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 <thellstrom@vmware.com> Signed-off-by: Dave Airlie <airlied@redhat.com>
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@ -580,6 +580,7 @@ retry:
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if (unlikely(ret != 0))
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return ret;
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retry_reserve:
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spin_lock(&glob->lru_lock);
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if (unlikely(list_empty(&bo->ddestroy))) {
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@ -587,14 +588,20 @@ retry:
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return 0;
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}
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ret = ttm_bo_reserve_locked(bo, interruptible,
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no_wait_reserve, false, 0);
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ret = ttm_bo_reserve_locked(bo, false, true, false, 0);
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if (unlikely(ret != 0)) {
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if (unlikely(ret == -EBUSY)) {
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spin_unlock(&glob->lru_lock);
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return ret;
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if (likely(!no_wait_reserve))
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ret = ttm_bo_wait_unreserved(bo, interruptible);
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if (unlikely(ret != 0))
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return ret;
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goto retry_reserve;
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}
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BUG_ON(ret != 0);
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/**
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* We can re-check for sync object without taking
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* the bo::lock since setting the sync object requires
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@ -811,10 +818,7 @@ retry:
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no_wait_reserve, no_wait_gpu);
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kref_put(&bo->list_kref, ttm_bo_release_list);
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if (likely(ret == 0 || ret == -ERESTARTSYS))
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return ret;
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goto retry;
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return ret;
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}
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ret = ttm_bo_reserve_locked(bo, false, true, false, 0);
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