Both of these were taking the mode_config mutex but executed from the
same work queue. If intel_crtc_page_flip happened to flush a work queue
containing an HPD event handler work item, deadlock resulted, since the
mutex required by the HPD handler was taken before the flush. Instead
use a separate work queue for the flip unpin work.
Signed-off-by: sabercrombie@xxxxxxxxxxxx
Reviewed-by: marcheu@xxxxxxxxxxxx
---
drivers/gpu/drm/i915/i915_dma.c | 21 ++++++++++++++++++++-
drivers/gpu/drm/i915/i915_drv.h | 1 +
drivers/gpu/drm/i915/intel_display.c | 4 ++--
3 files changed, 23 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 4f129bb..9215360 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -1558,6 +1558,22 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
goto out_mtrrfree;
}
+ /* intel_crtc_page_flip runs with the mode_config mutex having been
+ * taken in the DRM layer. It synchronously waits for pending unpin
+ * work items while holding this mutex. Therefore this queue cannot
+ * contain work items that take this mutex, such as HPD event
+ * handling, or we deadlock. There is also no reason for flipping to
+ * wait on such events. Therefore put flip unpinning in its own
+ * work queue.
+ */
+ dev_priv->flip_unpin_wq = alloc_ordered_workqueue("i915", 0);
+ if (dev_priv->flip_unpin_wq == NULL) {
+ DRM_ERROR("Failed to create flip unpin workqueue.\n");
+ destroy_workqueue(dev_priv->wq);
+ ret = -ENOMEM;
+ goto out_mtrrfree;
+ }
+
/* This must be called before any calls to HAS_PCH_* */
intel_detect_pch(dev);
@@ -1628,6 +1644,7 @@ out_gem_unload:
intel_teardown_gmbus(dev);
intel_teardown_mchbar(dev);
destroy_workqueue(dev_priv->wq);
+ destroy_workqueue(dev_priv->flip_unpin_wq);
out_mtrrfree:
if (dev_priv->mm.gtt_mtrr >= 0) {
mtrr_del(dev_priv->mm.gtt_mtrr,
@@ -1709,7 +1726,8 @@ int i915_driver_unload(struct drm_device *dev)
intel_opregion_fini(dev);
if (drm_core_check_feature(dev, DRIVER_MODESET)) {
- /* Flush any outstanding unpin_work. */
+ /* Flush any outstanding unpin, HPD, etc. work. */
+ flush_workqueue(dev_priv->flip_unpin_wq);
flush_workqueue(dev_priv->wq);
mutex_lock(&dev->struct_mutex);
@@ -1734,6 +1752,7 @@ int i915_driver_unload(struct drm_device *dev)
intel_teardown_mchbar(dev);
destroy_workqueue(dev_priv->wq);
+ destroy_workqueue(dev_priv->flip_unpin_wq);
pci_dev_put(dev_priv->bridge_dev);
kfree(dev->dev_private);
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 4130e6d..7eb4619 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -766,6 +766,7 @@ typedef struct drm_i915_private {
struct work_struct error_work;
struct completion error_completion;
struct workqueue_struct *wq;
+ struct workqueue_struct *flip_unpin_wq;
/* Display functions */
struct drm_i915_display_funcs display;
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index e204913..acd07dd 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -6937,7 +6937,7 @@ static void do_intel_finish_page_flip(struct drm_device *dev,
&obj->pending_flip.counter);
wake_up(&dev_priv->pending_flip_queue);
- queue_work(dev_priv->wq, &work->work);
+ queue_work(dev_priv->flip_unpin_wq, &work->work);
trace_i915_flip_complete(intel_crtc->plane, work->pending_flip_obj);
}
@@ -7305,7 +7305,7 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
spin_unlock_irqrestore(&dev->event_lock, flags);
if (atomic_read(&intel_crtc->unpin_work_count) >= 2)
- flush_workqueue(dev_priv->wq);
+ flush_workqueue(dev_priv->flip_unpin_wq);
ret = i915_mutex_lock_interruptible(dev);
if (ret)
--
1.8.4
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