Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757512AbZCQQFs (ORCPT ); Tue, 17 Mar 2009 12:05:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754920AbZCQQFi (ORCPT ); Tue, 17 Mar 2009 12:05:38 -0400 Received: from tomts40.bellnexxia.net ([209.226.175.97]:36210 "EHLO tomts40-srv.bellnexxia.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752304AbZCQQFi (ORCPT ); Tue, 17 Mar 2009 12:05:38 -0400 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: As0FALNkv0lMQW1W/2dsb2JhbACBTtNug3wG Date: Tue, 17 Mar 2009 12:00:29 -0400 From: Mathieu Desnoyers To: Oleg Nesterov Cc: Lai Jiangshan , Peter Zijlstra , Frederic Weisbecker , linux-kernel@vger.kernel.org, Steven Rostedt , Jiaying Zhang , Martin Bligh , utrace-devel@redhat.com Subject: Re: [RFC][PATCH 1/2] tracing/ftrace: syscall tracing infrastructure Message-ID: <20090317160029.GD10092@Krystal> References: <1236401580-5758-1-git-send-email-fweisbec@gmail.com> <1236401580-5758-2-git-send-email-fweisbec@gmail.com> <49BEAA5A.4030708@redhat.com> <20090316201526.GE8393@nowhere> <49BEB8C4.2010606@redhat.com> <20090316214526.GA15119@Krystal> <20090317052442.GA32674@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: <20090317052442.GA32674@redhat.com> X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.21.3-grsec (i686) X-Uptime: 11:45:31 up 17 days, 12:11, 1 user, load average: 0.51, 0.80, 0.61 User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1621 Lines: 46 * Oleg Nesterov (oleg@redhat.com) wrote: > On 03/16, Mathieu Desnoyers wrote: > > > > utrace_add_engine() > > set_notify_resume(target); > > > > ok, so this is where the TIF_NOTIFY_RESUME thread flag is set. I notice > > that it is set asynchronously with the execution of the target thread > > (as I do with my TIF_KERNEL_TRACE thread flag). > > > > However, on x86_64, _TIF_DO_NOTIFY_MASK is only tested in > > entry_64.S > > > > int_signal: > > and > > retint_signal: > > > > code paths. However, if there is no syscall tracing to do upon syscall > > entry, the thread flags are not re-read at syscall exit and you will > > miss the syscall exit returning from your target thread if this thread > > was blocked while you set its TIF_NOTIFY_RESUME. > > Afaics, TIF_NOTIFY_RESUME is not needed to trace syscall entry/exit. > If engine wants the syscall tracing, utrace_set_events(UTRACE_SYSCALL_xxx) > sets TIF_SYSCALL_TRACE. And syscall_trace_enter/syscall_trace_leave call > tracehook_report_syscall_xxx(). > > Oleg. I recall that TIF_SYSCALL_TRACE also suffers from the same problem as TIF_NOTIFY_RESUME if set asynchronously with the target thread's execution at least on x86_64 and arm. Do you take care to stop the target thread in utrace_set_events ? Mathieu > -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 -- 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/