From 9c51ba1db37cab780f38b2210913959f22d7b830 Mon Sep 17 00:00:00 2001
From: Thomas Hellstrom <thellstrom@vmware.com>
Date: Wed, 2 Dec 2009 18:33:46 +0100
Subject: [PATCH] drm/ttm: Fix potential ttm_mem_evict_first races.
1) The function was previously called with a potentially empty
LRU list which would have lead to an OOPS or servere corruption.
2) In rare cases, after reservation has succeeded, another process may
already have evicted it or even pinned it. We must revalidate the
buffer status after releasing the lru lock.
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
---
drivers/gpu/drm/ttm/ttm_bo.c | 36 +++++++++++++++++++++++++++++++-----
1 file changed, 31 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index 7927fe99d0170..826240d4d675d 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -685,19 +685,45 @@ static int ttm_mem_evict_first(struct ttm_bo_device *bdev,
struct ttm_buffer_object *bo;
int ret, put_count = 0;
+retry:
spin_lock(&glob->lru_lock);
+ if (list_empty(&man->lru)) {
+ spin_unlock(&glob->lru_lock);
+ return -EBUSY;
+ }
+
bo = list_first_entry(&man->lru, struct ttm_buffer_object, lru);
kref_get(&bo->list_kref);
- ret = ttm_bo_reserve_locked(bo, interruptible, no_wait, false, 0);
- if (likely(ret == 0))
- put_count = ttm_bo_del_from_lru(bo);
+
+ ret = ttm_bo_reserve_locked(bo, false, true, false, 0);
+
+ if (unlikely(ret == -EBUSY)) {
+ spin_unlock(&glob->lru_lock);
+ if (likely(!no_wait))
+ ret = ttm_bo_wait_unreserved(bo, interruptible);
+
+ kref_put(&bo->list_kref, ttm_bo_release_list);
+
+ /**
+ * We *need* to retry after releasing the lru lock.
+ */
+
+ if (unlikely(ret != 0))
+ return ret;
+ goto retry;
+ }
+
+ put_count = ttm_bo_del_from_lru(bo);
spin_unlock(&glob->lru_lock);
- if (unlikely(ret != 0))
- return ret;
+
+ BUG_ON(ret != 0);
+
while (put_count--)
kref_put(&bo->list_kref, ttm_bo_ref_bug);
+
ret = ttm_bo_evict(bo, interruptible, no_wait);
ttm_bo_unreserve(bo);
+
kref_put(&bo->list_kref, ttm_bo_release_list);
return ret;
}
--
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