On Sat, Feb 11, 2023 at 07:13:44AM -0700, Jens Axboe wrote: > On 2/10/23 8:18?PM, Ming Lei wrote: > > On Fri, Feb 10, 2023 at 02:08:35PM -0800, Linus Torvalds wrote: > >> On Fri, Feb 10, 2023 at 1:51 PM Jens Axboe <axboe@xxxxxxxxx> wrote: > >>> > >>> Speaking of splice/io_uring, Ming posted this today: > >>> > >>> https://lore.kernel.org/io-uring/20230210153212.733006-1-ming.lei@xxxxxxxxxx/ > >> > >> Ugh. Some of that is really ugly. Both 'ignore_sig' and > >> 'ack_page_consuming' just look wrong. Pure random special cases. > >> > >> And that 'ignore_sig' is particularly ugly, since the only thing that > >> sets it also sets SPLICE_F_NONBLOCK. > >> > >> And the *only* thing that actually then checks that field is > >> 'splice_from_pipe_next()', where there are exactly two > >> signal_pending() checks that it adds to, and > >> > >> (a) the first one is to protect from endless loops > >> > >> (b) the second one is irrelevant when SPLICE_F_NONBLOCK is set > >> > >> So honestly, just NAK on that series. > >> > >> I think that instead of 'ignore_sig' (which shouldn't exist), that > >> first 'signal_pending()' check in splice_from_pipe_next() should just > >> be changed into a 'fatal_signal_pending()'. > > > > Good point, here the signal is often from task_work_add() called by > > io_uring. > > Usually you'd use task_sigpending() to distinguis the two, but > fatal_signal_pending() as Linus suggests would also work. The only > concern here is that since you'll be potentially blocking on waiting for > the pipe to be readable - if task does indeed have task_work pending and > that very task_work is the one that will ensure that the pipe is now > readable, then you're waiting condition will never be satisfied. The 2nd signal_pending() will break the loop to get task_work handled, so it is safe to only change the 1st one to fatal_signal_pending(). Thanks, Ming
