From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B646DC282DD for ; Thu, 23 May 2019 16:36:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 952C321019 for ; Thu, 23 May 2019 16:36:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731155AbfEWQgW (ORCPT ); Thu, 23 May 2019 12:36:22 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56428 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730752AbfEWQgV (ORCPT ); Thu, 23 May 2019 12:36:21 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 1484A308624A; Thu, 23 May 2019 16:36:11 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.159]) by smtp.corp.redhat.com (Postfix) with SMTP id 0D76C60C9E; Thu, 23 May 2019 16:36:07 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Thu, 23 May 2019 18:36:08 +0200 (CEST) Date: Thu, 23 May 2019 18:36:04 +0200 From: Oleg Nesterov To: David Laight Cc: 'Deepa Dinamani' , Linux Kernel Mailing List , Andrew Morton , Alexander Viro , Arnd Bergmann , "dbueso@suse.de" , "axboe@kernel.dk" , Davidlohr Bueso , Eric Wong , Jason Baron , Linux FS-devel Mailing List , linux-aio , Omar Kilani , Thomas Gleixner , "stable@vger.kernel.org" Subject: Re: [PATCH v2] signal: Adjust error codes according to restore_user_sigmask() Message-ID: <20190523163604.GE23070@redhat.com> References: <20190522032144.10995-1-deepa.kernel@gmail.com> <20190522150505.GA4915@redhat.com> <20190522161407.GB4915@redhat.com> <4f7b6dbeab1d424baaebd7a5df116349@AcuMS.aculab.com> <20190523145944.GB23070@redhat.com> <345cfba5edde470f9a68d913f44fa342@AcuMS.aculab.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <345cfba5edde470f9a68d913f44fa342@AcuMS.aculab.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Thu, 23 May 2019 16:36:21 +0000 (UTC) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 05/23, David Laight wrote: > > From: Oleg Nesterov > > On 05/23, David Laight wrote: > > > > > > I'm confused... > > > > Me too. To clarify, the current code is obviously buggy, pselect/whatever > > shouldn't return 0 (or anything else) if it was interrupted and we are going > > to deliver the signal. > > If it was interrupted the return value has to be EINTR. Yes, and this is what we need to fix. > Whether any signal handlers are called is a separate matter. Not really... because in this case we know that the signal will be delivered, > > Not sure I understand... OK, suppose that you do > > > > block-all-signals; > > ret = pselect(..., sigmask(SIG_URG)); > > > > if it returns success/timeout then the handler for SIG_URG should not be called? > > Ugg... > Posix probably allows the signal handler be called at the point the event > happens rather than being deferred until the system call completes. > Queueing up the signal handler to be run at a later time (syscall exit) > certainly makes sense. > Definitely safest to call the signal handler even if success/timeout > is returned. Why? > pselect() exists to stop the entry race, not the exit one. pselect() has to block SIG_URG again before it returns to user-mode, right? Suppose pselect() finds a ready fd, and this races with SIG_URG. Why do you think the handler should run? What if SIG_URG comes right after pselect() blocks SIG_URG again? I mean, how this differs the case when it comes before, but a ready fd was already found? Oleg.