Re: [net PATCH v4 2/6] virtio_net: wrap rtnl_lock in test for calling with lock already held
From: David Miller <davem@davemloft.net>
Date: 2017-01-17 17:06:56
From: John Fastabend <john.fastabend@gmail.com> Date: Sun, 15 Jan 2017 15:59:47 -0800
quoted hunk ↗ jump to hunk
@@ -2358,7 +2371,10 @@ static void remove_vq_common(struct virtnet_info *vi) /* Free unused buffers in both send and recv, if any. */ free_unused_bufs(vi); - free_receive_bufs(vi); + if (rtnl_is_locked()) + _free_receive_bufs(vi); + else + free_receive_bufs(vi); free_receive_page_frags(vi);
This doesn't work. rtnl_is_locked() doesn't tell if _you_ own the mutex, it just says that someone does. So if we now execute this code without taking the RTNL lock just because some other thread of control holds it, we introduce a race.