Commit b8e902f2 authored by Thomas Hellstrom's avatar Thomas Hellstrom Committed by Dave Airlie

drm/ttm: Fix a theoretical race in ttm_bo_cleanup_refs()

In theory, that function could release the lru lock between
checking for bo on ddestroy list and a successful reserve if the bo
was already reserved, and the function was called with waiting reserves
However, all current reservers of a bo on the ddestroy list would
atomically take the bo off the list after a successful reserve so this
race should not have been hit, so no need to backport for stable.

This patch also fixes a case found by Maarten Lankhorst where
ttm_mem_evict_first called with no_wait_gpu would incorrectly
spin waiting for bo idle if trying to evict a busy buffer that
also sits on the ddestroy list.
Signed-off-by: default avatarThomas Hellstrom <>
Signed-off-by: default avatarDave Airlie <>
parent 7bc17a78
......@@ -580,6 +580,7 @@ retry:
if (unlikely(ret != 0))
return ret;
if (unlikely(list_empty(&bo->ddestroy))) {
......@@ -587,14 +588,20 @@ retry:
return 0;
ret = ttm_bo_reserve_locked(bo, interruptible,
no_wait_reserve, false, 0);
ret = ttm_bo_reserve_locked(bo, false, true, false, 0);
if (unlikely(ret != 0)) {
if (unlikely(ret == -EBUSY)) {
return ret;
if (likely(!no_wait_reserve))
ret = ttm_bo_wait_unreserved(bo, interruptible);
if (unlikely(ret != 0))
return ret;
goto retry_reserve;
BUG_ON(ret != 0);
* We can re-check for sync object without taking
* the bo::lock since setting the sync object requires
......@@ -811,10 +818,7 @@ retry:
no_wait_reserve, no_wait_gpu);
kref_put(&bo->list_kref, ttm_bo_release_list);
if (likely(ret == 0 || ret == -ERESTARTSYS))
return ret;
goto retry;
return ret;
ret = ttm_bo_reserve_locked(bo, false, true, false, 0);
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