From b8e902f24fdd16c4373ddc37a4e150c4afe9c6db Mon Sep 17 00:00:00 2001 From: Thomas Hellstrom Date: Mon, 22 Oct 2012 12:51:26 +0000 Subject: [PATCH] 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 allowed. 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: Thomas Hellstrom Signed-off-by: Dave Airlie --- drivers/gpu/drm/ttm/ttm_bo.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c index d42631cade5a..bf6e4b5a73b5 100644 --- a/drivers/gpu/drm/ttm/ttm_bo.c +++ b/drivers/gpu/drm/ttm/ttm_bo.c @@ -580,6 +580,7 @@ retry: if (unlikely(ret != 0)) return ret; +retry_reserve: spin_lock(&glob->lru_lock); 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)) { spin_unlock(&glob->lru_lock); - 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); -- 2.34.1