linux-kernel - [PATCH 3/3] tracing/kprobes: unregister_trace

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Date:	Wed,  4 Aug 2010 18:26:04 -0300
From:	Arnaldo Carvalho de Melo <acme@...radead.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	linux-kernel@...r.kernel.org,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 3/3] tracing/kprobes: unregister_trace_probe needs to be called under mutex

From: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>

Comment in unregister_trace_probe() says probe_lock will be held when it
gets called. However there is a case where it might called without the
probe_lock being held. Also since we are traversing the probe_list and
deleting an element from the probe_list, probe_lock should be held.

This was first pointed in uprobes traceevent review by Frederic
Weisbecker here.  (http://lkml.org/lkml/2010/5/12/106)

Cc: Ingo Molnar <mingo@...e.hu>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Acked-by: Steven Rostedt <rostedt@...dmis.org>
LKML-Reference: <20100630084548.GA10325@...ux.vnet.ibm.com>
Signed-off-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 kernel/trace/trace_kprobe.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 1b79d1c..8b27c98 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -925,14 +925,17 @@ static int create_trace_probe(int argc, char **argv)
 			pr_info("Delete command needs an event name.\n");
 			return -EINVAL;
 		}
+		mutex_lock(&probe_lock);
 		tp = find_probe_event(event, group);
 		if (!tp) {
+			mutex_unlock(&probe_lock);
 			pr_info("Event %s/%s doesn't exist.\n", group, event);
 			return -ENOENT;
 		}
 		/* delete an event */
 		unregister_trace_probe(tp);
 		free_trace_probe(tp);
+		mutex_unlock(&probe_lock);
 		return 0;
 	}
 
-- 
1.6.2.5

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