So, what should we do? On 2019/3/7 10:18, Al Viro wrote: > On Thu, Mar 07, 2019 at 12:03:10AM +0000, Al Viro wrote: >> From: Al Viro <v...@zeniv.linux.org.uk> >> >> In case of early wakeups, aio_poll() assumes that aio_poll_complete() >> has either already happened or is imminent. In that case we do not >> want to put iocb on the list of cancellables. However, ignored >> wakeups need to be treated as if wakeup has not happened at all. >> Trivially fixed by having aio_poll_wake() set ->woken only after >> it's committed to taking iocb out of the waitqueue. >> >> Spotted-by: zhengbin <zhengbi...@huawei.com> >> Signed-off-by: Al Viro <v...@zeniv.linux.org.uk> > > ... and unfortunately it's worse than just that - what both of us > have missed is that one could have non-specific wakep + schedule_work + > aio_poll_complete_work() rechecking ->poll(), seeing nothing of > interest and reinserting into queue. All before vfs_poll() manages > to return into aio_poll(). The window is harder to hit, but it's > still there, with exact same "failed to add to cancel list" kind of bug > if we do hit it ;-/ > > . >
