From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/6694 Path: news.gmane.org!not-for-mail From: Rich Felker Newsgroups: gmane.linux.lib.musl.general Subject: Re: [RFC] EINTR and PC loser-ing library design Date: Mon, 8 Dec 2014 10:09:54 -0500 Message-ID: <20141208150954.GE4574@brightrain.aerifal.cx> References: <20141208141039.GA4574@brightrain.aerifal.cx> <5485B5E1.90602@skarnet.org> <20141208143223.GB4574@brightrain.aerifal.cx> <5485B98D.4010603@skarnet.org> <20141208150031.GD4574@brightrain.aerifal.cx> Reply-To: musl@lists.openwall.com NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: ger.gmane.org 1418051416 29730 80.91.229.3 (8 Dec 2014 15:10:16 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 8 Dec 2014 15:10:16 +0000 (UTC) To: musl@lists.openwall.com Original-X-From: musl-return-6707-gllmg-musl=m.gmane.org@lists.openwall.com Mon Dec 08 16:10:09 2014 Return-path: Envelope-to: gllmg-musl@m.gmane.org Original-Received: from mother.openwall.net ([195.42.179.200]) by plane.gmane.org with smtp (Exim 4.69) (envelope-from ) id 1Xxzwv-000099-Cz for gllmg-musl@m.gmane.org; Mon, 08 Dec 2014 16:10:09 +0100 Original-Received: (qmail 16138 invoked by uid 550); 8 Dec 2014 15:10:07 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: Original-Received: (qmail 16125 invoked from network); 8 Dec 2014 15:10:06 -0000 Content-Disposition: inline In-Reply-To: <20141208150031.GD4574@brightrain.aerifal.cx> User-Agent: Mutt/1.5.21 (2010-09-15) Original-Sender: Rich Felker Xref: news.gmane.org gmane.linux.lib.musl.general:6694 Archived-At: On Mon, Dec 08, 2014 at 10:00:31AM -0500, Rich Felker wrote: > On Mon, Dec 08, 2014 at 03:45:33PM +0100, Laurent Bercot wrote: > > On 08/12/2014 15:32, Rich Felker wrote: > > > > >The system call restarts (or, formally, it's as if it were never > > >interrupted; EINTR only applies to signal _handlers_). > > > > Could you please provide a pointer to the specification that > > guarantees this ? I've never been able to find a normative text that > > ensures you will never get EINTR unless you explicitly install a > > signal handler without SA_RESTART. > > I've had a hard time pinning it down too, but that's what all modern > (e.g. modern enough to have a working sigaction) implementations do, > and it's the obviously correct behavior. I would consider making a > request for clarification here, but after what happened with the C > locale issue, I'd kinda fear some trolls would appear and insist that > EINTR be allowed to happen for no good reason. :( The closest I can find is XSH 2.4.4 Signal Effects on Other Functions: Signals affect the behavior of certain functions defined by this volume of POSIX.1-2008 if delivered to a process while it is executing such a function. If the action of the signal is to terminate the process, the process shall be terminated and the function shall not return. If the action of the signal is to stop the process, the process shall stop until continued or terminated. Generation of a SIGCONT signal for the process shall cause the process to be continued, and the original function shall continue at the point the process was stopped. If the action of the signal is to invoke a signal-catching function, the signal-catching function shall be invoked; in this case the original function is said to be "interrupted" by the signal. If the signal-catching function executes a return statement, the behavior of the interrupted function shall be as described individually for that function, except as noted for unsafe functions. Signals that are ignored shall not affect the behavior of any function; signals that are blocked shall not affect the behavior of any function until they are unblocked and then delivered, except as specified for the sigpending() and sigwait() functions. The above text seems to be what defines the concept of "interrupted", and it's in terms of a "signal-catching function". The behavior "as described individually for that function" is usually to fail with EINTR, but it's overridden by the text of the sigaction function which defines SA_RESTART to automatically restart functions interrupted in this sense. Rich