linux-kernel - Re: WARN_ON_ONCE() hit at kernel/events/core.c:330

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Date:   Mon, 8 Apr 2019 10:47:35 +0200
From:   Thomas-Mich Richter <tmricht@...ux.ibm.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Kees Cook <keescook@...omium.org>, acme@...hat.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Hendrik Brueckner <brueckner@...ux.ibm.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: WARN_ON_ONCE() hit at kernel/events/core.c:330

On 4/8/19 10:22 AM, Peter Zijlstra wrote:
> On Mon, Apr 08, 2019 at 09:12:28AM +0200, Thomas-Mich Richter wrote:
>>> Does the below cure things? It's not exactly pretty, but it could just
>>> do the trick.
>>>
>>> ---
>>> diff --git a/kernel/events/core.c b/kernel/events/core.c
>>> index dfc4bab0b02b..d496e6911442 100644
>>> --- a/kernel/events/core.c
>>> +++ b/kernel/events/core.c
>>> @@ -2009,8 +2009,8 @@ event_sched_out(struct perf_event *event,
>>>  	event->pmu->del(event, 0);
>>>  	event->oncpu = -1;
>>>  
>>> -	if (event->pending_disable) {
>>> -		event->pending_disable = 0;
>>> +	if (event->pending_disable == smp_processor_id()) {
>>> +		event->pending_disable = -1;
>>>  		state = PERF_EVENT_STATE_OFF;
>>>  	}
>>>  	perf_event_set_state(event, state);
>>> @@ -2198,7 +2198,7 @@ EXPORT_SYMBOL_GPL(perf_event_disable);
>>>  
>>>  void perf_event_disable_inatomic(struct perf_event *event)
>>>  {
>>> -	event->pending_disable = 1;
>>> +	event->pending_disable = smp_processor_id();
>>>  	irq_work_queue(&event->pending);
>>>  }
>>>  
>>> @@ -5822,8 +5822,8 @@ static void perf_pending_event(struct irq_work *entry)
>>>  	 * and we won't recurse 'further'.
>>>  	 */
>>>  
>>> -	if (event->pending_disable) {
>>> -		event->pending_disable = 0;
>>> +	if (event->pending_disable == smp_processor_id()) {
>>> +		event->pending_disable = -1;
>>>  		perf_event_disable_local(event);
>>>  	}
>>>  
>>> @@ -10236,6 +10236,7 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
>>>  
>>>  
>>>  	init_waitqueue_head(&event->waitq);
>>> +	event->pending_disable = -1;
>>>  	init_irq_work(&event->pending, perf_pending_event);
>>>  
>>>  	mutex_init(&event->mmap_mutex);
>>>
>>
>> Peter,
>>
>> very good news, your fix ran over the weekend without any hit!!!
>>
>> Thanks very much for your help. Do you submit this patch to the kernel mailing list?
> 
> Most excellent, let me go write a Changelog.
> 
> Could I convince you to implement arch_irq_work_raise() for s390?
> 

Yes, I am convinced, however I need to discuss this with the s390 maintainers
Martin Schwidesfky and Heiko Carstens first.

-- 
Thomas Richter, Dept 3252, IBM s390 Linux Development, Boeblingen, Germany
--
Vorsitzender des Aufsichtsrats: Matthias Hartmann
Geschäftsführung: Dirk Wittkopp
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