drm/vmwgfx: Fix a circular locking dependency bug.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

3 files changed, 14 insertions, 19 deletions

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
index 3e4e670d321..356dc935ec1 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
@@ -113,6 +113,7 @@ struct vmw_fifo_state {
         unsigned long static_buffer_size;
         bool using_bounce_buffer;
         uint32_t capabilities;
+        struct mutex fifo_mutex;
         struct rw_semaphore rwsem;
 };
 
@@ -213,7 +214,7 @@ struct vmw_private {
          * Fencing and IRQs.
          */
 
-        uint32_t fence_seq;
+        atomic_t fence_seq;
         wait_queue_head_t fence_queue;
         wait_queue_head_t fifo_queue;
         atomic_t fence_queue_waiters;
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_fifo.c b/drivers/gpu/drm/vmwgfx/vmwgfx_fifo.c
index 4157547cc6e..39d43a01d84 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_fifo.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_fifo.c
@@ -74,6 +74,7 @@ int vmw_fifo_init(struct vmw_private *dev_priv, struct vmw_fifo_state *fifo)
         fifo->reserved_size = 0;
         fifo->using_bounce_buffer = false;
 
+        mutex_init(&fifo->fifo_mutex);
         init_rwsem(&fifo->rwsem);
 
         /*
@@ -117,7 +118,7 @@ int vmw_fifo_init(struct vmw_private *dev_priv, struct vmw_fifo_state *fifo)
                  (unsigned int) min,
                  (unsigned int) fifo->capabilities);
 
-        dev_priv->fence_seq = dev_priv->last_read_sequence;
+        atomic_set(&dev_priv->fence_seq, dev_priv->last_read_sequence);
         iowrite32(dev_priv->last_read_sequence, fifo_mem + SVGA_FIFO_FENCE);
 
         return vmw_fifo_send_fence(dev_priv, &dummy);
@@ -283,7 +284,7 @@ void *vmw_fifo_reserve(struct vmw_private *dev_priv, uint32_t bytes)
         uint32_t reserveable = fifo_state->capabilities & SVGA_FIFO_CAP_RESERVE;
         int ret;
 
-        down_write(&fifo_state->rwsem);
+        mutex_lock(&fifo_state->fifo_mutex);
         max = ioread32(fifo_mem + SVGA_FIFO_MAX);
         min = ioread32(fifo_mem + SVGA_FIFO_MIN);
         next_cmd = ioread32(fifo_mem + SVGA_FIFO_NEXT_CMD);
@@ -351,7 +352,7 @@ void *vmw_fifo_reserve(struct vmw_private *dev_priv, uint32_t bytes)
         }
 out_err:
         fifo_state->reserved_size = 0;
-        up_write(&fifo_state->rwsem);
+        mutex_unlock(&fifo_state->fifo_mutex);
         return NULL;
 }
 
@@ -426,6 +427,7 @@ void vmw_fifo_commit(struct vmw_private *dev_priv, uint32_t bytes)
 
         }
 
+        down_write(&fifo_state->rwsem);
         if (fifo_state->using_bounce_buffer || reserveable) {
                 next_cmd += bytes;
                 if (next_cmd >= max)
@@ -437,8 +439,9 @@ void vmw_fifo_commit(struct vmw_private *dev_priv, uint32_t bytes)
         if (reserveable)
                 iowrite32(0, fifo_mem + SVGA_FIFO_RESERVED);
         mb();
-        vmw_fifo_ping_host(dev_priv, SVGA_SYNC_GENERIC);
         up_write(&fifo_state->rwsem);
+        vmw_fifo_ping_host(dev_priv, SVGA_SYNC_GENERIC);
+        mutex_unlock(&fifo_state->fifo_mutex);
 }
 
 int vmw_fifo_send_fence(struct vmw_private *dev_priv, uint32_t *sequence)
@@ -451,9 +454,7 @@ int vmw_fifo_send_fence(struct vmw_private *dev_priv, uint32_t *sequence)
 
         fm = vmw_fifo_reserve(dev_priv, bytes);
         if (unlikely(fm == NULL)) {
-                down_write(&fifo_state->rwsem);
-                *sequence = dev_priv->fence_seq;
-                up_write(&fifo_state->rwsem);
+                *sequence = atomic_read(&dev_priv->fence_seq);
                 ret = -ENOMEM;
                 (void)vmw_fallback_wait(dev_priv, false, true, *sequence,
                                         false, 3*HZ);
@@ -461,7 +462,7 @@ int vmw_fifo_send_fence(struct vmw_private *dev_priv, uint32_t *sequence)
         }
 
         do {
-                *sequence = dev_priv->fence_seq++;
+                *sequence = atomic_add_return(1, &dev_priv->fence_seq);
         } while (*sequence == 0);
 
         if (!(fifo_state->capabilities & SVGA_FIFO_CAP_FENCE)) {
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_irq.c b/drivers/gpu/drm/vmwgfx/vmwgfx_irq.c
index d40086fc864..4d7cb539386 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_irq.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_irq.c
@@ -85,19 +85,12 @@ bool vmw_fence_signaled(struct vmw_private *dev_priv,
                 return true;
 
         /**
-         * Below is to signal stale fences that have wrapped.
-         * First, block fence submission.
-         */
-
-        down_read(&fifo_state->rwsem);
-
-        /**
          * Then check if the sequence is higher than what we've actually
          * emitted. Then the fence is stale and signaled.
          */
 
-        ret = ((dev_priv->fence_seq - sequence) > VMW_FENCE_WRAP);
-        up_read(&fifo_state->rwsem);
+        ret = ((atomic_read(&dev_priv->fence_seq) - sequence)
+               > VMW_FENCE_WRAP);
 
         return ret;
 }
@@ -127,7 +120,7 @@ int vmw_fallback_wait(struct vmw_private *dev_priv,
 
         if (fifo_idle)
                 down_read(&fifo_state->rwsem);
-        signal_seq = dev_priv->fence_seq;
+        signal_seq = atomic_read(&dev_priv->fence_seq);
         ret = 0;
 
         for (;;) {