From: Steven Rostedt <srostedt@redhat.com>
Date: Tue, 24 Mar 2009 04:18:31 +0000 (-0400)
Subject: function-graph: prevent more than one tracer registering
X-Git-Tag: v2.6.31-rc1~401^2~205
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=05ce5818adee8f8efd0a5ca0d900a6789012516b;p=profile%2Fivi%2Fkernel-x86-ivi.git

function-graph: prevent more than one tracer registering

Impact: prevent crash due to multiple function graph tracers

The function graph tracer can currently only handle a single tracer
being registered. If another tracer registers with the function
graph tracer it can crash the system.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 7847806..c81a759 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2643,6 +2643,12 @@ int register_ftrace_graph(trace_func_graph_ret_t retfunc,
 
 	mutex_lock(&ftrace_lock);
 
+	/* we currently allow only one tracer registered at a time */
+	if (atomic_read(&ftrace_graph_active)) {
+		ret = -EBUSY;
+		goto out;
+	}
+
 	ftrace_suspend_notifier.notifier_call = ftrace_suspend_notifier_call;
 	register_pm_notifier(&ftrace_suspend_notifier);