1 files changed, 106 insertions, 28 deletions

diff --git a/drivers/char/drm/drm_lock.c b/drivers/char/drm/drm_lock.c
index e9993ba461a2..befd1af19dfe 100644
--- a/drivers/char/drm/drm_lock.c
+++ b/drivers/char/drm/drm_lock.c
@@ -35,9 +35,6 @@
 
 #include "drmP.h"
 
-static int drm_lock_transfer(drm_device_t * dev,
-                             __volatile__ unsigned int *lock,
-                             unsigned int context);
 static int drm_notifier(void *priv);
 
 /**
@@ -80,6 +77,9 @@ int drm_lock(struct inode *inode, struct file *filp,
                         return -EINVAL;
 
         add_wait_queue(&dev->lock.lock_queue, &entry);
+        spin_lock(&dev->lock.spinlock);
+        dev->lock.user_waiters++;
+        spin_unlock(&dev->lock.spinlock);
         for (;;) {
                 __set_current_state(TASK_INTERRUPTIBLE);
                 if (!dev->lock.hw_lock) {
@@ -87,7 +87,7 @@ int drm_lock(struct inode *inode, struct file *filp,
                         ret = -EINTR;
                         break;
                 }
-                if (drm_lock_take(&dev->lock.hw_lock->lock, lock.context)) {
+                if (drm_lock_take(&dev->lock, lock.context)) {
                         dev->lock.filp = filp;
                         dev->lock.lock_time = jiffies;
                         atomic_inc(&dev->counts[_DRM_STAT_LOCKS]);
@@ -101,12 +101,14 @@ int drm_lock(struct inode *inode, struct file *filp,
                         break;
                 }
         }
+        spin_lock(&dev->lock.spinlock);
+        dev->lock.user_waiters--;
+        spin_unlock(&dev->lock.spinlock);
         __set_current_state(TASK_RUNNING);
         remove_wait_queue(&dev->lock.lock_queue, &entry);
 
-        DRM_DEBUG("%d %s\n", lock.context, ret ? "interrupted" : "has lock");
-        if (ret)
-                return ret;
+        DRM_DEBUG( "%d %s\n", lock.context, ret ? "interrupted" : "has lock" );
+        if (ret) return ret;
 
         sigemptyset(&dev->sigmask);
         sigaddset(&dev->sigmask, SIGSTOP);
@@ -127,14 +129,12 @@ int drm_lock(struct inode *inode, struct file *filp,
                 }
         }
 
-        /* dev->driver->kernel_context_switch isn't used by any of the x86
-         *  drivers but is used by the Sparc driver.
-         */
         if (dev->driver->kernel_context_switch &&
             dev->last_context != lock.context) {
                 dev->driver->kernel_context_switch(dev, dev->last_context,
                                                    lock.context);
         }
+
         return 0;
 }
 
@@ -184,12 +184,8 @@ int drm_unlock(struct inode *inode, struct file *filp,
         if (dev->driver->kernel_context_switch_unlock)
                 dev->driver->kernel_context_switch_unlock(dev);
         else {
-                drm_lock_transfer(dev, &dev->lock.hw_lock->lock,
-                                  DRM_KERNEL_CONTEXT);
-
-                if (drm_lock_free(dev, &dev->lock.hw_lock->lock,
-                                  DRM_KERNEL_CONTEXT)) {
-                        DRM_ERROR("\n");
+                if (drm_lock_free(&dev->lock,lock.context)) {
+                        /* FIXME: Should really bail out here. */
                 }
         }
 
@@ -206,18 +202,26 @@ int drm_unlock(struct inode *inode, struct file *filp,
  *
  * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
  */
-int drm_lock_take(__volatile__ unsigned int *lock, unsigned int context)
+int drm_lock_take(drm_lock_data_t *lock_data,
+                  unsigned int context)
 {
         unsigned int old, new, prev;
+        volatile unsigned int *lock = &lock_data->hw_lock->lock;
 
+        spin_lock(&lock_data->spinlock);
         do {
                 old = *lock;
                 if (old & _DRM_LOCK_HELD)
                         new = old | _DRM_LOCK_CONT;
-                else
-                        new = context | _DRM_LOCK_HELD;
+                else {
+                        new = context | _DRM_LOCK_HELD |
+                                ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
+                                 _DRM_LOCK_CONT : 0);
+                }
                 prev = cmpxchg(lock, old, new);
         } while (prev != old);
+        spin_unlock(&lock_data->spinlock);
+
         if (_DRM_LOCKING_CONTEXT(old) == context) {
                 if (old & _DRM_LOCK_HELD) {
                         if (context != DRM_KERNEL_CONTEXT) {
@@ -227,7 +231,8 @@ int drm_lock_take(__volatile__ unsigned int *lock, unsigned int context)
                         return 0;
                 }
         }
-        if (new == (context | _DRM_LOCK_HELD)) {
+
+        if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) {
                 /* Have lock */
                 return 1;
         }
@@ -246,13 +251,13 @@ int drm_lock_take(__volatile__ unsigned int *lock, unsigned int context)
  * Resets the lock file pointer.
  * Marks the lock as held by the given context, via the \p cmpxchg instruction.
  */
-static int drm_lock_transfer(drm_device_t * dev,
-                             __volatile__ unsigned int *lock,
+static int drm_lock_transfer(drm_lock_data_t *lock_data,
                              unsigned int context)
 {
         unsigned int old, new, prev;
+        volatile unsigned int *lock = &lock_data->hw_lock->lock;
 
-        dev->lock.filp = NULL;
+        lock_data->filp = NULL;
         do {
                 old = *lock;
                 new = context | _DRM_LOCK_HELD;
@@ -272,23 +277,32 @@ static int drm_lock_transfer(drm_device_t * dev,
  * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
  * waiting on the lock queue.
  */
-int drm_lock_free(drm_device_t * dev,
-                  __volatile__ unsigned int *lock, unsigned int context)
+int drm_lock_free(drm_lock_data_t *lock_data, unsigned int context)
 {
         unsigned int old, new, prev;
+        volatile unsigned int *lock = &lock_data->hw_lock->lock;
+
+        spin_lock(&lock_data->spinlock);
+        if (lock_data->kernel_waiters != 0) {
+                drm_lock_transfer(lock_data, 0);
+                lock_data->idle_has_lock = 1;
+                spin_unlock(&lock_data->spinlock);
+                return 1;
+        }
+        spin_unlock(&lock_data->spinlock);
 
-        dev->lock.filp = NULL;
         do {
                 old = *lock;
-                new = 0;
+                new = _DRM_LOCKING_CONTEXT(old);
                 prev = cmpxchg(lock, old, new);
         } while (prev != old);
+
         if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
                 DRM_ERROR("%d freed heavyweight lock held by %d\n",
                           context, _DRM_LOCKING_CONTEXT(old));
                 return 1;
         }
-        wake_up_interruptible(&dev->lock.lock_queue);
+        wake_up_interruptible(&lock_data->lock_queue);
         return 0;
 }
 
@@ -322,3 +336,67 @@ static int drm_notifier(void *priv)
         } while (prev != old);
         return 0;
 }
+
+/**
+ * This function returns immediately and takes the hw lock
+ * with the kernel context if it is free, otherwise it gets the highest priority when and if
+ * it is eventually released.
+ *
+ * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held
+ * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause
+ * a deadlock, which is why the "idlelock" was invented).
+ *
+ * This should be sufficient to wait for GPU idle without
+ * having to worry about starvation.
+ */
+
+void drm_idlelock_take(drm_lock_data_t *lock_data)
+{
+        int ret = 0;
+
+        spin_lock(&lock_data->spinlock);
+        lock_data->kernel_waiters++;
+        if (!lock_data->idle_has_lock) {
+
+                spin_unlock(&lock_data->spinlock);
+                ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
+                spin_lock(&lock_data->spinlock);
+
+                if (ret == 1)
+                        lock_data->idle_has_lock = 1;
+        }
+        spin_unlock(&lock_data->spinlock);
+}
+EXPORT_SYMBOL(drm_idlelock_take);
+
+void drm_idlelock_release(drm_lock_data_t *lock_data)
+{
+        unsigned int old, prev;
+        volatile unsigned int *lock = &lock_data->hw_lock->lock;
+
+        spin_lock(&lock_data->spinlock);
+        if (--lock_data->kernel_waiters == 0) {
+                if (lock_data->idle_has_lock) {
+                        do {
+                                old = *lock;
+                                prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT);
+                        } while (prev != old);
+                        wake_up_interruptible(&lock_data->lock_queue);
+                        lock_data->idle_has_lock = 0;
+                }
+        }
+        spin_unlock(&lock_data->spinlock);
+}
+EXPORT_SYMBOL(drm_idlelock_release);
+
+
+int drm_i_have_hw_lock(struct file *filp)
+{
+        DRM_DEVICE;
+
+        return (priv->lock_count && dev->lock.hw_lock &&
+                _DRM_LOCK_IS_HELD(dev->lock.hw_lock->lock) &&
+                dev->lock.filp == filp);
+}
+
+EXPORT_SYMBOL(drm_i_have_hw_lock);