From 5dce5b9387a06eb9301fa1cede07922a5a4d7a29 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Mon, 20 Jan 2014 10:17:36 +0000 Subject: [PATCH] drm/i915: Wait for completion of pending flips when starved of fences On older generations (gen2, gen3) the GPU requires fences for many operations, such as blits. The display hardware also requires fences for scanouts and this leads to a situation where an arbitrary number of fences may be pinned by old scanouts following a pageflip but before we have executed the unpin workqueue. This is unpredictable by userspace and leads to random EDEADLK when submitting an otherwise benign execbuffer. However, we can detect when we have an outstanding flip and so cause userspace to wait upon their completion before finally declaring that the system is starved of fences. This is really no worse than forcing the GPU to stall waiting for older execbuffer to retire and release their fences before we can reallocate them for the next execbuffer. v2: move the test for a pending fb unpin to a common routine for later reuse during eviction Reported-and-tested-by: dimon@gmx.net Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=73696 Signed-off-by: Chris Wilson Reviewed-by: Jon Bloomfield Signed-off-by: Daniel Vetter --- drivers/gpu/drm/i915/i915_gem.c | 13 +++++++++---- drivers/gpu/drm/i915/intel_display.c | 24 ++++++++++++++++++++++++ drivers/gpu/drm/i915/intel_drv.h | 1 + 3 files changed, 34 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 4461336..00c8361 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -3106,7 +3106,7 @@ i915_find_fence_reg(struct drm_device *dev) } if (avail == NULL) - return NULL; + goto deadlock; /* None available, try to steal one or wait for a user to finish */ list_for_each_entry(reg, &dev_priv->mm.fence_list, lru_list) { @@ -3116,7 +3116,12 @@ i915_find_fence_reg(struct drm_device *dev) return reg; } - return NULL; +deadlock: + /* Wait for completion of pending flips which consume fences */ + if (intel_has_pending_fb_unpin(dev)) + return ERR_PTR(-EAGAIN); + + return ERR_PTR(-EDEADLK); } /** @@ -3161,8 +3166,8 @@ i915_gem_object_get_fence(struct drm_i915_gem_object *obj) } } else if (enable) { reg = i915_find_fence_reg(dev); - if (reg == NULL) - return -EDEADLK; + if (IS_ERR(reg)) + return PTR_ERR(reg); if (reg->obj) { struct drm_i915_gem_object *old = reg->obj; diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c index 14b024b..98371ee 100644 --- a/drivers/gpu/drm/i915/intel_display.c +++ b/drivers/gpu/drm/i915/intel_display.c @@ -2982,6 +2982,30 @@ static bool intel_crtc_has_pending_flip(struct drm_crtc *crtc) return pending; } +bool intel_has_pending_fb_unpin(struct drm_device *dev) +{ + struct intel_crtc *crtc; + + /* Note that we don't need to be called with mode_config.lock here + * as our list of CRTC objects is static for the lifetime of the + * device and so cannot disappear as we iterate. Similarly, we can + * happily treat the predicates as racy, atomic checks as userspace + * cannot claim and pin a new fb without at least acquring the + * struct_mutex and so serialising with us. + */ + list_for_each_entry(crtc, &dev->mode_config.crtc_list, base.head) { + if (atomic_read(&crtc->unpin_work_count) == 0) + continue; + + if (crtc->unpin_work) + intel_wait_for_vblank(dev, crtc->pipe); + + return true; + } + + return false; +} + static void intel_crtc_wait_for_pending_flips(struct drm_crtc *crtc) { struct drm_device *dev = crtc->dev; diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h index 8754db9..fbfaaba 100644 --- a/drivers/gpu/drm/i915/intel_drv.h +++ b/drivers/gpu/drm/i915/intel_drv.h @@ -626,6 +626,7 @@ void intel_ddi_get_config(struct intel_encoder *encoder, /* intel_display.c */ const char *intel_output_name(int output); +bool intel_has_pending_fb_unpin(struct drm_device *dev); int intel_pch_rawclk(struct drm_device *dev); void intel_mark_busy(struct drm_device *dev); void intel_mark_fb_busy(struct drm_i915_gem_object *obj, -- 2.7.4