Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S265214AbUF2Dmq (ORCPT ); Mon, 28 Jun 2004 23:42:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S265353AbUF2Dmq (ORCPT ); Mon, 28 Jun 2004 23:42:46 -0400 Received: from fw.osdl.org ([65.172.181.6]:25017 "EHLO mail.osdl.org") by vger.kernel.org with ESMTP id S265214AbUF2Dmp (ORCPT ); Mon, 28 Jun 2004 23:42:45 -0400 Date: Mon, 28 Jun 2004 20:42:35 -0700 (PDT) From: Linus Torvalds To: Roland McGrath cc: Andrew Morton , Ingo Molnar , Andrew Cagney , Linux Kernel Mailing List Subject: Re: [RFC PATCH] x86 single-step (TF) vs system calls & traps In-Reply-To: <200406290155.i5T1tKYY030209@magilla.sf.frob.com> Message-ID: References: <200406290155.i5T1tKYY030209@magilla.sf.frob.com> 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: 796 Lines: 20 On Mon, 28 Jun 2004, Roland McGrath wrote: > > When you single-step into a trap instruction, you actually don't get a > SIGTRAP until the instruction after the trap instruction has also executed. Yes. This is documented Intel behaviour. It also guarantees that there is forward progress in some strange circumstances, if I remember correctly. And I refuse to make the fast-path slower just because of this. Not only has Linux always worked like this, as far as I know all other x86 OS's also tend to just do the Intel behaviour thing. Linus - 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/