linux-kernel - Re: System crash with perf

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Message-Id: <4e816b25-1763-ec23-0642-19e6258e6ac5@linux.ibm.com>
Date:   Fri, 1 Feb 2019 13:24:19 +0530
From:   Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-perf-users@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>, eranian@...gle.com,
        vincent.weaver@...ne.edu,
        "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Subject: Re: System crash with perf_fuzzer (kernel: 5.0.0-rc3)

Hi Jiri,

On 2/1/19 1:13 PM, Jiri Olsa wrote:
> On Thu, Jan 31, 2019 at 09:27:11AM +0100, Jiri Olsa wrote:
>> On Wed, Jan 30, 2019 at 07:36:48PM +0100, Jiri Olsa wrote:
>>
>> SNIP
>>
>>> diff --git a/kernel/events/core.c b/kernel/events/core.c
>>> index 280a72b3a553..22ec63a0782e 100644
>>> --- a/kernel/events/core.c
>>> +++ b/kernel/events/core.c
>>> @@ -4969,6 +4969,26 @@ static void __perf_event_period(struct perf_event *event,
>>>  	}
>>>  }
>>>  
>>> +static int check_period(struct perf_event *event, u64 value)
>>> +{
>>> +	u64 sample_period_attr = event->attr.sample_period;
>>> +	u64 sample_period_hw   = event->hw.sample_period;
>>> +	int ret;
>>> +
>>> +	if (event->attr.freq) {
>>> +		event->attr.sample_freq = value;
>>> +	} else {
>>> +		event->attr.sample_period = value;
>>> +		event->hw.sample_period = value;
>>> +	}
>>
>> hm, I think we need to check the period without changing the event,
>> because we don't disable pmu, so it might get picked up by bts code
>>
>> will check
> 
> with attached patch I did not trigger the fuzzer crash
> for over a day now, could you guys try?

I ran fuzzer for couple of hours but I didn't see any crash with
your previous patch.

I'll try this newer one as well.

Thanks.