[Intel-gfx] [PATCH v7 09/12] drm/i915: add a new perf configuration execbuf parameter

[Lionel Landwerlin]

On 09/07/2019 14:06, Chris Wilson wrote:
> Quoting Lionel Landwerlin (2019-07-09 11:59:31)
>> On 09/07/2019 12:58, Chris Wilson wrote:
>>> Quoting Lionel Landwerlin (2019-07-09 10:32:05)
>>>> +static int eb_oa_config(struct i915_execbuffer *eb)
>>>> +{
>>>> +       int err;
>>>> +
>>>> +       if (!eb->oa_config)
>>>> +               return 0;
>>>> +
>>>> +       err = i915_active_request_set(&eb->engine->last_oa_config,
>>>> +                                     eb->request);
>>> This is outside of the eb->request->timeline->mutex and needs a mutex.
>>
>> Can I do this inside i915_request_add() when rq->flags &
>> I915_REQUEST_FLAGS_PERF ?
> No. Because it is still being accessed without the appropriate locks.
> (Multiple callers trying to modify eb->engine->last_oa_config all using
> their own timeline->mutex.) You already need a lock to serialise
> oa_config, that seems adequate to cover last_oa_config as well.
>
> Oh, don't call the flag _PERF but something like FLAGS_NOPREEMPT so
> it indicates the mechanism. Come to think of this don't include _FLAGS_
> as we don't need to disambiguate yet :)
> -Chris
>
Aligns perfectly ;)


-Lionel