Re: [Intel-gfx] [PATCH 04/57] drm/i915: Protect against request freeing during cancellation on wedging

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

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

> As soon as we mark a request as completed, it may be retired. So when
> cancelling a request and marking it complete, make sure we first keep a
> reference to the request.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>

> ---
>  .../drm/i915/gt/intel_execlists_submission.c  | 19 +++++++++++--------
>  drivers/gpu/drm/i915/gt/intel_reset.c         | 15 ++++++---------
>  .../gpu/drm/i915/gt/intel_ring_submission.c   |  2 +-
>  drivers/gpu/drm/i915/gt/mock_engine.c         |  8 +++++---
>  drivers/gpu/drm/i915/i915_request.c           |  9 +++++++--
>  drivers/gpu/drm/i915/i915_request.h           |  2 +-
>  6 files changed, 31 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> index e7593df6777d..45a8ac152b88 100644
> --- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> +++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> @@ -2976,7 +2976,7 @@ static void execlists_reset_cancel(struct intel_engine_cs *engine)
>  
>  	/* Mark all executing requests as skipped. */
>  	list_for_each_entry(rq, &engine->active.requests, sched.link)
> -		i915_request_mark_eio(rq);
> +		i915_request_put(i915_request_mark_eio(rq));
>  	intel_engine_signal_breadcrumbs(engine);
>  
>  	/* Flush the queued requests to the timeline list (for retiring). */
> @@ -2984,8 +2984,10 @@ static void execlists_reset_cancel(struct intel_engine_cs *engine)
>  		struct i915_priolist *p = to_priolist(rb);
>  
>  		priolist_for_each_request_consume(rq, rn, p) {
> -			i915_request_mark_eio(rq);
> -			__i915_request_submit(rq);
> +			if (i915_request_mark_eio(rq)) {
> +				__i915_request_submit(rq);
> +				i915_request_put(rq);
> +			}
>  		}
>  
>  		rb_erase_cached(&p->node, &execlists->queue);
> @@ -2994,7 +2996,7 @@ static void execlists_reset_cancel(struct intel_engine_cs *engine)
>  
>  	/* On-hold requests will be flushed to timeline upon their release */
>  	list_for_each_entry(rq, &engine->active.hold, sched.link)
> -		i915_request_mark_eio(rq);
> +		i915_request_put(i915_request_mark_eio(rq));
>  
>  	/* Cancel all attached virtual engines */
>  	while ((rb = rb_first_cached(&execlists->virtual))) {
> @@ -3007,10 +3009,11 @@ static void execlists_reset_cancel(struct intel_engine_cs *engine)
>  		spin_lock(&ve->base.active.lock);
>  		rq = fetch_and_zero(&ve->request);
>  		if (rq) {
> -			i915_request_mark_eio(rq);
> -
> -			rq->engine = engine;
> -			__i915_request_submit(rq);
> +			if (i915_request_mark_eio(rq)) {
> +				rq->engine = engine;
> +				__i915_request_submit(rq);
> +				i915_request_put(rq);
> +			}
>  			i915_request_put(rq);
>  
>  			ve->base.execlists.queue_priority_hint = INT_MIN;
> diff --git a/drivers/gpu/drm/i915/gt/intel_reset.c b/drivers/gpu/drm/i915/gt/intel_reset.c
> index 107430e1e864..a82c4d7b23bc 100644
> --- a/drivers/gpu/drm/i915/gt/intel_reset.c
> +++ b/drivers/gpu/drm/i915/gt/intel_reset.c
> @@ -786,18 +786,15 @@ static void reset_finish(struct intel_gt *gt, intel_engine_mask_t awake)
>  
>  static void nop_submit_request(struct i915_request *request)
>  {
> -	struct intel_engine_cs *engine = request->engine;
> -	unsigned long flags;
> -
>  	RQ_TRACE(request, "-EIO\n");
> -	i915_request_set_error_once(request, -EIO);
>  
> -	spin_lock_irqsave(&engine->active.lock, flags);
> -	__i915_request_submit(request);
> -	i915_request_mark_complete(request);
> -	spin_unlock_irqrestore(&engine->active.lock, flags);
> +	request = i915_request_mark_eio(request);
> +	if (request) {
> +		i915_request_submit(request);
> +		intel_engine_signal_breadcrumbs(request->engine);
>  
> -	intel_engine_signal_breadcrumbs(engine);
> +		i915_request_put(request);
> +	}
>  }
>  
>  static void __intel_gt_set_wedged(struct intel_gt *gt)
> diff --git a/drivers/gpu/drm/i915/gt/intel_ring_submission.c b/drivers/gpu/drm/i915/gt/intel_ring_submission.c
> index 8b7cc637c432..9c2c605d7a92 100644
> --- a/drivers/gpu/drm/i915/gt/intel_ring_submission.c
> +++ b/drivers/gpu/drm/i915/gt/intel_ring_submission.c
> @@ -400,7 +400,7 @@ static void reset_cancel(struct intel_engine_cs *engine)
>  
>  	/* Mark all submitted requests as skipped. */
>  	list_for_each_entry(request, &engine->active.requests, sched.link)
> -		i915_request_mark_eio(request);
> +		i915_request_put(i915_request_mark_eio(request));
>  	intel_engine_signal_breadcrumbs(engine);
>  
>  	/* Remaining _unready_ requests will be nop'ed when submitted */
> diff --git a/drivers/gpu/drm/i915/gt/mock_engine.c b/drivers/gpu/drm/i915/gt/mock_engine.c
> index df7c1b1acc32..cf1269e74998 100644
> --- a/drivers/gpu/drm/i915/gt/mock_engine.c
> +++ b/drivers/gpu/drm/i915/gt/mock_engine.c
> @@ -239,13 +239,15 @@ static void mock_reset_cancel(struct intel_engine_cs *engine)
>  
>  	/* Mark all submitted requests as skipped. */
>  	list_for_each_entry(rq, &engine->active.requests, sched.link)
> -		i915_request_mark_eio(rq);
> +		i915_request_put(i915_request_mark_eio(rq));
>  	intel_engine_signal_breadcrumbs(engine);
>  
>  	/* Cancel and submit all pending requests. */
>  	list_for_each_entry(rq, &mock->hw_queue, mock.link) {
> -		i915_request_mark_eio(rq);
> -		__i915_request_submit(rq);
> +		if (i915_request_mark_eio(rq)) {
> +			__i915_request_submit(rq);
> +			i915_request_put(rq);
> +		}
>  	}
>  	INIT_LIST_HEAD(&mock->hw_queue);
>  
> diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
> index d66981b083cd..a336d6c40d8b 100644
> --- a/drivers/gpu/drm/i915/i915_request.c
> +++ b/drivers/gpu/drm/i915/i915_request.c
> @@ -514,15 +514,20 @@ void i915_request_set_error_once(struct i915_request *rq, int error)
>  	} while (!try_cmpxchg(&rq->fence.error, &old, error));
>  }
>  
> -void i915_request_mark_eio(struct i915_request *rq)
> +struct i915_request *i915_request_mark_eio(struct i915_request *rq)
>  {
>  	if (__i915_request_is_complete(rq))
> -		return;
> +		return NULL;
>  
>  	GEM_BUG_ON(i915_request_signaled(rq));
>  
> +	/* As soon as the request is completed, it may be retired */
> +	rq = i915_request_get(rq);
> +
>  	i915_request_set_error_once(rq, -EIO);
>  	i915_request_mark_complete(rq);
> +
> +	return rq;
>  }
>  
>  bool __i915_request_submit(struct i915_request *request)
> diff --git a/drivers/gpu/drm/i915/i915_request.h b/drivers/gpu/drm/i915/i915_request.h
> index 1bfe214a47e9..c0bd4cb8786a 100644
> --- a/drivers/gpu/drm/i915/i915_request.h
> +++ b/drivers/gpu/drm/i915/i915_request.h
> @@ -311,7 +311,7 @@ i915_request_create(struct intel_context *ce);
>  
>  void __i915_request_skip(struct i915_request *rq);
>  void i915_request_set_error_once(struct i915_request *rq, int error);
> -void i915_request_mark_eio(struct i915_request *rq);
> +struct i915_request *i915_request_mark_eio(struct i915_request *rq);
>  
>  struct i915_request *__i915_request_commit(struct i915_request *request);
>  void __i915_request_queue(struct i915_request *rq,
> -- 
> 2.20.1
>
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