On Thu, Jul 27, 2017 at 04:03:53PM -0300, Gustavo Padovan wrote:
From: Gustavo Padovan gustavo.padovan@collabora.com
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@chris-wilson.co.uk Signed-off-by: Gustavo Padovan gustavo.padovan@collabora.com
Do we have a testcase for this? -Daniel
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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