[Intel-gfx] [PATCH v10 3/4] drm/i915/perf: prepare driver to receive multiple ctx handles

[Lionel Landwerlin]

On 30/04/2020 17:55, Chris Wilson wrote:
> Quoting Lionel Landwerlin (2020-04-30 14:55:35)
>> @@ -1382,6 +1446,12 @@ static void i915_oa_stream_destroy(struct i915_perf_stream *stream)
>>   
>>          BUG_ON(stream != perf->exclusive_stream);
>>   
>> +       err = intel_context_pin(stream->config_context);
>> +       if (err) {
>> +               drm_err(&perf->i915->drm,
>> +                       "Error pinning i915-perf context\n");
>> +       }
> Reading through, this is the last thing that leapt out at me.
>
> Taking an error here would be nasty, and we do allow the pin to be
> interrupted (which would be a surprise for most people who call
> close()).
>
> The only suggestion I can make, is that the stream always keeps it
> pinned.
>
> >From the robustness point of view, it's better if we break
> stream->config_context than if we break stream->engine->kernel_context,
> but equally pinning another context image [about 80k in total] just for
> safety? Probably worth it. [If we break the kernel_context, we cannot do
> hang detection or pm/idle, the driver comes grinding to a halt.]
> -Chris

Yeah, I didn't like writing this error path there either.

-Lionel