linux-kernel - [PATCH] ftrace: trigger: Call traceoff trigger after event recorded

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Date:   Fri,  9 Sep 2016 01:05:45 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Tom Zanussi <tom.zanussi@...ux.intel.com>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>
Subject: [PATCH] ftrace: trigger: Call traceoff trigger after event recorded

Call traceoff trigger after the event is recorded.
Since current traceoff trigger is called before recording
the event, we can not know when the trace is off by what event.

Typical usecase of traceoff/traceon trigger is tracing
function calls and trace events between a pair of events.
For example, trace function calls between syscall entry/exit.
In that case, it is useful if we can see the return code
of the target syscall.

Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
---
 kernel/trace/trace_events_trigger.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index a975571..6721a1e8 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -1028,6 +1028,7 @@ static struct event_command trigger_traceon_cmd = {
 static struct event_command trigger_traceoff_cmd = {
 	.name			= "traceoff",
 	.trigger_type		= ETT_TRACE_ONOFF,
+	.flags			= EVENT_CMD_FL_POST_TRIGGER,
 	.func			= event_trigger_callback,
 	.reg			= register_trigger,
 	.unreg			= unregister_trigger,