drm/vmwgfx: Reorganize the fence wait loop

Reorganize the fence wait loop somewhat to make it look more like the
examples in set_current_state() kerneldoc, and add some code comments.

Also if we're about to time out, make sure we check again whether the fence
is actually signaled.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Deepak Rawat <drawat@vmware.com>

1 files changed, 26 insertions, 12 deletions

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c b/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c
index 9ed544f8958f..ea41d74d8341 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c
@@ -175,7 +175,6 @@ static long vmw_fence_wait(struct dma_fence *f, bool intr, signed long timeout)
         struct vmw_private *dev_priv = fman->dev_priv;
         struct vmwgfx_wait_cb cb;
         long ret = timeout;
-        unsigned long irq_flags;
 
         if (likely(vmw_fence_obj_signaled(fence)))
                 return timeout;
@@ -183,7 +182,7 @@ static long vmw_fence_wait(struct dma_fence *f, bool intr, signed long timeout)
         vmw_fifo_ping_host(dev_priv, SVGA_SYNC_GENERIC);
         vmw_seqno_waiter_add(dev_priv);
 
-        spin_lock_irqsave(f->lock, irq_flags);
+        spin_lock(f->lock);
 
         if (intr && signal_pending(current)) {
                 ret = -ERESTARTSYS;
@@ -194,30 +193,45 @@ static long vmw_fence_wait(struct dma_fence *f, bool intr, signed long timeout)
         cb.task = current;
         list_add(&cb.base.node, &f->cb_list);
 
-        while (ret > 0) {
+        for (;;) {
                 __vmw_fences_update(fman);
-                if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &f->flags))
-                        break;
 
+                /*
+                 * We can use the barrier free __set_current_state() since
+                 * DMA_FENCE_FLAG_SIGNALED_BIT + wakeup is protected by the
+                 * fence spinlock.
+                 */
                 if (intr)
                         __set_current_state(TASK_INTERRUPTIBLE);
                 else
                         __set_current_state(TASK_UNINTERRUPTIBLE);
-                spin_unlock_irqrestore(f->lock, irq_flags);
 
-                ret = schedule_timeout(ret);
+                if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &f->flags)) {
+                        if (ret == 0 && timeout > 0)
+                                ret = 1;
+                        break;
+                }
 
-                spin_lock_irqsave(f->lock, irq_flags);
-                if (ret > 0 && intr && signal_pending(current))
+                if (intr && signal_pending(current)) {
                         ret = -ERESTARTSYS;
-        }
+                        break;
+                }
 
+                if (ret == 0)
+                        break;
+
+                spin_unlock(f->lock);
+
+                ret = schedule_timeout(ret);
+
+                spin_lock(f->lock);
+        }
+        __set_current_state(TASK_RUNNING);
         if (!list_empty(&cb.base.node))
                 list_del(&cb.base.node);
-        __set_current_state(TASK_RUNNING);
 
 out:
-        spin_unlock_irqrestore(f->lock, irq_flags);
+        spin_unlock(f->lock);
 
         vmw_seqno_waiter_remove(dev_priv);