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
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