+++ /dev/null
-From 23a8e8441a0a74dd612edf81dc89d1600bc0a3d1 Mon Sep 17 00:00:00 2001
-From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>
-Date: Mon, 13 Jan 2014 10:30:23 -0500
-Subject: ftrace: Have function graph only trace based on global_ops filters
-
-From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>
-
-commit 23a8e8441a0a74dd612edf81dc89d1600bc0a3d1 upstream.
-
-Doing some different tests, I discovered that function graph tracing, when
-filtered via the set_ftrace_filter and set_ftrace_notrace files, does
-not always keep with them if another function ftrace_ops is registered
-to trace functions.
-
-The reason is that function graph just happens to trace all functions
-that the function tracer enables. When there was only one user of
-function tracing, the function graph tracer did not need to worry about
-being called by functions that it did not want to trace. But now that there
-are other users, this becomes a problem.
-
-For example, one just needs to do the following:
-
- # cd /sys/kernel/debug/tracing
- # echo schedule > set_ftrace_filter
- # echo function_graph > current_tracer
- # cat trace
-[..]
- 0) | schedule() {
- ------------------------------------------
- 0) <idle>-0 => rcu_pre-7
- ------------------------------------------
-
- 0) ! 2980.314 us | }
- 0) | schedule() {
- ------------------------------------------
- 0) rcu_pre-7 => <idle>-0
- ------------------------------------------
-
- 0) + 20.701 us | }
-
- # echo 1 > /proc/sys/kernel/stack_tracer_enabled
- # cat trace
-[..]
- 1) + 20.825 us | }
- 1) + 21.651 us | }
- 1) + 30.924 us | } /* SyS_ioctl */
- 1) | do_page_fault() {
- 1) | __do_page_fault() {
- 1) 0.274 us | down_read_trylock();
- 1) 0.098 us | find_vma();
- 1) | handle_mm_fault() {
- 1) | _raw_spin_lock() {
- 1) 0.102 us | preempt_count_add();
- 1) 0.097 us | do_raw_spin_lock();
- 1) 2.173 us | }
- 1) | do_wp_page() {
- 1) 0.079 us | vm_normal_page();
- 1) 0.086 us | reuse_swap_page();
- 1) 0.076 us | page_move_anon_rmap();
- 1) | unlock_page() {
- 1) 0.082 us | page_waitqueue();
- 1) 0.086 us | __wake_up_bit();
- 1) 1.801 us | }
- 1) 0.075 us | ptep_set_access_flags();
- 1) | _raw_spin_unlock() {
- 1) 0.098 us | do_raw_spin_unlock();
- 1) 0.105 us | preempt_count_sub();
- 1) 1.884 us | }
- 1) 9.149 us | }
- 1) + 13.083 us | }
- 1) 0.146 us | up_read();
-
-When the stack tracer was enabled, it enabled all functions to be traced, which
-now the function graph tracer also traces. This is a side effect that should
-not occur.
-
-To fix this a test is added when the function tracing is changed, as well as when
-the graph tracer is enabled, to see if anything other than the ftrace global_ops
-function tracer is enabled. If so, then the graph tracer calls a test trampoline
-that will look at the function that is being traced and compare it with the
-filters defined by the global_ops.
-
-As an optimization, if there's no other function tracers registered, or if
-the only registered function tracers also use the global ops, the function
-graph infrastructure will call the registered function graph callback directly
-and not go through the test trampoline.
-
-Fixes: d2d45c7a03a2 "tracing: Have stack_tracer use a separate list of functions"
-Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
-Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-
----
- kernel/trace/ftrace.c | 45 ++++++++++++++++++++++++++++++++++++++++++++-
- 1 file changed, 44 insertions(+), 1 deletion(-)
-
---- a/kernel/trace/ftrace.c
-+++ b/kernel/trace/ftrace.c
-@@ -222,6 +222,12 @@ static void update_global_ops(void)
- global_ops.func = func;
- }
-
-+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
-+static void update_function_graph_func(void);
-+#else
-+static inline void update_function_graph_func(void) { }
-+#endif
-+
- static void update_ftrace_function(void)
- {
- ftrace_func_t func;
-@@ -270,6 +276,8 @@ static int remove_ftrace_ops(struct ftra
- {
- struct ftrace_ops **p;
-
-+ update_function_graph_func();
-+
- /*
- * If we are removing the last function, then simply point
- * to the ftrace_stub.
-@@ -4404,6 +4412,7 @@ int ftrace_graph_entry_stub(struct ftrac
- trace_func_graph_ret_t ftrace_graph_return =
- (trace_func_graph_ret_t)ftrace_stub;
- trace_func_graph_ent_t ftrace_graph_entry = ftrace_graph_entry_stub;
-+static trace_func_graph_ent_t __ftrace_graph_entry = ftrace_graph_entry_stub;
-
- /* Try to assign a return stack array on FTRACE_RETSTACK_ALLOC_SIZE tasks. */
- static int alloc_retstack_tasklist(struct ftrace_ret_stack **ret_stack_list)
-@@ -4544,6 +4553,30 @@ static struct ftrace_ops fgraph_ops __re
- .flags = FTRACE_OPS_FL_GLOBAL,
- };
-
-+static int ftrace_graph_entry_test(struct ftrace_graph_ent *trace)
-+{
-+ if (!ftrace_ops_test(&global_ops, trace->func, NULL))
-+ return 0;
-+ return __ftrace_graph_entry(trace);
-+}
-+
-+/*
-+ * The function graph tracer should only trace the functions defined
-+ * by set_ftrace_filter and set_ftrace_notrace. If another function
-+ * tracer ops is registered, the graph tracer requires testing the
-+ * function against the global ops, and not just trace any function
-+ * that any ftrace_ops registered.
-+ */
-+static void update_function_graph_func(void)
-+{
-+ if (ftrace_ops_list == &ftrace_list_end ||
-+ (ftrace_ops_list == &global_ops &&
-+ global_ops.next == &ftrace_list_end))
-+ ftrace_graph_entry = __ftrace_graph_entry;
-+ else
-+ ftrace_graph_entry = ftrace_graph_entry_test;
-+}
-+
- int register_ftrace_graph(trace_func_graph_ret_t retfunc,
- trace_func_graph_ent_t entryfunc)
- {
-@@ -4568,7 +4601,16 @@ int register_ftrace_graph(trace_func_gra
- }
-
- ftrace_graph_return = retfunc;
-- ftrace_graph_entry = entryfunc;
-+
-+ /*
-+ * Update the indirect function to the entryfunc, and the
-+ * function that gets called to the entry_test first. Then
-+ * call the update fgraph entry function to determine if
-+ * the entryfunc should be called directly or not.
-+ */
-+ __ftrace_graph_entry = entryfunc;
-+ ftrace_graph_entry = ftrace_graph_entry_test;
-+ update_function_graph_func();
-
- ret = ftrace_startup(&fgraph_ops, FTRACE_START_FUNC_RET);
-
-@@ -4587,6 +4629,7 @@ void unregister_ftrace_graph(void)
- ftrace_graph_active--;
- ftrace_graph_return = (trace_func_graph_ret_t)ftrace_stub;
- ftrace_graph_entry = ftrace_graph_entry_stub;
-+ __ftrace_graph_entry = ftrace_graph_entry_stub;
- ftrace_shutdown(&fgraph_ops, FTRACE_STOP_FUNC_RET);
- unregister_pm_notifier(&ftrace_suspend_notifier);
- unregister_trace_sched_switch(ftrace_graph_probe_sched_switch, NULL);
projects / thirdparty / kernel / stable-queue.git / commitdiff
