linux-kernel - [PATCH] tracing: Fix infinite loop in ftrace_update_pid

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Message-Id: <1254152581-18347-1-git-send-email-matt@console-pimps.org>
Date:	Mon, 28 Sep 2009 16:43:01 +0100
From:	Matt Fleming <matt@...sole-pimps.org>
To:	linux-kernel@...r.kernel.org
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>
Subject: [PATCH] tracing: Fix infinite loop in ftrace_update_pid_func()

From: Matt Fleming <matthew.fleming@...tec.com>

When CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST is enabled
__ftrace_trace_function contains the current trace function, not
ftrace_trace_function. In ftrace_update_pid_func() we currently
incorrectly assign the value of ftrace_trace_function to
__ftrace_trace_funcion before returning.

Without this patch it is possible to execute an infinite loop whereby
ftrace_test_stop_func() calls __ftrace_trace_function, which was
assigned ftrace_test_stop_func() in ftrace_update_pid_func().

Signed-off-by: Matt Fleming <matthew.fleming@...tec.com>
---
 kernel/trace/ftrace.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 25edd5c..d9ba6d9 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -225,7 +225,11 @@ static void ftrace_update_pid_func(void)
 	if (ftrace_trace_function == ftrace_stub)
 		return;
 
+#ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
 	func = ftrace_trace_function;
+#else
+	func = __ftrace_trace_function;
+#endif
 
 	if (ftrace_pid_trace) {
 		set_ftrace_pid_function(func);
-- 
1.6.3.GIT

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