linux-kernel - Re: [PATCH 02/10] perf, trace: Use per-tracepoint-per-cpu hlist to track events

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Date:	Fri, 21 May 2010 16:25:13 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	rostedt@...dmis.org
Cc:	Ingo Molnar <mingo@...e.hu>, Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 02/10] perf, trace: Use per-tracepoint-per-cpu hlist to
 track events

On Fri, 2010-05-21 at 16:18 +0200, Peter Zijlstra wrote:
> 
> > That tp_event->perf_refcount is global to the event not to the perf
> > event.
> 
> Oh, bugger, yes. I seem to have lost it on destroy..


---
Subject: perf, trace: Fix perf_trace_destroy(), mutex went missing
From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Date: Fri May 21 16:22:33 CEST 2010

Steve spotted I forgot to do the destroy under event_mutex.

Reported-by: Steven Rostedt <rostedt@...dmis.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
LKML-Reference: <new-submission>
---
 kernel/trace/trace_event_perf.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

Index: linux-2.6/kernel/trace/trace_event_perf.c
===================================================================
--- linux-2.6.orig/kernel/trace/trace_event_perf.c
+++ linux-2.6/kernel/trace/trace_event_perf.c
@@ -125,8 +125,9 @@ void perf_trace_destroy(struct perf_even
 	struct ftrace_event_call *tp_event = p_event->tp_event;
 	int i;
 
+	mutex_lock(&event_mutex);
 	if (--tp_event->perf_refcount > 0)
-		return;
+		goto out;
 
 	tp_event->perf_event_disable(tp_event);
 
@@ -145,6 +146,8 @@ void perf_trace_destroy(struct perf_even
 			perf_trace_buf[i] = NULL;
 		}
 	}
+out:
+	mutex_unlock(&event_mutex);
 }
 
 __kprobes void *perf_trace_buf_prepare(int size, unsigned short type,


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