[for-next][PATCH 04/10] tracing: Add stacktrace event trigger command

Steven Rostedt
2013-12-23T21:40:44Z

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From: Tom Zanussi <tom.zanussi@linux.intel.com>

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>
---
include/linux/ftrace_event.h | 1 +
kernel/trace/trace_events_trigger.c | 79 +++++++++++++++++++++++++++++++++++++
2 files changed, 80 insertions(+)

diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index 6efa8c2..65caee4 100644
--- 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 d775c3d..a3bd1da 100644
--- 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;
}
--
1.8.4.3