[PATCH] tracing: Fix infinite loop in ftrace_update_pid_func()

Matt Fleming
2009-09-28T15:42:28Z

From: Matt Fleming <matthew.fleming@imgtec.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@imgtec.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