On 11/28/2012 12:25 PM, Maarten Lankhorst wrote:
This requires changing the order in ttm_bo_cleanup_refs_or_queue to take the reservation first, as there is otherwise no race free way to take lru lock before fence_lock.
Signed-off-by: Maarten Lankhorst maarten.lankhorst@canonical.com
Technically I think it would be possible to avoid reserving in the case the bo is still busy, and re-checking for sync_obj presence once we have reserved (since we release the fence lock).
But that's an optimization. The important thing at this point is to get this right.
Reviewed-by: Thomas Hellstrom thellstrom@vmware.com
drivers/gpu/drm/ttm/ttm_bo.c | 31 +++++++++++-------------------- drivers/gpu/drm/ttm/ttm_execbuf_util.c | 4 ++-- 2 files changed, 13 insertions(+), 22 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c index 7426fe5..202fc20 100644 --- a/drivers/gpu/drm/ttm/ttm_bo.c +++ b/drivers/gpu/drm/ttm/ttm_bo.c @@ -500,27 +500,17 @@ static void ttm_bo_cleanup_refs_or_queue(struct ttm_buffer_object *bo) { struct ttm_bo_device *bdev = bo->bdev; struct ttm_bo_global *glob = bo->glob;
- struct ttm_bo_driver *driver;
struct ttm_bo_driver *driver = bdev->driver; void *sync_obj = NULL; int put_count; int ret;
spin_lock(&glob->lru_lock);
ret = ttm_bo_reserve_locked(bo, false, true, false, 0);
spin_lock(&bdev->fence_lock); (void) ttm_bo_wait(bo, false, false, true);
- if (!bo->sync_obj) {
spin_lock(&glob->lru_lock);/*** Lock inversion between bo:reserve and bdev::fence_lock here,* but that's OK, since we're only trylocking.*/ret = ttm_bo_reserve_locked(bo, false, true, false, 0);if (unlikely(ret == -EBUSY))goto queue;
- if (!ret && !bo->sync_obj) { spin_unlock(&bdev->fence_lock); put_count = ttm_bo_del_from_lru(bo);
@@ -530,18 +520,19 @@ static void ttm_bo_cleanup_refs_or_queue(struct ttm_buffer_object *bo) ttm_bo_list_ref_sub(bo, put_count, true);
return;
- } else {
spin_lock(&glob->lru_lock);-queue:
- driver = bdev->driver; if (bo->sync_obj) sync_obj = driver->sync_obj_ref(bo->sync_obj);
spin_unlock(&bdev->fence_lock);
if (!ret) {
atomic_set(&bo->reserved, 0);wake_up_all(&bo->event_queue);}
kref_get(&bo->list_kref); list_add_tail(&bo->ddestroy, &bdev->ddestroy); spin_unlock(&glob->lru_lock);
spin_unlock(&bdev->fence_lock);
if (sync_obj) { driver->sync_obj_flush(sync_obj);
diff --git a/drivers/gpu/drm/ttm/ttm_execbuf_util.c b/drivers/gpu/drm/ttm/ttm_execbuf_util.c index 1986d00..cd9e452 100644 --- a/drivers/gpu/drm/ttm/ttm_execbuf_util.c +++ b/drivers/gpu/drm/ttm/ttm_execbuf_util.c @@ -213,8 +213,8 @@ void ttm_eu_fence_buffer_objects(struct list_head *list, void *sync_obj) driver = bdev->driver; glob = bo->glob;
- spin_lock(&bdev->fence_lock); spin_lock(&glob->lru_lock);
spin_lock(&bdev->fence_lock);
list_for_each_entry(entry, list, head) { bo = entry->bo;
@@ -223,8 +223,8 @@ void ttm_eu_fence_buffer_objects(struct list_head *list, void *sync_obj) ttm_bo_unreserve_locked(bo); entry->reserved = false; }
- spin_unlock(&glob->lru_lock); spin_unlock(&bdev->fence_lock);
spin_unlock(&glob->lru_lock);
list_for_each_entry(entry, list, head) { if (entry->old_sync_obj)