From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754595AbZCFG3x (ORCPT ); Fri, 6 Mar 2009 01:29:53 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752544AbZCFG3P (ORCPT ); Fri, 6 Mar 2009 01:29:15 -0500 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:58639 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752252AbZCFG3N (ORCPT ); Fri, 6 Mar 2009 01:29:13 -0500 From: KOSAKI Motohiro To: LKML , Steven Rostedt , Ingo Molnar Subject: [PATCH for tip][bugfix] ftrace: fix deadlock when setting set_ftrace_pid Cc: kosaki.motohiro@jp.fujitsu.com Message-Id: <20090306151155.0778.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Becky! ver. 2.50 [ja] Date: Fri, 6 Mar 2009 15:29:04 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Impact: fix deadlock bug reproduce way: # cd /sys/kernel/debug/tracing # echo $$ > set_ftrace_pid then, console become hangup. detail: when writing set_ftracepid, kernel callstack is following ftrace_pid_write() mutex_lock(&ftrace_lock); ftrace_update_pid_func() mutex_lock(&ftrace_lock); mutex_unlock(&ftrace_lock); mutex_unlock(&ftrace_lock); then, system alaways deadlock when ftrace_pid_write() is called. In past days, ftrace_pid_write() use ftrace_start_lock, but commit e6ea44e9b4c12325337cd1c06103cd515a1c02b2 consolidate ftrace_start_lock to ftrace_lock. Signed-off-by: KOSAKI Motohiro --- diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 5a3a06b..0d3b393 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -218,10 +218,8 @@ static void ftrace_update_pid_func(void) { ftrace_func_t func; - mutex_lock(&ftrace_lock); - if (ftrace_trace_function == ftrace_stub) - goto out; + return; func = ftrace_trace_function; @@ -238,9 +236,6 @@ static void ftrace_update_pid_func(void) #else __ftrace_trace_function = func; #endif - - out: - mutex_unlock(&ftrace_lock); } /* set when tracing only a pid */