tracing: Add 'stacktrace' event trigger command

Add 'stacktrace' event_command.  stacktrace event triggers are added
by the user via this command in a similar way and using practically
the same syntax as the analogous 'stacktrace' ftrace function command,
but instead of writing to the set_ftrace_filter file, the stacktrace
event trigger is written to the per-event 'trigger' files:

    echo 'stacktrace' > .../tracing/events/somesys/someevent/trigger

The above command will turn on stacktraces for someevent i.e. whenever
someevent is hit, a stacktrace will be logged.

This also adds a 'count' version that limits the number of times the
command will be invoked:

    echo 'stacktrace:N' > .../tracing/events/somesys/someevent/trigger

Where N is the number of times the command will be invoked.

The above command will log N stacktraces for someevent i.e. whenever
someevent is hit N times, a stacktrace will be logged.

Link: http://lkml.kernel.org/r/0c30c008a0828c660aa0e1bbd3255cf179ed5c30.1382622043.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index 6efa8c2745b5e59bcccc17a7c84558fef8797993..65caee44b4a9088b1f6bd3f95002b2cb44a9d60a 100644 (file)
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -347,6 +347,7 @@ enum event_trigger_type {
        ETT_NONE                = (0),
        ETT_TRACE_ONOFF         = (1 << 0),
        ETT_SNAPSHOT            = (1 << 1),
+       ETT_STACKTRACE          = (1 << 2),
 };
 
 extern void destroy_preds(struct ftrace_event_file *file);

diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index d775c3da180f307d634d056b8208e345f45a6add..a3bd1da90c56605375f5f594bde2b1b251ab551c 100644 (file)
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -780,6 +780,84 @@ static __init int register_trigger_snapshot_cmd(void)
 static __init int register_trigger_snapshot_cmd(void) { return 0; }
 #endif /* CONFIG_TRACER_SNAPSHOT */
 
+#ifdef CONFIG_STACKTRACE
+/*
+ * Skip 3:
+ *   stacktrace_trigger()
+ *   event_triggers_post_call()
+ *   ftrace_raw_event_xxx()
+ */
+#define STACK_SKIP 3
+
+static void
+stacktrace_trigger(struct event_trigger_data *data)
+{
+       trace_dump_stack(STACK_SKIP);
+}
+
+static void
+stacktrace_count_trigger(struct event_trigger_data *data)
+{
+       if (!data->count)
+               return;
+
+       if (data->count != -1)
+               (data->count)--;
+
+       stacktrace_trigger(data);
+}
+
+static int
+stacktrace_trigger_print(struct seq_file *m, struct event_trigger_ops *ops,
+                        struct event_trigger_data *data)
+{
+       return event_trigger_print("stacktrace", m, (void *)data->count,
+                                  data->filter_str);
+}
+
+static struct event_trigger_ops stacktrace_trigger_ops = {
+       .func                   = stacktrace_trigger,
+       .print                  = stacktrace_trigger_print,
+       .init                   = event_trigger_init,
+       .free                   = event_trigger_free,
+};
+
+static struct event_trigger_ops stacktrace_count_trigger_ops = {
+       .func                   = stacktrace_count_trigger,
+       .print                  = stacktrace_trigger_print,
+       .init                   = event_trigger_init,
+       .free                   = event_trigger_free,
+};
+
+static struct event_trigger_ops *
+stacktrace_get_trigger_ops(char *cmd, char *param)
+{
+       return param ? &stacktrace_count_trigger_ops : &stacktrace_trigger_ops;
+}
+
+static struct event_command trigger_stacktrace_cmd = {
+       .name                   = "stacktrace",
+       .trigger_type           = ETT_STACKTRACE,
+       .post_trigger           = true,
+       .func                   = event_trigger_callback,
+       .reg                    = register_trigger,
+       .unreg                  = unregister_trigger,
+       .get_trigger_ops        = stacktrace_get_trigger_ops,
+};
+
+static __init int register_trigger_stacktrace_cmd(void)
+{
+       int ret;
+
+       ret = register_event_command(&trigger_stacktrace_cmd);
+       WARN_ON(ret < 0);
+
+       return ret;
+}
+#else
+static __init int register_trigger_stacktrace_cmd(void) { return 0; }
+#endif /* CONFIG_STACKTRACE */
+
 static __init void unregister_trigger_traceon_traceoff_cmds(void)
 {
        unregister_event_command(&trigger_traceon_cmd);
@@ -804,6 +882,7 @@ __init int register_trigger_cmds(void)
 {
        register_trigger_traceon_traceoff_cmds();
        register_trigger_snapshot_cmd();
+       register_trigger_stacktrace_cmd();
 
        return 0;
 }