drm/msm: fix potential deadlock in gpu init

Somewhere along the way, the firmware loader sprouted another lock
dependency, resulting in possible deadlock scenario:

 &dev->struct_mutex --> &sb->s_type->i_mutex_key#2 --> &mm->mmap_sem

which is problematic vs things like gem mmap.

So introduce a separate mutex to synchronize gpu init.

Signed-off-by: Rob Clark <robdclark@gmail.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
index 915240b4b80a..4a0dce587745 100644
--- a/drivers/gpu/drm/msm/msm_gpu.c
+++ b/drivers/gpu/drm/msm/msm_gpu.c
@@ -612,8 +612,11 @@ int msm_gpu_init(struct drm_device *drm, struct platform_device *pdev,
         }
         gpu->id = msm_register_mmu(drm, gpu->mmu);
 
+
         /* Create ringbuffer: */
+        mutex_lock(&drm->struct_mutex);
         gpu->rb = msm_ringbuffer_new(gpu, ringsz);
+        mutex_unlock(&drm->struct_mutex);
         if (IS_ERR(gpu->rb)) {
                 ret = PTR_ERR(gpu->rb);
                 gpu->rb = NULL;