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@xxxxxxxxxxxxx>
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@xxxxxxxxxx>
---
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)
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