[Intel-gfx] [PATCH] drm/i915: Tidy up GEM_TRACE around execlists

[Tvrtko Ursulin]

On 20/12/2017 12:43, Chris Wilson wrote:
> Quoting Tvrtko Ursulin (2017-12-20 12:39:42)
>>
>> On 20/12/2017 09:06, Chris Wilson wrote:
>>> Looking at the coordination of resets with the submission of execlists,
>>> it will be useful to have a GEM_TRACE for when we issue the reset.
>>> Whilst there tidy up the other GEM_TRACE to always include the engine
>>> name, and be careful not to trust any pointers prior to asserts.
>>>
>>> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
>>> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
>>> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
>>> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
>>> ---
>>>    drivers/gpu/drm/i915/intel_lrc.c | 6 ++++--
>>>    1 file changed, 4 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
>>> index 6205d320b86f..84029806cf3f 100644
>>> --- a/drivers/gpu/drm/i915/intel_lrc.c
>>> +++ b/drivers/gpu/drm/i915/intel_lrc.c
>>> @@ -504,7 +504,7 @@ static void inject_preempt_context(struct intel_engine_cs *engine)
>>>        ce->ring->tail &= (ce->ring->size - 1);
>>>        ce->lrc_reg_state[CTX_RING_TAIL+1] = ce->ring->tail;
>>>    
>>> -     GEM_TRACE("\n");
>>> +     GEM_TRACE("%s\n", engine->name);
>>>        for (n = execlists_num_ports(&engine->execlists); --n; )
>>>                elsp_write(0, engine->execlists.elsp);
>>>    
>>> @@ -906,7 +906,7 @@ static void execlists_submission_tasklet(unsigned long data)
>>>                        GEM_TRACE("%s out[0]: ctx=%d.%d, seqno=%x\n",
>>>                                  engine->name,
>>>                                  port->context_id, count,
>>> -                               rq->global_seqno);
>>> +                               rq ? rq->global_seqno : 0);
>>
>> rq can be NULL here? What's with the --count below then, wouldn't it
>> underflow since I assume rq == NULL means count == 0 as well?
> 
> Exactly. If rq is NULL then count must be 0. However, we want to show the
> output from before the BUG_ON so that we have it available in case the
> BUG does explode.

Okay makes sense.

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

Regards,

Tvrtko