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Date: Mon, 24 Jun 2013 20:39:31 +0200 From: Oleg Nesterov <oleg@...hat.com> To: Denys Vlasenko <dvlasenk@...hat.com> Cc: linux-kernel@...r.kernel.org Subject: Re: [PATCH] epoll_wait: fix EINTR leak On 06/24, Oleg Nesterov wrote: > > On 06/24, Denys Vlasenko wrote: > > > > Usage of EINTR is wrong. > > I agree, this is not nice. However "fix EINTR leak" doesn't look > accurate, -EINTR is fine as an error code. Just the syscall should > restart if possible. > > > --- a/fs/eventpoll.c > > +++ b/fs/eventpoll.c > > @@ -1598,7 +1598,7 @@ fetch_events: > > if (ep_events_available(ep) || timed_out) > > break; > > if (signal_pending(current)) { > > - res = -EINTR; > > + res = -ERESTARTNOHAND; > > This and other similar changes do look right. > > Say, sys_epoll_wait(). With this patch it can sleep, then return > ERESTARTNOHAND. > > And we restart it with the same timeout again. If you want to > make it restartable, you need ERESTART_RESTARTBLOCK and > do_restart_epoll_wait() which we do not have. > > See for example sys_poll() which implements this logic. But, to avoid the confusion, please note that this change won't make it restartable wrt SA_RESTART. But it will help PTRACE_ATTACH or PTRACE_INTERRUPT or other "spurious" signal. We simply can't do this because there is no way to update "timeout" later if the task actually returns to user-mode. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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