From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756891Ab3HaFRP (ORCPT ); Sat, 31 Aug 2013 01:17:15 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:32184 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755809Ab3HaFRG (ORCPT ); Sat, 31 Aug 2013 01:17:06 -0400 X-Authority-Analysis: v=2.0 cv=ddwCLAre c=1 sm=0 a=Sro2XwOs0tJUSHxCKfOySw==:17 a=Drc5e87SC40A:10 a=Ciwy3NGCPMMA:10 a=9S8HIjYI5LQA:10 a=5SG0PmZfjMsA:10 a=bbbx4UPp9XUA:10 a=meVymXHHAAAA:8 a=KGjhK52YXX0A:10 a=NQVHccLqZjsA:10 a=jREKiASAg2tDcGA6ehgA:9 a=jeBq3FmKZ4MA:10 a=Sro2XwOs0tJUSHxCKfOySw==:117 X-Cloudmark-Score: 0 X-Authenticated-User: X-Originating-IP: 67.255.60.225 Message-Id: <20130831051702.436132384@goodmis.org> User-Agent: quilt/0.60-1 Date: Sat, 31 Aug 2013 01:11:29 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , Peter Zijlstra , Frederic Weisbecker , "Paul E. McKenney" , Jiri Olsa Subject: [RFC][PATCH 12/18 v2] ftrace: Disable RCU unsafe checker when function graph is enabled References: <20130831051117.884125230@goodmis.org> Content-Disposition: inline; filename=0012-ftrace-Disable-RCU-unsafe-checker-when-function-grap.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Steven Rostedt (Red Hat)" Having the RCU unsafe checker running when function graph is enabled can cause a live lock. That's because the RCU unsafe checker enables full lockdep debugging on RCU which does a lot of interal calls that may be traced by the function graph tacer. This adds quite a bit of overhead and can possibly live lock the system. Just do not do the RCU unsafe checks when function graph tracer is enabled. Signed-off-by: Steven Rostedt --- kernel/trace/ftrace.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 69b7f62..310b727 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -5118,6 +5118,12 @@ int register_ftrace_graph(trace_func_graph_ret_t retfunc, goto out; } + /* + * The Unsafe RCU checker can live lock function graph tracing. + * It's best to just disable it while doing the fgraph tracing. + */ + ftrace_unsafe_rcu_checker_disable(); + ftrace_graph_return = retfunc; ftrace_graph_entry = entryfunc; @@ -5141,6 +5147,7 @@ void unregister_ftrace_graph(void) ftrace_shutdown(&global_ops, FTRACE_STOP_FUNC_RET); unregister_pm_notifier(&ftrace_suspend_notifier); unregister_trace_sched_switch(ftrace_graph_probe_sched_switch, NULL); + ftrace_unsafe_rcu_checker_enable(); out: mutex_unlock(&ftrace_lock); -- 1.7.10.4