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Subject: Re: [regression 4.14rc] 74def747bcd0 (genirq: Restrict effective
 affinity to interrupts actually using it)
To: Yanko Kaneti <yaneti@declera.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>
References: <1505833936.2634.11.camel@declera.com>
 <4374f6c0-dd67-3bd3-91a0-685eb9a0d711@arm.com>
 <1505835616.2634.14.camel@declera.com>
From: Marc Zyngier <marc.zyngier@arm.com>
Organization: ARM Ltd
Message-ID: <225dd0d8-2c27-57a6-c17d-c552c011d8da@arm.com>
Date: Tue, 19 Sep 2017 16:51:06 +0100
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On 19/09/17 16:40, Yanko Kaneti wrote:
> On Tue, 2017-09-19 at 16:33 +0100, Marc Zyngier wrote:
>> On 19/09/17 16:12, Yanko Kaneti wrote:
>>> Hello, 
>>>
>>> Fedora rawhide config here. 
>>> AMD FX-8370E
>>>
>>> Bisected a problem to:
>>> 74def747bcd0 (genirq: Restrict effective affinity to interrupts actually using it) 
>>>
>>> It seems to be causing stalls, short lived or long lived lockups very shortly after boot. 
>>> Everything becomes jerky.
>>>
>>> The only visible in the log indication is something like :
>>> ....
>>> [   59.802129] clocksource: timekeeping watchdog on CPU3: Marking clocksource 'tsc' as unstable because the skew is too large:
>>> [   59.802134] clocksource:                       'hpet' wd_now: 3326e7aa wd_last: 329956f8 mask: ffffffff
>>> [   59.802137] clocksource:                       'tsc' cs_now: 423662bc6f cs_last: 41dfc91650 mask: ffffffffffffffff
>>> [   59.802140] tsc: Marking TSC unstable due to clocksource watchdog
>>> [   59.802158] TSC found unstable after boot, most likely due to broken BIOS. Use 'tsc=unstable'.
>>> [   59.802161] sched_clock: Marking unstable (59802142067, 15510)<-(59920871789, -118714277)
>>> [   60.015604] clocksource: Switched to clocksource hpet
>>> [   89.015994] INFO: NMI handler (perf_event_nmi_handler) took too long to run: 209.660 msecs
>>> [   89.016003] perf: interrupt took too long (1638003 > 2500), lowering kernel.perf_event_max_sample_rate to 1000
>>> ....
>>>
>>> Just reverting that commit on top of linus mainline cures all the symptoms
>>
>> Interesting. Do you still get HPET interrupts?
> 
> Sorry, I might need some basic help here (i.e where do I count them...)

/proc/interrupts should display them.

> After the watchdog switches the clocksource to hpet the system is still
>  somewhat alive, so I'll guess some clock is still ticking....
Probably, but I suspect they're not hitting the right CPU, hence the
lockups.

Unfortunately, my x86-foo is pretty minimal, and I'm about to drop off
the net for a few days.

Thomas, any insight?

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...