From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxx>
If userspace already dropped its own reference by closing the sw_sync
fence fd we might end up in a deadlock where
dma_fence_is_signaled_locked() will trigger the release of the fence a
thus try to hold the lock to remove the fence from the list.
We need to grab a reference to the fence before calling into this chain if
we want to avoid this issue.
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxx>
---
drivers/dma-buf/sw_sync.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/dma-buf/sw_sync.c b/drivers/dma-buf/sw_sync.c
index af1bc84..8291434 100644
--- a/drivers/dma-buf/sw_sync.c
+++ b/drivers/dma-buf/sw_sync.c
@@ -144,11 +144,16 @@ static void sync_timeline_signal(struct sync_timeline *obj, unsigned int inc)
obj->value += inc;
list_for_each_entry_safe(pt, next, &obj->pt_list, link) {
- if (!dma_fence_is_signaled_locked(&pt->base))
+ dma_fence_get(&pt->base);
+ if (!dma_fence_is_signaled_locked(&pt->base)) {
+ dma_fence_put(&pt->base);
break;
+ }
list_del_init(&pt->link);
rb_erase(&pt->node, &obj->pt_tree);
+
+ dma_fence_put(&pt->base);
}
spin_unlock_irq(&obj->lock);
--
2.9.4
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