Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933454AbXBEVJV (ORCPT ); Mon, 5 Feb 2007 16:09:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933452AbXBEVJV (ORCPT ); Mon, 5 Feb 2007 16:09:21 -0500 Received: from x35.xmailserver.org ([64.71.152.41]:4103 "EHLO x35.xmailserver.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933454AbXBEVJU (ORCPT ); Mon, 5 Feb 2007 16:09:20 -0500 X-AuthUser: davidel@xmailserver.org Date: Mon, 5 Feb 2007 13:09:17 -0800 (PST) From: Davide Libenzi X-X-Sender: davide@alien.or.mcafeemobile.com To: Linus Torvalds cc: Zach Brown , Ingo Molnar , Linux Kernel Mailing List , linux-aio@kvack.org, Suparna Bhattacharya , Benjamin LaHaise Subject: Re: [PATCH 2 of 4] Introduce i386 fibril scheduling In-Reply-To: Message-ID: References: <20070201083611.GC18233@elte.hu> <20070202104900.GA13941@elte.hu> <20070202222110.GA1212@elte.hu> <20070202235531.GA18904@elte.hu> <20070203082308.GA6748@elte.hu> <8CF4BE18-8EEF-4ACA-A4B4-B627ED3B4831@oracle.com> 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 Content-Length: 1909 Lines: 48 On Mon, 5 Feb 2007, Linus Torvalds wrote: > Indeed. One word is *exactly* what a normal system call returns too. > > That said, normally we have a user-space library layer to turn that into > the "errno + return value" thing, and in the case of async() calls we > very basically wouldn't have that. So either: > > - we'd need to do it in the kernel (which is actually nasty, since > different system calls have slightly different semantics - some don't > return any error value at all, and negative numbers are real numbers) > > - we'd have to teach user space about the "negative errno" mechanism, in > which case one word really is alwats enough. > > Quite frankly, I much prefer the second alternative. The "negative errno" > thing has not only worked really really well inside the kernel, it's so > obviously 100% superior to the standard UNIX "-1 + errno" approach that > it's not even funny. Currently it's in the syscall wrapper. Couldn't we have it in the asys_teardown_stack() stub? > HOWEVER, they get returned differently. The cookie gets returned > immediately, the system call result gets returned in-memory only after the > async thing has actually completed. > > I would actually argue that it's not the kernel that should generate any > cookie, but that user-space should *pass*in* the cookie it wants to, and > the kernel should consider it a pointer to a 64-bit entity which is the > return code. Yes. Let's have the userspace to "mark" the async operation. IMO the cookie should be something transparent to the kernel. Like you said though, that'd require compat-code (unless we fix the size). - Davide - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/