From a16a405259b3648bda4c6732020b5fdf5ab01526 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Thu, 28 Apr 2016 09:56:56 +0100 Subject: [PATCH] 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: Chris Wilson Cc: Tvrtko Ursulin Reviewed-by: Joonas Lahtinen Link: http://patchwork.freedesktop.org/patch/msgid/1461833819-3991-22-git-send-email-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/i915_drv.h | 11 +++++++++++ drivers/gpu/drm/i915/i915_gem.c | 8 ++++---- drivers/gpu/drm/i915/intel_lrc.c | 14 ++++++++------ 3 files changed, 23 insertions(+), 10 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index 0bd9d17..eb4a95b 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -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; diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index e9bf45a..72cd084 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -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); } diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c index 3ab5caa..b7a3e7e 100644 --- a/drivers/gpu/drm/i915/intel_lrc.c +++ b/drivers/gpu/drm/i915/intel_lrc.c @@ -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); - engine->last_context = request->ctx; - } + /* 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); -- 2.7.4