drm/nouveau: drop drm_global_mutex before sleeping in submission path

If we keep hold of the mutex here, the process which currently holds the
buffer object will never be able to release it, causing a deadlock.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/gpu/drm/nouveau/nouveau_gem.c b/drivers/gpu/drm/nouveau/nouveau_gem.c
index 613f878e6d0f..93711dfcafc1 100644
--- a/drivers/gpu/drm/nouveau/nouveau_gem.c
+++ b/drivers/gpu/drm/nouveau/nouveau_gem.c
@@ -337,7 +337,9 @@ retry:
                                 return -EINVAL;
                         }
 
+                        mutex_unlock(&drm_global_mutex);
                         ret = ttm_bo_wait_cpu(&nvbo->bo, false);
+                        mutex_lock(&drm_global_mutex);
                         if (ret) {
                                 NV_ERROR(dev, "fail wait_cpu\n");
                                 return ret;