drm/nouveau: call ttm_bo_wait with the bo lock held to prevent hang

nouveau_gem_ioctl_cpu_prep calls ttm_bo_wait without the bo lock held.
ttm_bo_wait unlocks that lock, and so must be called with it held.

Currently this bug causes libdrm nouveau_bo_busy() to hang the machine.

Signed-off-by: Luca Barbieri <luca at luca-barbieri.com>
Acked-by: Maarten Maathuis <madman2003@gmail.com>
Signed-off-by: Francisco Jerez <currojerez@riseup.net>
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 6ac804b0c9f9..70cc30803e3b 100644
--- a/drivers/gpu/drm/nouveau/nouveau_gem.c
+++ b/drivers/gpu/drm/nouveau/nouveau_gem.c
@@ -925,7 +925,9 @@ nouveau_gem_ioctl_cpu_prep(struct drm_device *dev, void *data,
         }
 
         if (req->flags & NOUVEAU_GEM_CPU_PREP_NOBLOCK) {
+                spin_lock(&nvbo->bo.lock);
                 ret = ttm_bo_wait(&nvbo->bo, false, false, no_wait);
+                spin_unlock(&nvbo->bo.lock);
         } else {
                 ret = ttm_bo_synccpu_write_grab(&nvbo->bo, no_wait);
                 if (ret == 0)