Re: [PATCH] drm/i915/execlists: Set priority hint prior to submission

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Chris Wilson <chris@chris-wilson.co.uk> writes:

> Quoting Chris Wilson (2019-08-21 15:23:36)
>> Since we now run process_csb() outside of the engine->active.lock, we
>> can process a CS-event immediately upon our ELSP write. As we currently
>> inspect the pending queue *after* the ELSP write, there is an
>> opportunity for a CS-event to update the pending queue before we can
>> read it, making ourselves chases an invalid pointer.
>> 
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111427

Enough to make me convinced,
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>

>> Fixes: df403069029d ("drm/i915/execlists: Lift process_csb() out of the irq-off spinlock")
>> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
>> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
>> ---
>>  drivers/gpu/drm/i915/gt/intel_lrc.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
>> index 44780e7fafec..d42584439f51 100644
>> --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
>> +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
>> @@ -1335,9 +1335,9 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
>>         if (submit) {
>>                 *port = execlists_schedule_in(last, port - execlists->pending);
>>                 memset(port + 1, 0, (last_port - port) * sizeof(*port));
>> -               execlists_submit_ports(engine);
>>                 execlists->switch_priority_hint =
>>                         switch_prio(engine, *execlists->pending);
>> +               execlists_submit_ports(engine);
>>         } else {
>>                 ring_set_paused(engine, 0);
>>         }
>> -- 
>> 2.23.0.rc1
>> 
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