Reapply "drm/qxl: simplify qxl_fence_wait"

This reverts commit 07ed11a.

Stephen Rostedt reports:
 "I went to run my tests on my VMs and the tests hung on boot up.
  Unfortunately, the most I ever got out was:

  [   93.607888] Testing event system initcall: OK
  [   93.667730] Running tests on all trace events:
  [   93.669757] Testing all events: OK
  [   95.631064] ------------[ cut here ]------------
  Timed out after 60 seconds"

and further debugging points to a possible circular locking dependency
between the console_owner locking and the worker pool locking.

Reverting the commit allows Steve's VM to boot to completion again.

[ This may obviously result in the "[TTM] Buffer eviction failed"
  messages again, which was the reason for that original revert. But at
  this point this seems preferable to a non-booting system... ]

Reported-and-bisected-by: Steven Rostedt <[email protected]>
Link: https://lore.kernel.org/all/[email protected]/
Acked-by: Maxime Ripard <[email protected]>
Cc: Alex Constantino <[email protected]>
Cc: Maxime Ripard <[email protected]>
Cc: Timo Lindfors <[email protected]>
Cc: Dave Airlie <[email protected]>
Cc: Gerd Hoffmann <[email protected]>
Cc: Maarten Lankhorst <[email protected]>
Cc: Thomas Zimmermann <[email protected]>
Cc: Daniel Vetter <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: torvalds

drivers/gpu/drm/qxl/qxl_release.c

@@ -58,56 +58,16 @@ static long qxl_fence_wait(struct dma_fence *fence, bool intr,
 			   signed long timeout)
 {
 	struct qxl_device *qdev;
-	struct qxl_release *release;
-	int count = 0, sc = 0;
-	bool have_drawable_releases;
 	unsigned long cur, end = jiffies + timeout;
 
 	qdev = container_of(fence->lock, struct qxl_device, release_lock);
-	release = container_of(fence, struct qxl_release, base);
-	have_drawable_releases = release->type == QXL_RELEASE_DRAWABLE;
-
-retry:
-	sc++;
-
-	if (dma_fence_is_signaled(fence))
-		goto signaled;
-
-	qxl_io_notify_oom(qdev);
-
-	for (count = 0; count < 11; count++) {
-		if (!qxl_queue_garbage_collect(qdev, true))
-			break;
-
-		if (dma_fence_is_signaled(fence))
-			goto signaled;
-	}
-
-	if (dma_fence_is_signaled(fence))
-		goto signaled;
 
-	if (have_drawable_releases || sc < 4) {
-		if (sc > 2)
-			/* back off */
-			usleep_range(500, 1000);
-
-		if (time_after(jiffies, end))
-			return 0;
-
-		if (have_drawable_releases && sc > 300) {
-			DMA_FENCE_WARN(fence,
-				       "failed to wait on release %llu after spincount %d\n",
-				       fence->context & ~0xf0000000, sc);
-			goto signaled;
-		}
-		goto retry;
-	}
-	/*
-	 * yeah, original sync_obj_wait gave up after 3 spins when
-	 * have_drawable_releases is not set.
-	 */
+	if (!wait_event_timeout(qdev->release_event,
+				(dma_fence_is_signaled(fence) ||
+				 (qxl_io_notify_oom(qdev), 0)),
+				timeout))
+		return 0;
 
-signaled:
 	cur = jiffies;
 	if (time_after(cur, end))
 		return 0;

include/linux/dma-fence.h

@@ -682,11 +682,4 @@ static inline bool dma_fence_is_container(struct dma_fence *fence)
 	return dma_fence_is_array(fence) || dma_fence_is_chain(fence);
 }
 
-#define DMA_FENCE_WARN(f, fmt, args...) \
-	do {								\
-		struct dma_fence *__ff = (f);				\
-		pr_warn("f %llu#%llu: " fmt, __ff->context, __ff->seqno,\
-			 ##args);					\
-	} while (0)
-
 #endif /* __LINUX_DMA_FENCE_H */