From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/9539 Path: news.gmane.org!not-for-mail From: Linus Torvalds Newsgroups: gmane.linux.kernel,gmane.linux.lib.musl.general Subject: Re: [musl] Re: [RFC PATCH] x86/vdso/32: Add AT_SYSINFO cancellation helpers Date: Wed, 9 Mar 2016 11:47:30 -0800 Message-ID: References: <06079088639eddd756e2092b735ce4a682081308.1457486598.git.luto@kernel.org> <20160309085631.GA3247@gmail.com> <20160309113449.GZ29662@port70.net> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-Trace: ger.gmane.org 1457552883 30305 80.91.229.3 (9 Mar 2016 19:48:03 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 9 Mar 2016 19:48:03 +0000 (UTC) To: Ingo Molnar , Andy Lutomirski , "the arch/x86 maintainers" , Linux Kernel Mailing List , Borislav Petkov , "musl@lists.openwall.com" , Linus Torvalds , Andrew Morton , Thomas Gleixner , Peter Zijlstra Original-X-From: linux-kernel-owner@vger.kernel.org Wed Mar 09 20:47:53 2016 Return-path: Envelope-to: glk-linux-kernel-3@plane.gmane.org Original-Received: from vger.kernel.org ([209.132.180.67]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1adk5G-0003Kk-TL for glk-linux-kernel-3@plane.gmane.org; Wed, 09 Mar 2016 20:47:51 +0100 Original-Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933859AbcCITrf (ORCPT ); Wed, 9 Mar 2016 14:47:35 -0500 Original-Received: from mail-ig0-f174.google.com ([209.85.213.174]:35829 "EHLO mail-ig0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753732AbcCITrb (ORCPT ); Wed, 9 Mar 2016 14:47:31 -0500 Original-Received: by mail-ig0-f174.google.com with SMTP id vf5so388718igb.0 for ; Wed, 09 Mar 2016 11:47:31 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:sender:in-reply-to:references:date:message-id:subject :from:to; bh=5+x/ydScIiaUybO9S0HyJO5bimzK5ZZMXaRypz6WwBU=; b=yLVsTSQeZsm9q4CJy/iX8l1sK3TDlDmPJ6Xhseq+dimmgk+tkQ7YlXU4UYizdI84PK XZRGNVkqQJKzJkuDMACQ5fJIbWXXGr/4JKiPrXNadPqul4RaNIxZ4gzTT0D+QKwEr221 WBD/xatelvf7TbyF3Y7ADzPAquzqAfbUb8bF4035adQ1FU+NwAFIjg8aiMbTN+nnV3hP xQbCnwAUDXY5lNrJGc4f3Ex1q1jfeu+MdRh9NTJ3LrXB4rq2JMcxjoR6Tkx2zivs8+Yd voL3s8hZIXIuW53lXOTQwHzgwjAQ8KQdEbgj5wXwvo/zWgnkynCO1zNx3SqCNPL+OwA6 b9DQ== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:sender:in-reply-to:references:date:message-id:subject :from:to; bh=5+x/ydScIiaUybO9S0HyJO5bimzK5ZZMXaRypz6WwBU=; b=LB95S+h2+ccYRIIcp4hIqFeK8WCMDuj9F2neCL1+xqrUzWkiyemv4bP+tCsrkItlF0 LQa28Ufnn39WGJabj0gAJra4RgCqAZVwB+cwljRq4MjoW1d2sf1EH+lStvYgOQjZG+nW JaFz3kMKosqOqpeLjBvVRonsXK+cLWKKadHzU= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:sender:in-reply-to:references:date :message-id:subject:from:to; bh=5+x/ydScIiaUybO9S0HyJO5bimzK5ZZMXaRypz6WwBU=; b=KPEx0ysBRhTMpsbhEdzywTtYsw2u0IMbRYOGEquWQal9il3YN/DyIef3B20Gz3JeCl 4Y+8OjKlCSJw145zIuV1uNQa2nNYFOAGMmZzk9ceO/xy5cGv4qEDkmjE6JQ7wAXUibvW lCnKm3BllpxiAz19hsv/fFs4ajQRwSDFJ3fDCexPC42zTv+SjCO9cmzLUxCRqqmkjtCt sBdsUAuWzSpm8zcT3x8X0J23bYtf7T6uhWaU0arHbYhmLekChrrZUYsXVf0BwjzYmUDp j7em8f1MUbt4ZR0afBtgL0IuPJeZ47CzC7Wccx7K+UYGuKKOjSFpSWflYCKIaI73KDCu Scew== X-Gm-Message-State: AD7BkJJ9OqqquIXszQ6N7y44xIqtd1rlR4LTmsTLqf8mz76DmZmOZ6QgPA3EjaP9IhBKA+ar1t4RV/ke9CKnIQ== X-Received: by 10.50.176.138 with SMTP id ci10mr26860310igc.93.1457552850526; Wed, 09 Mar 2016 11:47:30 -0800 (PST) Original-Received: by 10.36.93.202 with HTTP; Wed, 9 Mar 2016 11:47:30 -0800 (PST) In-Reply-To: <20160309113449.GZ29662@port70.net> X-Google-Sender-Auth: 7vdEJ_inhG5TPIyS0zWWbjdvw7s Original-Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Xref: news.gmane.org gmane.linux.kernel:2173346 gmane.linux.lib.musl.general:9539 Archived-At: On Wed, Mar 9, 2016 at 3:34 AM, Szabolcs Nagy wrote: >> >> Could someone remind me why cancellation points matter to user-space? > > because of standards. So quite frankly, if we have to do kernel support for this, then let's do it right, instead of just perpetuating a hack that was done in user space in a new way. We already have support for cancelling blocking system calls early: we do it for fatal signals (exactly because we know that it's ok to return -EINTR without failing POSIX semantics - the dying thread will never actually *see* the -EINTR because it's dying). I suspect that what you guys want is the same semantics as a fatal signal (return early with -EINTR), but without the actual fatality (you want to do cleanup in the cancelled thread). I suspect that we could fairly easily give those kinds of semantics. We could add a new flag to the sigaction (sa_flags) that says "this signal interrupts even uninterruptible system calls". Would that be good for you? And if not, can you explain the exact semantics you need? IThere might be some reason why you cannot reserve a particular signal for this, for example, but I'd like to know more precisely.. Because this "let's compare addresses" seems just excessively hacky. It's a clever little hack when you're doing user space and don't want to rely on kernel changes, but now that Andy is actuallty trying to push kernel changes it turns into just disgusting. Linus