dma-buf/sw_sync: clean up list before signaling the fence
authorGustavo Padovan <gustavo.padovan@collabora.com>
Sat, 29 Jul 2017 15:22:16 +0000 (12:22 -0300)
committerGustavo Padovan <gustavo.padovan@collabora.com>
Mon, 31 Jul 2017 17:11:15 +0000 (14:11 -0300)
commit3792b7c1a70815fe4e954221c096f9278638fd21
tree4bbd50bc1eaa3e450f3258d78f64dccc735064a4
parent150b6a9d7d6fffb95c0a5349960a10569e8218b5
dma-buf/sw_sync: clean up list before signaling the fence

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 and
thus try to hold the lock to remove the fence from the list.

dma_fence_is_signaled_locked() tries to release/free the fence and hold
the lock in the process.

We fix that by changing the order operation and clean up the list and
rb-tree first.

v2: Drop fence get/put dance and manipulate the list first (Chris Wilson)

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20170729152217.8362-2-gustavo@padovan.org
drivers/dma-buf/sw_sync.c