linux-kernel - [PATCH v2 11/12] tracing: Add generic event-name based remove event method

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Message-Id: <154140869774.17322.8887303560398645347.stgit@devbox>
Date:   Mon,  5 Nov 2018 18:04:57 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Tom Zanussi <tom.zanussi@...ux.intel.com>,
        Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
Subject: [PATCH v2 11/12] tracing: Add generic event-name based remove event method

Add a generic method to remove event from dynamic event
list. This is same as other system under ftrace. You
just need to pass the event name with '!', e.g.

  # echo p:new_grp/new_event _do_fork > dynamic_events

This creates an event, and

  # echo '!p:new_grp/new_event _do_fork' > dynamic_events

Or,

  # echo '!p:new_grp/new_event' > dynamic_events

will remove new_grp/new_event event.

Note that this doesn't check the event prefix (e.g. "p:")
strictly, because the "group/event" name must be unique.

Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
---
  Changes in v2:
  - Instead of checking the given entire line strictly,
    simply checking the event and group name.
---
 kernel/trace/trace_dynevent.c |   15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/trace_dynevent.c b/kernel/trace/trace_dynevent.c
index f17a887abb66..dd1f43588d70 100644
--- a/kernel/trace/trace_dynevent.c
+++ b/kernel/trace/trace_dynevent.c
@@ -37,10 +37,17 @@ int dyn_event_release(int argc, char **argv, struct dyn_event_operations *type)
 	char *system = NULL, *event, *p;
 	int ret = -ENOENT;
 
-	if (argv[0][1] != ':')
-		return -EINVAL;
+	if (argv[0][0] == '-') {
+		if (argv[0][1] != ':')
+			return -EINVAL;
+		event = &argv[0][2];
+	} else {
+		event = strchr(argv[0], ':');
+		if (!event)
+			return -EINVAL;
+		event++;
+	}
 
-	event = &argv[0][2];
 	p = strchr(event, '/');
 	if (p) {
 		system = event;
@@ -69,7 +76,7 @@ static int create_dyn_event(int argc, char **argv)
 	struct dyn_event_operations *ops;
 	int ret;
 
-	if (argv[0][0] == '-')
+	if (argv[0][0] == '-' || argv[0][0] == '!')
 		return dyn_event_release(argc, argv, NULL);
 
 	mutex_lock(&dyn_event_ops_mutex);