Re: kselftest:lost_exception_test failure with 4.11.0-rc5

[Madhavan Srinivasan <maddy@linux.vnet.ibm.com>]

On Friday 07 April 2017 06:06 PM, Michael Ellerman wrote:
> Sachin Sant <sachinp@linux.vnet.ibm.com> writes:
>
>> I have run into few instances where the lost_exception_test from
>> powerpc kselftest fails with SIGABRT. Following o/p is against
>> 4.11.0-rc5. The failure is intermittent.
> What hardware are you on?
>
> How long does it take to run when it fails? I assume ~2 minutes?

Started a run in power8 host (habanero) and it is more than 24hrs and
havent failed yet. So this should be guest/VM scenario then?

>
>> When the test fails it is killed due to SIGABRT.
>> # ./lost_exception_test
>> test: lost_exception
>> tags: git_version:unknown
>> Binding to cpu 8
>> main test running as pid 9208
>> EBB Handler is at 0x10003dcc
>> !! killing lost_exception
> This is the parent (test harness saying) it's about to kill the child,
> because it took too long.
>
> It sends SIGTERM, but the child catches that, prints all this info, and
> then aborts() - so that's why you're seeing SIGABRT.
>
>> ebb_state):
>>    ebb_count    = 191529
> The test usually runs until it's taken 1,000,000 EBBs, so it looks like
> we got stuck.
>
>>    spurious     = 0
>>    negative     = 0
>>    no_overflow  = 0
>>    pmc[1] count = 0x0
>>    pmc[2] count = 0x0
>>    pmc[3] count = 0x0
>>    pmc[4] count = 0x4c1b707
> We use a varying sample period of between 400 and 600, and from above
> we've taken 191,529 EBBs.
>
> 0x4c1b707 / 191,529 ~= 416
>
> So that looks reasonable.
>
>>    pmc[5] count = 0x0
>>    pmc[6] count = 0x0
>> HW state:
>> MMCR0 0x0000000080000080 FC PMAO
> But this says we're stopped with counters frozen and an event pending.
>
>> MMCR2 0x0000000000000000
>> EBBHR 0x0000000010003dcc
>> BESCR 0x8000000100000000 GE PMAE
> And that says we have global enable set and events enabled.
>
>
> So I think there is a bug here somewhere. I don't really have time to
> dig into it now, neither does Maddy I think. But we should try and get
> to it at some point.
>
> cheers
>