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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 AB7C9C31E45 for ; Thu, 13 Jun 2019 16:01:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8B2B220679 for ; Thu, 13 Jun 2019 16:01:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390567AbfFMQBC convert rfc822-to-8bit (ORCPT ); Thu, 13 Jun 2019 12:01:02 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([146.101.78.151]:44498 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731454AbfFMIsr (ORCPT ); Thu, 13 Jun 2019 04:48:47 -0400 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-77-sMo5MtksNjyrgFaEIWzQmA-1; Thu, 13 Jun 2019 09:48:42 +0100 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b::d117) by AcuMS.aculab.com (fd9f:af1c:a25b::d117) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Thu, 13 Jun 2019 09:48:41 +0100 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Thu, 13 Jun 2019 09:48:41 +0100 From: David Laight To: 'Oleg Nesterov' CC: "'Eric W. Biederman'" , 'Andrew Morton' , 'Deepa Dinamani' , "'linux-kernel@vger.kernel.org'" , "'arnd@arndb.de'" , "'dbueso@suse.de'" , "'axboe@kernel.dk'" , "'dave@stgolabs.net'" , "'e@80x24.org'" , "'jbaron@akamai.com'" , "'linux-fsdevel@vger.kernel.org'" , "'linux-aio@kvack.org'" , "'omar.kilani@gmail.com'" , "'tglx@linutronix.de'" , 'Al Viro' , 'Linus Torvalds' , "'linux-arch@vger.kernel.org'" Subject: RE: [RFC PATCH 1/5] signal: Teach sigsuspend to use set_user_sigmask Thread-Topic: [RFC PATCH 1/5] signal: Teach sigsuspend to use set_user_sigmask Thread-Index: AQHVH9JWknGdQ9+D0UeylJNmvFzQKKaWJ31QgAHScICAABPkMIABOuaw Date: Thu, 13 Jun 2019 08:48:41 +0000 Message-ID: <6e9b964b08d84c99980b1707e5fe3d1d@AcuMS.aculab.com> References: <20190522032144.10995-1-deepa.kernel@gmail.com> <20190529161157.GA27659@redhat.com> <20190604134117.GA29963@redhat.com> <20190606140814.GA13440@redhat.com> <87k1dxaxcl.fsf_-_@xmission.com> <87ef45axa4.fsf_-_@xmission.com> <20190610162244.GB8127@redhat.com> <87lfy96sta.fsf@xmission.com> <9199239a450d4ea397783ccf98742220@AcuMS.aculab.com> <20190612134558.GB3276@redhat.com> <6f748b26bef748208e2a74174c0c0bfc@AcuMS.aculab.com> In-Reply-To: <6f748b26bef748208e2a74174c0c0bfc@AcuMS.aculab.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-MC-Unique: sMo5MtksNjyrgFaEIWzQmA-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: David Laight > Sent: 12 June 2019 15:18 > From: Oleg Nesterov > > Sent: 12 June 2019 14:46 > > On 06/11, David Laight wrote: > > > > > > If I have an application that has a loop with a pselect call that > > > enables SIGINT (without a handler) and, for whatever reason, > > > one of the fd is always 'ready' then I'd expect a SIGINT > > > (from ^C) to terminate the program. > > > > This was never true. > > > > Before Eric's patches SIGINT can kill a process or not, depending on timing. > > In particular, if SIGINT was already pending before pselect() and it finds > > an already ready fd, the program won't terminate. > > Which matches what I see on a very old Linux system. > > > After the Eric's patches SIGINT will only kill the program if pselect() does > > not find a ready fd. > > > > And this is much more consistent. Now we can simply say that the signal will > > be delivered only if pselect() fails and returns -EINTR. If it doesn't have > > a handler the process will be killed, otherwise the handler will be called. > > But is it what the standards mandate? > Can anyone check how Solaris and any of the BSDs behave? > I don't have access to any solaris systems (I doubt I'll get the disk to > spin on the one in my garage). > I can check NetBSD when I get home. I tested NetBSD last night. pselect() always calls the signal handlers even when an fd is ready. I'm beginning to suspect that this is the 'standards conforming' behaviour. I don't remember when pselect() was added to the ToG specs, it didn't go through XNET while I was going to the meetings. David > > The ToG page for pselect() http://pubs.opengroup.org/onlinepubs/9699919799/functions/pselect.html > says: > "If sigmask is not a null pointer, then the pselect() function shall replace > the signal mask of the caller by the set of signals pointed to by sigmask > before examining the descriptors, and shall restore the signal mask of the > calling thread before returning." > Note that it says 'before examining the descriptors' not 'before blocking'. > Under the general description about signals it also says that the signal handler > will be called (or other action happen) when a pending signal is unblocked. > So unblocking SIGINT (set to SIG_DFL) prior to examining the descriptors > should be enough to cause the process to exit. > The fact that signal handlers are not called until 'return to user' > is really an implementation choice - but (IMHO) it should appear as if they > were called at the time they became unmasked. > > If nothing else the man pages need a note about the standards and portability. > > David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)