linux-kernel - Re: regression 3.11-rc1: rmmod hangs after tracing module

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Date:	Tue, 23 Jul 2013 14:44:37 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Arend van Spriel <arend@...adcom.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Subject: Re: regression 3.11-rc1: rmmod hangs after tracing module

On Tue, 2013-07-23 at 20:07 +0200, Arend van Spriel wrote:
> Hi Steven,
> 
> During testing of our brcmfmac wireless driver I had a trace-cmd running 
> along (trace-cmd record -e brcmfmac:*). After the test I stopped the 
> trace, unplugged my usb device and did a rmmod resulting in the attached 
> lockdep splat. Hope you have an idea what is going wrong here.

Thanks for the report!

Does this fix you bug?

-- Steve

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 69cba47..882ec1d 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1224,18 +1224,17 @@ void tracing_reset_current(int cpu)
 	tracing_reset(&global_trace.trace_buffer, cpu);
 }
 
+/* Must have trace_types_lock held */
 void tracing_reset_all_online_cpus(void)
 {
 	struct trace_array *tr;
 
-	mutex_lock(&trace_types_lock);
 	list_for_each_entry(tr, &ftrace_trace_arrays, list) {
 		tracing_reset_online_cpus(&tr->trace_buffer);
 #ifdef CONFIG_TRACER_MAX_TRACE
 		tracing_reset_online_cpus(&tr->max_buffer);
 #endif
 	}
-	mutex_unlock(&trace_types_lock);
 }
 
 #define SAVED_CMDLINES 128


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