From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758332AbXEUFFl (ORCPT ); Mon, 21 May 2007 01:05:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753152AbXEUFFf (ORCPT ); Mon, 21 May 2007 01:05:35 -0400 Received: from x35.xmailserver.org ([64.71.152.41]:4339 "EHLO x35.xmailserver.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754338AbXEUFFe (ORCPT ); Mon, 21 May 2007 01:05:34 -0400 X-AuthUser: davidel@xmailserver.org Date: Sun, 20 May 2007 22:05:00 -0700 (PDT) From: Davide Libenzi X-X-Sender: davide@alien.or.mcafeemobile.com To: Andrew Morton cc: Davi Arnaut , Linus Torvalds , Linux Kernel Mailing List Subject: Re: [PATCH] signalfd: retrieve multiple signals with one read() call In-Reply-To: <20070520212627.398ffd23.akpm@linux-foundation.org> Message-ID: References: <464F912F.3040205@haxent.com.br> <20070520210210.9a895eec.akpm@linux-foundation.org> <20070520212627.398ffd23.akpm@linux-foundation.org> X-GPG-FINGRPRINT: CFAE 5BEE FD36 F65E E640 56FE 0974 BF23 270F 474E X-GPG-PUBLIC_KEY: http://www.xmailserver.org/davidel.asc MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 20 May 2007, Andrew Morton wrote: > > I think it fits the rule "buffer must be big enough for at least one sigingo". > > We use the special return 0; as indicator that the process we were > > monitoring signals, detached the sighand. > > > > hm. Kernel violates proper read() semantics in many places. Looks like we > just did it again. I think we can have the check that "if size == 0 return 0". The above cited return-0-on-detch would still apply for enough sized buffers. So: 1) size == 0, return 0 (POSIX wants this) 2) size < sizeof(signalfd_siginfo), return EINVAL 3) size >= sizeof(signalfd_siginfo) && DETACH, return 0 The signalfd falls into what POSIX defined as "special file", and can return a lower-than-size result. > Unless we just remove the __clear_user() altogether. Who said that "Unused > memebers should be zero"? Because it is a typically used value for still-unused/reserved members? Better than random values I think ;) Members validity is driven by si_code & SI_MASK anyway. - Davide