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Groups > linux.kernel > #1671854
| From | Prarit Bhargava <prarit@redhat.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH V2] kernel/watchdog: fix spurious hard lockups |
| Date | 2017-06-21 19:50 +0200 |
| Message-ID | <tURVo-Rb-17@gated-at.bofh.it> (permalink) |
| References | <tUP7c-7m1-15@gated-at.bofh.it> <tUPAd-7N4-5@gated-at.bofh.it> <tURiH-zB-45@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On 06/21/2017 11:47 AM, Liang, Kan wrote:
>
>
>> On Wed, 21 Jun 2017, kan.liang@intel.com wrote:
>>>
>>> #ifdef CONFIG_HARDLOCKUP_DETECTOR
>>> +/*
>>> + * The NMI watchdog relies on PERF_COUNT_HW_CPU_CYCLES event,
>> which
>>> + * can tick faster than the measured CPU Frequency due to Turbo mode.
>>> + * That can lead to spurious timeouts.
>>> + * To workaround the issue, extending the period by 3 times.
>>> + */
>>> u64 hw_nmi_get_sample_period(int watchdog_thresh) {
>>> - return (u64)(cpu_khz) * 1000 * watchdog_thresh;
>>> + return (u64)(cpu_khz) * 1000 * watchdog_thresh * 3;
>>
>> The maximum turbo frequency of any given machine can be retrieved.
>
> The maximum turbo frequency is determined by the model of processor.
> I'm not sure if there is a generic way to get the maximum turbo frequency.
> Is there?
>
cpufreq_quick_get_max()
but iff cpufreq subsystem is initialized. O/w 0 is returned for the freq.
Quick test shows the correct turbo max of 3700000 on my 2000000 (2.00GHz)
system.
P.
> Thanks,
> Kan
>
>>
>> So why don't you simply take that ratio into account and apply it for the
>> machines which have those insane turbo loaders? That's not a huge effort,
>> can be easily backported and does not inflict this unconditially.
>>
>> So what you want is:
>>
>> return get_max_turbo_khz() * 1000 * watchdog_thresh;
>>
>> Where get_max_turbo_khz() by default returns cpu_khz for non turbo
>> motors.
>>
>> And instead of silently doing this it should emit a info into dmesg:
>>
>> u64 period, max_khz = get_max_turbo_khz();
>> static int once;
>>
>> period = max_khz * 1000 * watchdog_thresh;
>>
>> if (max_khz != cpu_khz && !once) {
>> unsigned int msec = period / cpu_khz;
>>
>> once = 1;
>> pr_info("Adjusted watchdog threshold to %u.%04u sec\n",
>> msec / 1000, msec % 1000);
>> }
>>
>> return period;
>>
>> Hmm?
>>
>> Thanks,
>>
>> tglx
>
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[PATCH V2] kernel/watchdog: fix spurious hard lockups kan.liang@intel.com - 2017-06-21 16:50 +0200
Re: [PATCH V2] kernel/watchdog: fix spurious hard lockups Thomas Gleixner <tglx@linutronix.de> - 2017-06-21 17:20 +0200
RE: [PATCH V2] kernel/watchdog: fix spurious hard lockups "Liang, Kan" <kan.liang@intel.com> - 2017-06-21 19:10 +0200
Re: [PATCH V2] kernel/watchdog: fix spurious hard lockups Prarit Bhargava <prarit@redhat.com> - 2017-06-21 19:50 +0200
Re: [PATCH V2] kernel/watchdog: fix spurious hard lockups Andi Kleen <ak@linux.intel.com> - 2017-06-21 19:10 +0200
Re: [PATCH V2] kernel/watchdog: fix spurious hard lockups Thomas Gleixner <tglx@linutronix.de> - 2017-06-21 22:10 +0200
Re: [PATCH V2] kernel/watchdog: fix spurious hard lockups Thomas Gleixner <tglx@linutronix.de> - 2017-06-22 00:00 +0200
Re: [PATCH V2] kernel/watchdog: fix spurious hard lockups Thomas Gleixner <tglx@linutronix.de> - 2017-06-22 17:40 +0200
Re: [PATCH V2] kernel/watchdog: fix spurious hard lockups Don Zickus <dzickus@redhat.com> - 2017-06-22 17:50 +0200
RE: [PATCH V2] kernel/watchdog: fix spurious hard lockups "Liang, Kan" <kan.liang@intel.com> - 2017-06-22 18:00 +0200
Re: [PATCH V2] kernel/watchdog: fix spurious hard lockups Thomas Gleixner <tglx@linutronix.de> - 2017-06-23 10:10 +0200
Re: [PATCH V2] kernel/watchdog: fix spurious hard lockups Don Zickus <dzickus@redhat.com> - 2017-06-23 18:30 +0200
Re: [PATCH V2] kernel/watchdog: fix spurious hard lockups Thomas Gleixner <tglx@linutronix.de> - 2017-06-24 00:00 +0200
Re: [PATCH V2] kernel/watchdog: fix spurious hard lockups Don Zickus <dzickus@redhat.com> - 2017-06-26 22:30 +0200
Re: [PATCH V2] kernel/watchdog: fix spurious hard lockups Thomas Gleixner <tglx@linutronix.de> - 2017-06-26 22:40 +0200
Re: [PATCH V2] kernel/watchdog: fix spurious hard lockups Don Zickus <dzickus@redhat.com> - 2017-06-27 22:20 +0200
RE: [PATCH V2] kernel/watchdog: fix spurious hard lockups "Liang, Kan" <kan.liang@intel.com> - 2017-06-27 22:50 +0200
Re: [PATCH V2] kernel/watchdog: fix spurious hard lockups Don Zickus <dzickus@redhat.com> - 2017-06-27 23:10 +0200
Re: [PATCH V2] kernel/watchdog: fix spurious hard lockups Andi Kleen <ak@linux.intel.com> - 2017-06-28 01:50 +0200
Re: [PATCH V2] kernel/watchdog: fix spurious hard lockups Don Zickus <dzickus@redhat.com> - 2017-06-28 21:10 +0200
Re: [PATCH V2] kernel/watchdog: fix spurious hard lockups Andi Kleen <ak@linux.intel.com> - 2017-06-28 22:20 +0200
Re: [PATCH V2] kernel/watchdog: fix spurious hard lockups Don Zickus <dzickus@redhat.com> - 2017-06-29 17:50 +0200
Re: [PATCH V2] kernel/watchdog: fix spurious hard lockups Andi Kleen <ak@linux.intel.com> - 2017-06-29 18:20 +0200
Re: [PATCH V2] kernel/watchdog: fix spurious hard lockups Don Zickus <dzickus@redhat.com> - 2017-06-29 18:30 +0200
Re: [PATCH V2] kernel/watchdog: fix spurious hard lockups Andi Kleen <ak@linux.intel.com> - 2017-06-29 18:40 +0200
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