[Intel-gfx] [PATCH] drm/i915/execlists: Fixup cancel_port_requests()

[Tvrtko Ursulin]

On 25/11/2019 11:25, Chris Wilson wrote:
> I rushed a last minute correction to cancel_port_requests() to prevent
> the snooping of *execlists->active as the inflight array was being
> updated, without noticing we iterated the inflight array starting from
> active! Oops.
> 
> Fixes: 331bf9059157 ("drm/i915/gt: Mark the execlists->active as the primary volatile access")
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> ---
>   drivers/gpu/drm/i915/gt/intel_lrc.c | 16 +++++++---------
>   1 file changed, 7 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
> index e533ff7ba334..6090357a00fa 100644
> --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> @@ -2007,19 +2007,17 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
>   static void
>   cancel_port_requests(struct intel_engine_execlists * const execlists)
>   {
> -	struct i915_request * const *port, *rq;
> +	struct i915_request * const *port;
>   
> -	for (port = execlists->pending; (rq = *port); port++)
> -		execlists_schedule_out(rq);
> +	for (port = execlists->pending; *port; port++)
> +		execlists_schedule_out(*port);
>   	memset(execlists->pending, 0, sizeof(execlists->pending));
>   
>   	/* Mark the end of active before we overwrite *active */
> -	WRITE_ONCE(execlists->active, execlists->pending);
> -
> -	for (port = execlists->active; (rq = *port); port++)
> -		execlists_schedule_out(rq);
> -	execlists->active =
> -		memset(execlists->inflight, 0, sizeof(execlists->inflight));
> +	for (port = xchg(&execlists->active, execlists->pending); *port; port++)
> +		execlists_schedule_out(*port);
> +	WRITE_ONCE(execlists->active,
> +		   memset(execlists->inflight, 0, sizeof(execlists->inflight)));
>   }
>   
>   static inline void
> 

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

Regards,

Tvrtko