From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754649AbZCFLKO (ORCPT ); Fri, 6 Mar 2009 06:10:14 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751573AbZCFLJ7 (ORCPT ); Fri, 6 Mar 2009 06:09:59 -0500 Received: from hera.kernel.org ([140.211.167.34]:36521 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751406AbZCFLJ6 (ORCPT ); Fri, 6 Mar 2009 06:09:58 -0500 Date: Fri, 6 Mar 2009 11:09:23 GMT From: KOSAKI Motohiro To: linux-tip-commits@vger.kernel.org Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, srostedt@redhat.com, tglx@linutronix.de, laijs@cn.fujitsu.com, kosaki.motohiro@jp.fujitsu.com, mingo@elte.hu Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, srostedt@redhat.com, tglx@linutronix.de, kosaki.motohiro@jp.fujitsu.com, laijs@cn.fujitsu.com, mingo@elte.hu In-Reply-To: <20090306151155.0778.A69D9226@jp.fujitsu.com> References: <20090306151155.0778.A69D9226@jp.fujitsu.com> Subject: [tip:tracing/ftrace] tracing: fix deadlock when setting set_ftrace_pid Message-ID: Git-Commit-ID: 10dd3ebe213c31bff14b4dae3c5d32a76b1fad7c X-Mailer: tip-git-log-daemon MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.0 (hera.kernel.org [127.0.0.1]); Fri, 06 Mar 2009 11:09:25 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 10dd3ebe213c31bff14b4dae3c5d32a76b1fad7c Gitweb: http://git.kernel.org/tip/10dd3ebe213c31bff14b4dae3c5d32a76b1fad7c Author: "KOSAKI Motohiro" AuthorDate: Fri, 6 Mar 2009 15:29:04 +0900 Commit: Ingo Molnar CommitDate: Fri, 6 Mar 2009 12:07:38 +0100 tracing: fix deadlock when setting set_ftrace_pid Impact: fix deadlock while using set_ftrace_pid Reproducer: # cd /sys/kernel/debug/tracing # echo $$ > set_ftrace_pid then, console becomes hung. Details: 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 always deadlocks when ftrace_pid_write() is called. In past days, ftrace_pid_write() used ftrace_start_lock, but commit e6ea44e9b4c12325337cd1c06103cd515a1c02b2 consolidated ftrace_start_lock to ftrace_lock. Signed-off-by: KOSAKI Motohiro Reviewed-by: Lai Jiangshan Cc: Steven Rostedt LKML-Reference: <20090306151155.0778.A69D9226@jp.fujitsu.com> Signed-off-by: Ingo Molnar --- kernel/trace/ftrace.c | 7 +------ 1 files changed, 1 insertions(+), 6 deletions(-) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index d7a06a0..d33d306 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 */