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Commit a16a4052 authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915: Track the previous pinned context inside the request 



As the contexts are accessed by the hardware until the switch is completed
to a new context, the hardware may still be writing to the context object
after the breadcrumb is visible. We must not unpin/unbind/prune that
object whilst still active and so we keep the previous context pinned until
the following request. We can generalise the tracking we already do via
the engine->last_context and move it to the request so that it works
equally for execlists and GuC.

v2: Drop the execlists double pin as that exposes a race inside the lrc
irq handler as it tries to access the context after it may be retired.

Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Reviewed-by: default avatarJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461833819-3991-22-git-send-email-chris@chris-wilson.co.uk
parent 73db04cf

drivers/gpu/drm/i915/i915_drv.h

+11 −0
Original line number Diff line number Diff line
@@ -2305,6 +2305,17 @@ struct drm_i915_gem_request { 
	struct intel_context *ctx;

	struct intel_ringbuffer *ringbuf;



	/**

	 * Context related to the previous request.

	 * As the contexts are accessed by the hardware until the switch is

	 * completed to a new context, the hardware may still be writing

	 * to the context object after the breadcrumb is visible. We must

	 * not unpin/unbind/prune that object whilst still active and so

	 * we keep the previous context pinned until the following (this)

	 * request is retired.

	 */

	struct intel_context *previous_context;



	/** Batch buffer related to this request if any (used for

	    error state dump only) */

	struct drm_i915_gem_object *batch_obj;

drivers/gpu/drm/i915/i915_gem.c

+4 −4
Original line number Diff line number Diff line
@@ -1413,13 +1413,13 @@ static void i915_gem_request_retire(struct drm_i915_gem_request *request) 
	list_del_init(&request->list);

	i915_gem_request_remove_from_client(request);



	if (request->ctx) {

	if (request->previous_context) {

		if (i915.enable_execlists)

			intel_lr_context_unpin(request->ctx, request->engine);



		i915_gem_context_unreference(request->ctx);

			intel_lr_context_unpin(request->previous_context,

					       request->engine);

	}



	i915_gem_context_unreference(request->ctx);

	i915_gem_request_unreference(request);

}

drivers/gpu/drm/i915/intel_lrc.c

+8 −6
Original line number Diff line number Diff line
@@ -771,12 +771,14 @@ intel_logical_ring_advance_and_submit(struct drm_i915_gem_request *request) 
	if (intel_engine_stopped(engine))

		return 0;



	if (engine->last_context != request->ctx) {

		if (engine->last_context)

			intel_lr_context_unpin(engine->last_context, engine);

		intel_lr_context_pin(request->ctx, engine);

	/* We keep the previous context alive until we retire the following

	 * request. This ensures that any the context object is still pinned

	 * for any residual writes the HW makes into it on the context switch

	 * into the next object following the breadcrumb. Otherwise, we may

	 * retire the context too early.

	 */

	request->previous_context = engine->last_context;

	engine->last_context = request->ctx;

	}



	if (dev_priv->guc.execbuf_client)

		i915_guc_submit(dev_priv->guc.execbuf_client, request);