Bugzilla Bug #9457

Add refcounting of user waiters to the DRM hardware lock, so that we can use the
DRM_LOCK_CONT flag more conservatively.

Also add a kernel waiter refcount that if nonzero transfers the lock for the kernel context,
when it is released. This is useful when waiting for idle and can be used
for very simple fence object driver implementations for the new memory manager.

It also resolves the AIGLX startup deadlock for the sis and the via drivers.
i810, i830 still require that the hardware lock is really taken so the deadlock remains
for those two. I'm not sure about ffb. Anyone familiar with that code?

1 files changed, 35 insertions, 22 deletions

diff --git a/linux-core/drm_fops.c b/linux-core/drm_fops.c
index 84e06c87..faf76726 100644
--- a/linux-core/drm_fops.c
+++ b/linux-core/drm_fops.c
@@ -427,38 +427,51 @@ int drm_release(struct inode *inode, struct file *filp)
 		  dev->open_count);
 
 	if (dev->driver->reclaim_buffers_locked && dev->lock.hw_lock) {
-	        unsigned long _end = jiffies + DRM_HZ*3;
-
-		do {
-			retcode = drm_kernel_take_hw_lock(filp);
-		} while(retcode && !time_after_eq(jiffies,_end));
-
-		if (!retcode) {
+		if (drm_i_have_hw_lock(filp)) {
 			dev->driver->reclaim_buffers_locked(dev, filp);
-
-			drm_lock_free(dev, &dev->lock.hw_lock->lock,
-				      _DRM_LOCKING_CONTEXT(dev->lock.hw_lock->lock));
 		} else {
+			unsigned long _end=jiffies + 3*DRM_HZ;
+			int locked = 0;
+
+			drm_idlelock_take(&dev->lock);
 
 			/*
-			 * FIXME: This is not a good solution. We should perhaps associate the
-			 * DRM lock with a process context, and check whether the current process
-			 * holds the lock. Then we can run reclaim buffers locked anyway.
+			 * Wait for a while.
 			 */
 
-			DRM_ERROR("Reclaim buffers locked deadlock.\n"
-				  "\tThis is probably a single thread having multiple\n"
-				  "\tDRM file descriptors open either dying or"
-				  " closing file descriptors\n"
-				  "\twhile having the lock. I will not reclaim buffers.\n"
-				  "\tLocking context is 0x%08x\n",
-				  _DRM_LOCKING_CONTEXT(dev->lock.hw_lock->lock));
+			do{
+				spin_lock(&dev->lock.spinlock);
+				locked = dev->lock.idle_has_lock;
+				spin_unlock(&dev->lock.spinlock);
+				if (locked)
+					break;
+				schedule();
+			} while (!time_after_eq(jiffies, _end));
+
+			if (!locked) {
+				DRM_ERROR("reclaim_buffers_locked() deadlock. Please rework this\n"
+					  "\tdriver to use reclaim_buffers_idlelocked() instead.\n"
+					  "\tI will go on reclaiming the buffers anyway.\n");
+			}
+
+			dev->driver->reclaim_buffers_locked(dev, filp);
+			drm_idlelock_release(&dev->lock);
 		}
-	} else if (drm_i_have_hw_lock(filp)) {
+	}
+
+	if (dev->driver->reclaim_buffers_idlelocked && dev->lock.hw_lock) {
+
+		drm_idlelock_take(&dev->lock);
+		dev->driver->reclaim_buffers_idlelocked(dev, filp);
+		drm_idlelock_release(&dev->lock);
+
+	}
+
+	if (drm_i_have_hw_lock(filp)) {
 		DRM_DEBUG("File %p released, freeing lock for context %d\n",
 			  filp, _DRM_LOCKING_CONTEXT(dev->lock.hw_lock->lock));
 
-		drm_lock_free(dev, &dev->lock.hw_lock->lock,
+		drm_lock_free(&dev->lock,
 			      _DRM_LOCKING_CONTEXT(dev->lock.hw_lock->lock));
 	}