From 48b5eaf303b60077faed09db77785d7a544ac335 Mon Sep 17 00:00:00 2001
From: Thomas Hellstrom <thomas-at-tungstengraphics-dot-com>
Date: Sat, 20 Oct 2007 16:49:43 +0200
Subject: Simple replacement for hardware lock in some cases. Fix i915 since
 last commit.

---
 linux-core/drm_bo_lock2.c | 99 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 99 insertions(+)
 create mode 100644 linux-core/drm_bo_lock2.c

(limited to 'linux-core/drm_bo_lock2.c')

diff --git a/linux-core/drm_bo_lock2.c b/linux-core/drm_bo_lock2.c
new file mode 100644
index 00000000..73e58bc0
--- /dev/null
+++ b/linux-core/drm_bo_lock2.c
@@ -0,0 +1,99 @@
+#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) == 0))
+		BUG();
+	if (atomic_read(&lock->readers) == 0)
+		wake_up_interruptible(&lock->queue);
+}
+
+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;
+}
+		
+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;
+		}
+	}
+	
+	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)
+{
+	return drm_user_object_unref(file_priv, lock->base.hash.key, 
+				     drm_lock_type);
+}
-- 
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