From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752262AbZH0Roc (ORCPT ); Thu, 27 Aug 2009 13:44:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751742AbZH0Roa (ORCPT ); Thu, 27 Aug 2009 13:44:30 -0400 Received: from mail-ew0-f206.google.com ([209.85.219.206]:51769 "EHLO mail-ew0-f206.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751704AbZH0Rnn (ORCPT ); Thu, 27 Aug 2009 13:43:43 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:to:cc:subject:date:message-id:x-mailer:in-reply-to:references; b=O06hJzIKGBhbPFmKcfJ4X6WQibRZtaay+yaz07ZgZLFJdRu4cWoZX+vbgrwy+KykqQ +EM7Betd7EACAIg5+H12eDYdOJY13AjG04I2OLFtXHmrdrNK5shrN0TUd+N4AiA1No3j yOVqtB0lkdjjqIfZHP7Vt8nutZn+p80RqO5g4= From: Frederic Weisbecker To: Ingo Molnar Cc: LKML , Hendrik Brueckner , Jason Baron , Frederic Weisbecker , Ingo Molnar , Lai Jiangshan , Steven Rostedt , Peter Zijlstra , Mathieu Desnoyers , Jiaying Zhang , Martin Bligh , Li Zefan , Martin Schwidefsky , Paul Mundt , Heiko Carstens Subject: [PATCH 3/7] tracing: Don't trace kernel thread syscalls Date: Thu, 27 Aug 2009 19:43:31 +0200 Message-Id: <1251395015-6329-4-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 1.6.2.3 In-Reply-To: <1251395015-6329-1-git-send-email-fweisbec@gmail.com> References: <1251395015-6329-1-git-send-email-fweisbec@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Hendrik Brueckner Kernel threads don't call syscalls using the sysenter/sysexit path. Instead they directly call the sys_* or do_* functions that implement the syscalls inside the kernel. The current syscall tracepoints only bind the sysenter/sysexit path, then it has no effect to trace the kernel thread calls to syscalls in that path. Setting the TIF_SYSCALL_TRACEPOINT flag is then useless for these. Actually there is only one case when a kernel thread can reach the usual syscall exit tracing path: when we create a kernel thread, the child comes to ret_from_fork and is the fork() return is then traced. But this information alone is useless, then we don't want to set the TIF flags for these threads. Kernel threads have task_struct->mm set to NULL. (Thanks to Heiko for that hint ;-) The idea is then to check the mm field in syscall_regfunc() and set the flag accordingly. Signed-off-by: Hendrik Brueckner Cc: Jason Baron Cc: Frederic Weisbecker Cc: Ingo Molnar Cc: Lai Jiangshan Cc: Steven Rostedt Cc: Peter Zijlstra Cc: Mathieu Desnoyers Cc: Jiaying Zhang Cc: Martin Bligh Cc: Li Zefan Cc: Martin Schwidefsky Cc: Paul Mundt Cc: Heiko Carstens Cc: Hendrik Brueckner LKML-Reference: <20090825160237.GG4639@cetus.boeblingen.de.ibm.com> Signed-off-by: Frederic Weisbecker --- kernel/tracepoint.c | 4 +++- 1 files changed, 3 insertions(+), 1 deletions(-) diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c index 1a6a453..9489a0a 100644 --- a/kernel/tracepoint.c +++ b/kernel/tracepoint.c @@ -597,7 +597,9 @@ void syscall_regfunc(void) if (!sys_tracepoint_refcount) { read_lock_irqsave(&tasklist_lock, flags); do_each_thread(g, t) { - set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT); + /* Skip kernel threads. */ + if (t->mm) + set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT); } while_each_thread(g, t); read_unlock_irqrestore(&tasklist_lock, flags); } -- 1.6.2.3