drm/msm: move submit fence wait out of struct_mutex

Probably a symptom of needing finer grained locking, but if we wait on
the incoming fence-fd (which could come from a different context) while
holding struct_mutex, that blocks retire_worker so gpu fences cannot get
signalled.

This causes a problem if userspace manages to get more than a frame
ahead, leaving the atomic-commit worker blocked waiting on fences that
cannot be signaled because submit is blocked waiting for a fence
signalled from vblank (after the atomic commit which is blocked).

If we start having multiple fence ctxs for the gpu, submit_fence_sync()
would probably need to move outside of struct_mutex as well.

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

diff --git a/drivers/gpu/drm/msm/msm_gem_submit.c b/drivers/gpu/drm/msm/msm_gem_submit.c
index 1172fe7a9252c0828889ad1e95b17a02bae8fbf9..1c545ebe6a5a0f875a995b1db3a1204b0b21d57e 100644 (file)
--- a/drivers/gpu/drm/msm/msm_gem_submit.c
+++ b/drivers/gpu/drm/msm/msm_gem_submit.c
@@ -404,6 +404,24 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data,
        if (MSM_PIPE_FLAGS(args->flags) & ~MSM_SUBMIT_FLAGS)
                return -EINVAL;
 
+       if (args->flags & MSM_SUBMIT_FENCE_FD_IN) {
+               in_fence = sync_file_get_fence(args->fence_fd);
+
+               if (!in_fence)
+                       return -EINVAL;
+
+               /* TODO if we get an array-fence due to userspace merging multiple
+                * fences, we need a way to determine if all the backing fences
+                * are from our own context..
+                */
+
+               if (in_fence->context != gpu->fctx->context) {
+                       ret = dma_fence_wait(in_fence, true);
+                       if (ret)
+                               return ret;
+               }
+       }
+
        ret = mutex_lock_interruptible(&dev->struct_mutex);
        if (ret)
                return ret;
@@ -431,27 +449,6 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data,
        if (ret)
                goto out;
 
-       if (args->flags & MSM_SUBMIT_FENCE_FD_IN) {
-               in_fence = sync_file_get_fence(args->fence_fd);
-
-               if (!in_fence) {
-                       ret = -EINVAL;
-                       goto out;
-               }
-
-               /* TODO if we get an array-fence due to userspace merging multiple
-                * fences, we need a way to determine if all the backing fences
-                * are from our own context..
-                */
-
-               if (in_fence->context != gpu->fctx->context) {
-                       ret = dma_fence_wait(in_fence, true);
-                       if (ret)
-                               goto out;
-               }
-
-       }
-
        if (!(args->fence & MSM_SUBMIT_NO_IMPLICIT)) {
                ret = submit_fence_sync(submit);
                if (ret)