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

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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 <thellstrom@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
This commit is contained in:
Thomas Hellstrom 2012-10-22 12:51:26 +00:00 committed by Dave Airlie
parent 7bc17a7837
commit b8e902f24f
1 changed files with 12 additions and 8 deletions
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20
drivers/gpu/drm/ttm/ttm_bo.c
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@ -580,6 +580,7 @@ retry:
if (unlikely(ret != 0)) if (unlikely(ret != 0))
return ret; return ret;
retry_reserve:
spin_lock(&glob->lru_lock); spin_lock(&glob->lru_lock);
if (unlikely(list_empty(&bo->ddestroy))) { if (unlikely(list_empty(&bo->ddestroy))) {
@ -587,14 +588,20 @@ retry:
return 0; return 0;
} }
ret = ttm_bo_reserve_locked(bo, interruptible, ret = ttm_bo_reserve_locked(bo, false, true, false, 0);
no_wait_reserve, false, 0);
if (unlikely(ret != 0)) { if (unlikely(ret == -EBUSY)) {
spin_unlock(&glob->lru_lock); 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 * We can re-check for sync object without taking
* the bo::lock since setting the sync object requires * the bo::lock since setting the sync object requires
@ -811,10 +818,7 @@ retry:
no_wait_reserve, no_wait_gpu); no_wait_reserve, no_wait_gpu);
kref_put(&bo->list_kref, ttm_bo_release_list); kref_put(&bo->list_kref, ttm_bo_release_list);
if (likely(ret == 0 || ret == -ERESTARTSYS)) return ret;
return ret;
goto retry;
} }
ret = ttm_bo_reserve_locked(bo, false, true, false, 0); ret = ttm_bo_reserve_locked(bo, false, true, false, 0);