[PATCH] drm/radeon: fix virtual memory locking in case of reset

[j.glisse at gmail.com]

From: Jerome Glisse <jglisse at redhat.com>

Lock/unlock mutex in proper order to avoid deadlock in case
of GPU reset triggered from VM code path.

Cc: stable at vger.kernel.org [3.5]
Signed-off-by: Jerome Glisse <jglisse at redhat.com>
---
 drivers/gpu/drm/radeon/radeon_gart.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/radeon/radeon_gart.c b/drivers/gpu/drm/radeon/radeon_gart.c
index b372005..7eabb59 100644
--- a/drivers/gpu/drm/radeon/radeon_gart.c
+++ b/drivers/gpu/drm/radeon/radeon_gart.c
@@ -508,14 +508,19 @@ static void radeon_vm_unbind_locked(struct radeon_device *rdev,
 	while (vm->fence) {
 		int r;
 		r = radeon_fence_wait(vm->fence, false);
-		if (r)
+		if (r) {
 			DRM_ERROR("error while waiting for fence: %d\n", r);
+		}
 		if (r == -EDEADLK) {
+			/* release mutex and lock in right order */
 			mutex_unlock(&rdev->vm_manager.lock);
+			mutex_unlock(&vm->mutex);
 			r = radeon_gpu_reset(rdev);
 			mutex_lock(&rdev->vm_manager.lock);
-			if (!r)
+			mutex_lock(&vm->mutex);
+			if (!r) {
 				continue;
+			}
 		}
 		break;
 	}
@@ -551,7 +556,9 @@ void radeon_vm_manager_fini(struct radeon_device *rdev)
 	mutex_lock(&rdev->vm_manager.lock);
 	/* unbind all active vm */
 	list_for_each_entry_safe(vm, tmp, &rdev->vm_manager.lru_vm, list) {
+		mutex_lock(&vm->mutex);
 		radeon_vm_unbind_locked(rdev, vm);
+		mutex_unlock(&vm->mutex);
 	}
 	rdev->vm_manager.funcs->fini(rdev);
 	mutex_unlock(&rdev->vm_manager.lock);
-- 
1.7.10.4