drm/i915: Defer reporting EIO until we try to use the GPU

Instead of reporting EIO upfront in the entrance of an ioctl that may or
may not attempt to use the GPU, defer the actual detection of an invalid
ioctl to when we issue a GPU instruction. This allows us to continue to
use bo in video memory (via pread/pwrite and mmap) after the GPU has hung.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 14 insertions, 22 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index b9d4de3..52dd77b 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -75,8 +75,8 @@ static void i915_gem_info_remove_obj(struct drm_i915_private *dev_priv,
 	dev_priv->mm.object_memory -= size;
 }
 
-int
-i915_gem_check_is_wedged(struct drm_device *dev)
+static int
+i915_gem_wait_for_error(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct completion *x = &dev_priv->error_completion;
@@ -90,27 +90,24 @@ i915_gem_check_is_wedged(struct drm_device *dev)
 	if (ret)
 		return ret;
 
-	/* Success, we reset the GPU! */
-	if (!atomic_read(&dev_priv->mm.wedged))
-		return 0;
-
-	/* GPU is hung, bump the completion count to account for
-	 * the token we just consumed so that we never hit zero and
-	 * end up waiting upon a subsequent completion event that
-	 * will never happen.
-	 */
-	spin_lock_irqsave(&x->wait.lock, flags);
-	x->done++;
-	spin_unlock_irqrestore(&x->wait.lock, flags);
-	return -EIO;
+	if (atomic_read(&dev_priv->mm.wedged)) {
+		/* GPU is hung, bump the completion count to account for
+		 * the token we just consumed so that we never hit zero and
+		 * end up waiting upon a subsequent completion event that
+		 * will never happen.
+		 */
+		spin_lock_irqsave(&x->wait.lock, flags);
+		x->done++;
+		spin_unlock_irqrestore(&x->wait.lock, flags);
+	}
+	return 0;
 }
 
 int i915_mutex_lock_interruptible(struct drm_device *dev)
 {
-	struct drm_i915_private *dev_priv = dev->dev_private;
 	int ret;
 
-	ret = i915_gem_check_is_wedged(dev);
+	ret = i915_gem_wait_for_error(dev);
 	if (ret)
 		return ret;
 
@@ -118,11 +115,6 @@ int i915_mutex_lock_interruptible(struct drm_device *dev)
 	if (ret)
 		return ret;
 
-	if (atomic_read(&dev_priv->mm.wedged)) {
-		mutex_unlock(&dev->struct_mutex);
-		return -EAGAIN;
-	}
-
 	WARN_ON(i915_verify_lists(dev));
 	return 0;
 }