From 1f7b847d72c3583df5048d83bd945d0c2c524c28 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Wed, 8 Feb 2017 14:30:33 +0000 Subject: [PATCH] drm/i915: Disable engine->irq_tasklet around resets When we restart the engines, and we have active requests, a request on the first engine may complete and queue a request to the second engine before we try to restart the second engine. That queueing of the request may race with the engine to restart, and so may corrupt the current state. Disabling the engine->irq_tasklet prevents the two paths from writing into ELSP simultaneously (and modifyin the execlists_port[] at the same time). Fixes: 821ed7df6e2a ("drm/i915: Update reset path to fix incomplete requests") Testcase: igt/gem_exec_fence/await-hang Signed-off-by: Chris Wilson Cc: Tvrtko Ursulin Cc: Mika Kuoppala Reviewed-by: Mika Kuoppala Link: http://patchwork.freedesktop.org/patch/msgid/20170208143033.11651-3-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/i915_gem.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index e8129935d78b..239e5144dbda 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -2643,6 +2643,15 @@ int i915_gem_reset_prepare(struct drm_i915_private *dev_priv) for_each_engine(engine, dev_priv, id) { struct drm_i915_gem_request *request; + /* Prevent request submission to the hardware until we have + * completed the reset in i915_gem_reset_finish(). If a request + * is completed by one engine, it may then queue a request + * to a second via its engine->irq_tasklet *just* as we are + * calling engine->init_hw() and also writing the ELSP. + * Turning off the engine->irq_tasklet until the reset is over + * prevents the race. + */ + tasklet_disable(&engine->irq_tasklet); tasklet_kill(&engine->irq_tasklet); if (engine_stalled(engine)) { @@ -2782,7 +2791,13 @@ void i915_gem_reset(struct drm_i915_private *dev_priv) void i915_gem_reset_finish(struct drm_i915_private *dev_priv) { + struct intel_engine_cs *engine; + enum intel_engine_id id; + lockdep_assert_held(&dev_priv->drm.struct_mutex); + + for_each_engine(engine, dev_priv, id) + tasklet_enable(&engine->irq_tasklet); } static void nop_submit_request(struct drm_i915_gem_request *request) -- 2.20.1