On 11/30/2017 03:50 PM, Andrew Morton wrote: > On Thu, 30 Nov 2017 06:20:35 -0800 Christoph Hellwig <hch@xxxxxx> wrote: > >> Hi all, >> >> this series adds a strategic lockdep_assert_held to __wake_up_common >> to ensure callers really do hold the wait_queue_head lock when calling >> the unlocked wake_up variants. It turns out epoll did not do this >> for a fairly common path (hit all the time by systemd during bootup), >> so the second patch fixed this instance as well. > > What are the runtime effects of the epoll bug? > I don't think there is a bug here. The 'wake_up_locked()' calls in epoll are being protected by the ep->lock, not the wait_queue_head lock. So arguably the 'annotation' is wrong, but I don't think there is a bug beyond that. Thanks, -Jason
