1 files changed, 178 insertions, 0 deletions
diff --git a/linux-core/drm_bo_lock.c b/linux-core/drm_bo_lock.c
new file mode 100644
index 00000000..e5a86826
--- /dev/null
+++ b/linux-core/drm_bo_lock.c
@@ -0,0 +1,178 @@
+/**************************************************************************
+ *
+ * Copyright (c) 2007 Tungsten Graphics, Inc., Cedar Park, TX., USA
+ * All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sub license, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial portions
+ * of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+ * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+ * USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ **************************************************************************/
+/*
+ * Authors: Thomas Hellström <thomas-at-tungstengraphics-dot-com>
+ */
+
+/*
+ * This file implements a simple replacement for the buffer manager use
+ * of the heavyweight hardware lock.
+ * The lock is a read-write lock. Taking it in read mode is fast, and 
+ * intended for in-kernel use only.
+ * Taking it in write mode is slow.
+ *
+ * The write mode is used only when there is a need to block all 
+ * user-space processes from allocating a 
+ * new memory area.
+ * Typical use in write mode is X server VT switching, and it's allowed
+ * to leave kernel space with the write lock held. If a user-space process
+ * dies while having the write-lock, it will be released during the file
+ * descriptor release.
+ *
+ * The read lock is typically placed at the start of an IOCTL- or 
+ * user-space callable function that may end up allocating a memory area.
+ * This includes setstatus, super-ioctls and no_pfn; the latter may move
+ * unmappable regions to mappable. It's a bug to leave kernel space with the
+ * read lock held.
+ *
+ * Both read- and write lock taking is interruptible for low signal-delivery
+ * latency. The locking functions will return -EAGAIN if interrupted by a
+ * signal.
+ *
+ * Locking order: The lock should be taken BEFORE any kernel mutexes 
+ * or spinlocks.
+ */
+
+#include "drmP.h"
+
+void drm_bo_init_lock(struct drm_bo_lock *lock)
+{
+	DRM_INIT_WAITQUEUE(&lock->queue);
+	atomic_set(&lock->write_lock_pending, 0);
+	atomic_set(&lock->readers, 0);
+}
+
+void drm_bo_read_unlock(struct drm_bo_lock *lock)
+{
+	if (unlikely(atomic_add_negative(-1, &lock->readers)))
+		BUG();
+	if (atomic_read(&lock->readers) == 0)
+		wake_up_interruptible(&lock->queue);
+}
+
+EXPORT_SYMBOL(drm_bo_read_unlock);
+
+int drm_bo_read_lock(struct drm_bo_lock *lock)
+{
+	while (unlikely(atomic_read(&lock->write_lock_pending) != 0)) {
+		int ret;
+		ret = wait_event_interruptible
+		    (lock->queue, atomic_read(&lock->write_lock_pending) == 0);
+		if (ret)
+			return -EAGAIN;
+	}
+
+	while (unlikely(!atomic_add_unless(&lock->readers, 1, -1))) {
+		int ret;
+		ret = wait_event_interruptible
+		    (lock->queue, atomic_add_unless(&lock->readers, 1, -1));
+		if (ret)
+			return -EAGAIN;
+	}
+	return 0;
+}
+
+EXPORT_SYMBOL(drm_bo_read_lock);
+
+static int __drm_bo_write_unlock(struct drm_bo_lock *lock)
+{
+	if (unlikely(atomic_cmpxchg(&lock->readers, -1, 0) != -1))
+		return -EINVAL;
+	if (unlikely(atomic_cmpxchg(&lock->write_lock_pending, 1, 0) != 1))
+		return -EINVAL;
+	wake_up_interruptible(&lock->queue);
+	return 0;
+}
+
+static void drm_bo_write_lock_remove(struct drm_file *file_priv,
+				     struct drm_user_object *item)
+{
+	struct drm_bo_lock *lock = container_of(item, struct drm_bo_lock, base);
+	int ret;
+
+	ret = __drm_bo_write_unlock(lock);
+	BUG_ON(ret);
+}
+
+int drm_bo_write_lock(struct drm_bo_lock *lock, struct drm_file *file_priv)
+{
+	int ret = 0;
+	struct drm_device *dev;
+
+	if (unlikely(atomic_cmpxchg(&lock->write_lock_pending, 0, 1) != 0)) {
+		return -EINVAL;
+	}
+
+	while (unlikely(atomic_cmpxchg(&lock->readers, 0, -1) != 0)) {
+		ret = wait_event_interruptible
+		    (lock->queue, atomic_cmpxchg(&lock->readers, 0, -1) == 0);
+
+		if (ret) {
+			atomic_set(&lock->write_lock_pending, 0);
+			wake_up_interruptible(&lock->queue);
+			return -EAGAIN;
+		}
+	}
+
+	/*
+	 * Add a dummy user-object, the destructor of which will
+	 * make sure the lock is released if the client dies 
+	 * while holding it.
+	 */
+
+	dev = file_priv->head->dev;
+	mutex_lock(&dev->struct_mutex);
+	ret = drm_add_user_object(file_priv, &lock->base, 0);
+	lock->base.remove = &drm_bo_write_lock_remove;
+	lock->base.type = drm_lock_type;
+	if (ret) {
+		(void)__drm_bo_write_unlock(lock);
+	}
+	mutex_unlock(&dev->struct_mutex);
+
+	return ret;
+}
+
+int drm_bo_write_unlock(struct drm_bo_lock *lock, struct drm_file *file_priv)
+{
+	struct drm_device *dev = file_priv->head->dev;
+	struct drm_ref_object *ro;
+
+	mutex_lock(&dev->struct_mutex);
+
+	if (lock->base.owner != file_priv) {
+		mutex_unlock(&dev->struct_mutex);
+		return -EINVAL;
+	}
+	ro = drm_lookup_ref_object(file_priv, &lock->base, _DRM_REF_USE);
+	BUG_ON(!ro);
+	drm_remove_ref_object(file_priv, ro);
+	lock->base.owner = NULL;
+
+	mutex_unlock(&dev->struct_mutex);
+	return 0;
+}