linux-kernel - Re: [regression 4.14rc] 74def747bcd0 (genirq: Restrict effective affinity to interrupts actually using it)

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Date:   Sun, 1 Oct 2017 14:46:15 +0200
From:   Thorsten Leemhuis <regressions@...mhuis.info>
To:     Chuck Ebbert <cebbert.lkml@...il.com>,
        Marc Zyngier <marc.zyngier@....com>
Cc:     Yanko Kaneti <yaneti@...lera.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [regression 4.14rc] 74def747bcd0 (genirq: Restrict effective
 affinity to interrupts actually using it)

Hi, the regression tracker here. What's the status of this issue? Was
the problem fixed? It seems nothing happened for more than 10 days -- or
did the discussion move somewhere else? Ciao, Thorsten

On 20.09.2017 02:30, Chuck Ebbert wrote:
> On Tue, 19 Sep 2017 16:51:06 +0100
> Marc Zyngier <marc.zyngier@....com> wrote:
> 
>> 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?
> 
> Looking at flat_cpu_mask_to_apicid(), I don't see how 74def747bcd0
> can be correct:
> 
> 	struct cpumask *effmsk =
> 	irq_data_get_effective_affinity_mask(irqdata); unsigned long
> 	cpu_mask = cpumask_bits(mask)[0] & APIC_ALL_CPUS;
> 
> 	if (!cpu_mask)
> 		return -EINVAL;
> 	*apicid = (unsigned int)cpu_mask;
> 	cpumask_bits(effmsk)[0] = cpu_mask;
> 
> Before that patch, this function wrote to the effective mask
> unconditionally. After, it only writes to effective_mask if it is
> already non-zero.
> 
> 
> http://news.gmane.org/find-root.php?message_id=20170919203044.560cb9f1%40gmail.com 
> http://mid.gmane.org/20170919203044.560cb9f1%40gmail.com
>