ - watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1); __touch_watchdog(); } @@ -530,8 +530,8 @@ static void watchdog_disable(unsigned int cpu) { struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer); - watchdog_set_prio(SCHED_NORMAL, 0); hrtimer_cancel(hrtimer); + watchdog_set_prio(SCHED_NORMAL, 0); /* disable the perf event */ watchdog_nmi_disable(cpu); }
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