From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sat, 2 Feb 2002 11:07:42 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sat, 2 Feb 2002 11:07:32 -0500 Received: from smtpzilla1.xs4all.nl ([194.109.127.137]:49669 "EHLO smtpzilla1.xs4all.nl") by vger.kernel.org with ESMTP id ; Sat, 2 Feb 2002 11:07:18 -0500 Message-ID: <3C5C0EAE.6266F70A@linux-m68k.org> Date: Sat, 02 Feb 2002 17:07:10 +0100 From: Roman Zippel X-Mailer: Mozilla 4.77 [en] (X11; U; Linux 2.4.17 i686) X-Accept-Language: en MIME-Version: 1.0 To: David Howells CC: torvalds@transmeta.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] syscall latency improvement #1 (253p6) In-Reply-To: <9849.1012317950@warthog.cambridge.redhat.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi, David Howells wrote: > +/* this struct must occupy one 32-bit chunk so that is can be read in one go */ > +struct task_work { > + __s8 need_resched; > + __u8 syscall_trace; /* count of syscall interceptors */ > + __u8 sigpending; > + __u8 notify_resume; /* request for notification on > + userspace execution resumption */ > +} __attribute__((packed)); > + Did you test whether single stepping over a single syscall works? From reading the patch/source I can't see how it should, but I haven't tested it yet. The problem is that syscall tracing is only important at syscall entry. At syscall exit we have to check whether single stepping is active. These are two different operations, but I only see two tests against syscall_trace. BTW it doesn't work with 2.4, but there is no test for PT_DTRACE at all, so it's not really surprising. Second, could we move above structure into e.g. ? This would allow architectures to reorder the bytes, as above is obviously optimized for little endian machines. bye, Roman