On Thu, 02 Oct 2014 12:34:42 -0700
<gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> The patch below does not apply to the 3.16-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@xxxxxxxxxxxxxxx>.
>
Hah! I had a branch called ftrace-fixes-for-3.16-stable, which happened
to have this patch on it. Boy it feels good to plan ahead :-)
-- Steve
>From 554c4518d99f95a495fffd3fa67a5eece3109e5c Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (Red Hat)" <rostedt@xxxxxxxxxxx>
Date: Fri, 15 Aug 2014 17:18:46 -0400
Subject: [PATCH] ftrace: Fix function_profiler and function tracer together
The latest rewrite of ftrace removed the separate ftrace_ops of
the function tracer and the function graph tracer and had them
share the same ftrace_ops. This simplified the accounting by removing
the multiple layers of functions called. The global_ops func would
call a special list that would iterate over the other ops that
were registered within it (like function and function graph), which
itself was registered to the ftrace ops list of all functions
currently active.
The problem with this change was that it assumed that the function
and function graph tracer can never be used at the same time.
This is mostly true, but there is an exception. That is when the
function profiler uses the function graph tracer to profile.
The function profiler can be activated the same time as the function
tracer, and this breaks the assumption and the result is that ftrace
will crash (it detects the error and shuts itself down, it does not
cause a kernel oops).
To solve this issue, a previous change allowed the hash tables
for the functions traced by a ftrace_ops to be a pointer and let
multiple ftrace_ops share the same hash. This allows the function
and function_graph tracer to have separate ftrace_ops, but still
share the hash, which is what is done.
Now the function and function graph tracers have separate ftrace_ops
again, and the function tracer can be run while the function_profile
is active.
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
kernel/trace/ftrace.c | 49 ++++++++++++++++++++++++++++++++++++-------------
1 file changed, 36 insertions(+), 13 deletions(-)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 447e44230a23..bf512974dc57 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -68,8 +68,12 @@
#define INIT_OPS_HASH(opsname) \
.func_hash = &opsname.local_hash, \
.local_hash.regex_lock = __MUTEX_INITIALIZER(opsname.local_hash.regex_lock),
+#define ASSIGN_OPS_HASH(opsname, val) \
+ .func_hash = val, \
+ .local_hash.regex_lock = __MUTEX_INITIALIZER(opsname.local_hash.regex_lock),
#else
#define INIT_OPS_HASH(opsname)
+#define ASSIGN_OPS_HASH(opsname, val)
#endif
static struct ftrace_ops ftrace_list_end __read_mostly = {
@@ -110,6 +114,7 @@ static struct ftrace_ops *ftrace_ops_list __read_mostly = &ftrace_list_end;
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;
+static struct ftrace_ops graph_ops;
static struct ftrace_ops control_ops;
#if ARCH_SUPPORTS_FTRACE_OPS
@@ -4374,7 +4379,6 @@ void __init ftrace_init(void)
static struct ftrace_ops global_ops = {
.func = ftrace_stub,
.flags = FTRACE_OPS_FL_RECURSION_SAFE | FTRACE_OPS_FL_INITIALIZED,
- INIT_OPS_HASH(global_ops)
};
static int __init ftrace_nodyn_init(void)
@@ -4912,6 +4916,14 @@ ftrace_enable_sysctl(struct ctl_table *table, int write,
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+static struct ftrace_ops graph_ops = {
+ .func = ftrace_stub,
+ .flags = FTRACE_OPS_FL_RECURSION_SAFE |
+ FTRACE_OPS_FL_INITIALIZED |
+ FTRACE_OPS_FL_STUB,
+ ASSIGN_OPS_HASH(graph_ops, &global_ops.local_hash)
+};
+
static int ftrace_graph_active;
int ftrace_graph_entry_stub(struct ftrace_graph_ent *trace)
@@ -5074,12 +5086,28 @@ static int ftrace_graph_entry_test(struct ftrace_graph_ent *trace)
*/
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
+ struct ftrace_ops *op;
+ bool do_test = false;
+
+ /*
+ * The graph and global ops share the same set of functions
+ * to test. If any other ops is on the list, then
+ * the graph tracing needs to test if its the function
+ * it should call.
+ */
+ do_for_each_ftrace_op(op, ftrace_ops_list) {
+ if (op != &global_ops && op != &graph_ops &&
+ op != &ftrace_list_end) {
+ do_test = true;
+ /* in double loop, break out with goto */
+ goto out;
+ }
+ } while_for_each_ftrace_op(op);
+ out:
+ if (do_test)
ftrace_graph_entry = ftrace_graph_entry_test;
+ else
+ ftrace_graph_entry = __ftrace_graph_entry;
}
static struct notifier_block ftrace_suspend_notifier = {
@@ -5120,11 +5148,7 @@ int register_ftrace_graph(trace_func_graph_ret_t retfunc,
ftrace_graph_entry = ftrace_graph_entry_test;
update_function_graph_func();
- /* Function graph doesn't use the .func field of global_ops */
- global_ops.flags |= FTRACE_OPS_FL_STUB;
-
- ret = ftrace_startup(&global_ops, FTRACE_START_FUNC_RET);
-
+ ret = ftrace_startup(&graph_ops, FTRACE_START_FUNC_RET);
out:
mutex_unlock(&ftrace_lock);
return ret;
@@ -5141,8 +5165,7 @@ void unregister_ftrace_graph(void)
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(&global_ops, FTRACE_STOP_FUNC_RET);
- global_ops.flags &= ~FTRACE_OPS_FL_STUB;
+ ftrace_shutdown(&graph_ops, FTRACE_STOP_FUNC_RET);
unregister_pm_notifier(&ftrace_suspend_notifier);
unregister_trace_sched_switch(ftrace_graph_probe_sched_switch, NULL);
--
1.8.1.4
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