Re: [PATCH v6 09/11] drm/i915/perf: allow holding preemption on filtered ctx

[Lionel Landwerlin <lionel.g.landwerlin@intel.com>]

On 01/07/2019 15:03, Chris Wilson wrote:
> Quoting Lionel Landwerlin (2019-07-01 12:34:35)
>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
>> index f92bace9caff..012d6d7f54e2 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
>> @@ -2104,6 +2104,14 @@ static int eb_oa_config(struct i915_execbuffer *eb)
>>          if (err)
>>                  return err;
>>   
>> +       /*
>> +        * If the perf stream was opened with hold preemption, flag the
>> +        * request properly so that the priority of the request is bumped once
>> +        * it reaches the execlist ports.
>> +        */
>> +       if (eb->i915->perf.oa.exclusive_stream->hold_preemption)
>> +               eb->request->flags |= I915_REQUEST_FLAGS_PERF;
> Just to reassure myself that this is the behaviour you:
>
> If the exclusive_stream is changed before the request is executed, it is
> likely that we no longer notice the earlier preemption-protection. This
> should not matter because the listener is no longer interested in those
> events?
> -Chris
>

Yeah, dropping the perf stream before your queries complete and you're 
in undefined behavior territory.


-Lionel

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