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

From: Masami Hiramatsu
Date: Mon Nov 05 2018 - 04:05:22 EST


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@xxxxxxxxxx>
---
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);