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authorSteven Rostedt <srostedt@redhat.com>2011-07-13 15:11:02 -0400
committerSteven Rostedt <rostedt@goodmis.org>2011-07-13 22:25:09 -0400
commit6331c28c962561aee59e5a493b7556a4bb585957 (patch)
tree33292a3127aa831ee8ec2394e790bc2a8817beee /kernel/trace/ftrace.c
parent072126f4529196f71a97960248bca54fd4554c2d (diff)
ftrace: Fix dynamic selftest failure on some archs
Archs that do not implement CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST, will fail the dynamic ftrace selftest. The function tracer has a quick 'off' variable that will prevent the call back functions from being called. This variable is called function_trace_stop. In x86, this is implemented directly in the mcount assembly, but for other archs, an intermediate function is used called ftrace_test_stop_func(). In dynamic ftrace, the function pointer variable ftrace_trace_function is used to update the caller code in the mcount caller. But for archs that do not have CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST set, it only calls ftrace_test_stop_func() instead, which in turn calls __ftrace_trace_function. When more than one ftrace_ops is registered, the function it calls is ftrace_ops_list_func(), which will iterate over all registered ftrace_ops and call the callbacks that have their hash matching. The issue happens when two ftrace_ops are registered for different functions and one is then unregistered. The __ftrace_trace_function is then pointed to the remaining ftrace_ops callback function directly. This mean it will be called for all functions that were registered to trace by both ftrace_ops that were registered. This is not an issue for archs with CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST, because the update of ftrace_trace_function doesn't happen until after all functions have been updated, and then the mcount caller is updated. But for those archs that do use the ftrace_test_stop_func(), the update is immediate. The dynamic selftest fails because it hits this situation, and the ftrace_ops that it registers fails to only trace what it was suppose to and instead traces all other functions. The solution is to delay the setting of __ftrace_trace_function until after all the functions have been updated according to the registered ftrace_ops. Also, function_trace_stop is set during the update to prevent function tracing from calling code that is caused by the function tracer itself. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace/ftrace.c')
-rw-r--r--kernel/trace/ftrace.c26
1 files changed, 26 insertions, 0 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index a0dc0de8d64..62e26d93053 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -88,6 +88,7 @@ static struct ftrace_ops ftrace_list_end __read_mostly = {
static struct ftrace_ops *ftrace_global_list __read_mostly = &ftrace_list_end;
static struct ftrace_ops *ftrace_ops_list __read_mostly = &ftrace_list_end;
ftrace_func_t ftrace_trace_function __read_mostly = ftrace_stub;
+static ftrace_func_t __ftrace_trace_function_delay __read_mostly = ftrace_stub;
ftrace_func_t __ftrace_trace_function __read_mostly = ftrace_stub;
ftrace_func_t ftrace_pid_function __read_mostly = ftrace_stub;
static struct ftrace_ops global_ops;
@@ -146,9 +147,11 @@ void clear_ftrace_function(void)
{
ftrace_trace_function = ftrace_stub;
__ftrace_trace_function = ftrace_stub;
+ __ftrace_trace_function_delay = ftrace_stub;
ftrace_pid_function = ftrace_stub;
}
+#undef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
#ifndef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
/*
* For those archs that do not test ftrace_trace_stop in their
@@ -208,7 +211,12 @@ static void update_ftrace_function(void)
#ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
ftrace_trace_function = func;
#else
+#ifdef CONFIG_DYNAMIC_FTRACE
+ /* do not update till all functions have been modified */
+ __ftrace_trace_function_delay = func;
+#else
__ftrace_trace_function = func;
+#endif
ftrace_trace_function = ftrace_test_stop_func;
#endif
}
@@ -1607,6 +1615,12 @@ static int __ftrace_modify_code(void *data)
{
int *command = data;
+ /*
+ * Do not call function tracer while we update the code.
+ * We are in stop machine, no worrying about races.
+ */
+ function_trace_stop++;
+
if (*command & FTRACE_ENABLE_CALLS)
ftrace_replace_code(1);
else if (*command & FTRACE_DISABLE_CALLS)
@@ -1620,6 +1634,18 @@ static int __ftrace_modify_code(void *data)
else if (*command & FTRACE_STOP_FUNC_RET)
ftrace_disable_ftrace_graph_caller();
+#ifndef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
+ /*
+ * For archs that call ftrace_test_stop_func(), we must
+ * wait till after we update all the function callers
+ * before we update the callback. This keeps different
+ * ops that record different functions from corrupting
+ * each other.
+ */
+ __ftrace_trace_function = __ftrace_trace_function_delay;
+#endif
+ function_trace_stop--;
+
return 0;
}