[for-next][PATCH 02/21] tracing: Remove logic for registering multiple event triggers at a time

Steven Rostedt
2022-04-27T19:37:19Z

From: Tom Zanussi <zanussi@kernel.org>

Code for registering triggers assumes it's possible to register more
than one trigger at a time. In fact, it's unimplemented and there
doesn't seem to be a reason to do that.

Remove the n_registered param from event_trigger_register() and fix up
callers.

Doing so simplifies the logic in event_trigger_register to the point
that it just becomes a wrapper calling event_command.reg().

It also removes the problematic call to event_command.unreg() in case
of failure. A new function, event_trigger_unregister() is also added
for callers to call themselves.

The changes to trace_events_hist.c simply allow compilation; a
separate patch follows which updates the hist triggers to work
correctly with the new changes.

Link: https://lkml.kernel.org/r/6149fec7a139d93e84fa4535672fb5bef88006b0.1644010575.git.zanussi@kernel.org

Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
kernel/trace/trace.h | 9 +--
kernel/trace/trace_events_hist.c | 17 ++---
kernel/trace/trace_events_trigger.c | 96 ++++++++++-------------------
3 files changed, 45 insertions(+), 77 deletions(-)

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 07d990270e2a..2bc8036b0659 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1629,10 +1629,11 @@ extern void event_trigger_reset_filter(struct event_command *cmd_ops,
extern int event_trigger_register(struct event_command *cmd_ops,
struct trace_event_file *file,
char *glob,
- char *cmd,
- char *trigger,
- struct event_trigger_data *trigger_data,
- int *n_registered);
+ struct event_trigger_data *trigger_data);
+extern void event_trigger_unregister(struct event_command *cmd_ops,
+ struct trace_event_file *file,
+ char *glob,
+ struct event_trigger_data *trigger_data);

/**
* struct event_trigger_ops - callbacks for trace event triggers
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 44db5ba9cabb..b18d00905eae 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -6287,7 +6287,7 @@ static int event_hist_trigger_parse(struct event_command *cmd_ops,
goto out_free;
}

- cmd_ops->unreg(glob+1, trigger_data, file);
+ event_trigger_unregister(cmd_ops, file, glob+1, trigger_data);
se_name = trace_event_name(file->event_call);
se = find_synth_event(se_name);
if (se)
@@ -6296,13 +6296,10 @@ static int event_hist_trigger_parse(struct event_command *cmd_ops,
goto out_free;
}

- ret = cmd_ops->reg(glob, trigger_data, file);
- /*
- * The above returns on success the # of triggers registered,
- * but if it didn't register any it returns zero. Consider no
- * triggers registered a failure too.
- */
- if (!ret) {
+ ret = event_trigger_register(cmd_ops, file, glob, trigger_data);
+ if (ret)
+ goto out_free;
+ if (ret == 0) {
if (!(attrs->pause || attrs->cont || attrs->clear))
ret = -ENOENT;
goto out_free;
@@ -6331,15 +6328,13 @@ static int event_hist_trigger_parse(struct event_command *cmd_ops,
se = find_synth_event(se_name);
if (se)
se->ref++;
- /* Just return zero, not the number of registered triggers */
- ret = 0;
out:
if (ret == 0)
hist_err_clear();

return ret;
out_unreg:
- cmd_ops->unreg(glob+1, trigger_data, file);
+ event_trigger_unregister(cmd_ops, file, glob+1, trigger_data);
out_free:
if (cmd_ops->set_filter)
cmd_ops->set_filter(NULL, trigger_data, NULL);
diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index 7eb9d04f1c2e..ea13679054a8 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -587,13 +587,12 @@ static int register_trigger(char *glob,
}

list_add_rcu(&data->list, &file->triggers);
- ret++;

update_cond_flag(file);
- if (trace_event_trigger_enable_disable(file, 1) < 0) {
+ ret = trace_event_trigger_enable_disable(file, 1);
+ if (ret < 0) {
list_del_rcu(&data->list);
update_cond_flag(file);
- ret--;
}
out:
return ret;
@@ -927,48 +926,37 @@ void event_trigger_reset_filter(struct event_command *cmd_ops,
* @cmd_ops: The event_command operations for the trigger
* @file: The event file for the trigger's event
* @glob: The trigger command string, with optional remove(!) operator
- * @cmd: The cmd string
- * @param: The param string
* @trigger_data: The trigger_data for the trigger
- * @n_registered: optional outparam, the number of triggers registered
*
* Register an event trigger. The @cmd_ops are used to call the
- * cmd_ops->reg() function which actually does the registration. The
- * cmd_ops->reg() function returns the number of triggers registered,
- * which is assigned to n_registered, if n_registered is non-NULL.
+ * cmd_ops->reg() function which actually does the registration.
*
* Return: 0 on success, errno otherwise
*/
int event_trigger_register(struct event_command *cmd_ops,
struct trace_event_file *file,
char *glob,
- char *cmd,
- char *param,
- struct event_trigger_data *trigger_data,
- int *n_registered)
+ struct event_trigger_data *trigger_data)
{
- int ret;
-
- if (n_registered)
- *n_registered = 0;
-
- ret = cmd_ops->reg(glob, trigger_data, file);
- /*
- * The above returns on success the # of functions enabled,
- * but if it didn't find any functions it returns zero.
- * Consider no functions a failure too.
- */
- if (!ret) {
- cmd_ops->unreg(glob, trigger_data, file);
- ret = -ENOENT;
- } else if (ret > 0) {
- if (n_registered)
- *n_registered = ret;
- /* Just return zero, not the number of enabled functions */
- ret = 0;
- }
+ return cmd_ops->reg(glob, trigger_data, file);
+}

- return ret;
+/**
+ * event_trigger_unregister - unregister an event trigger
+ * @cmd_ops: The event_command operations for the trigger
+ * @file: The event file for the trigger's event
+ * @glob: The trigger command string, with optional remove(!) operator
+ * @trigger_data: The trigger_data for the trigger
+ *
+ * Unregister an event trigger. The @cmd_ops are used to call the
+ * cmd_ops->unreg() function which actually does the unregistration.
+ */
+void event_trigger_unregister(struct event_command *cmd_ops,
+ struct trace_event_file *file,
+ char *glob,
+ struct event_trigger_data *trigger_data)
+{
+ cmd_ops->unreg(glob, trigger_data, file);
}

/*
@@ -1027,7 +1015,7 @@ event_trigger_parse(struct event_command *cmd_ops,
INIT_LIST_HEAD(&trigger_data->named_list);

if (glob[0] == '!') {
- cmd_ops->unreg(glob+1, trigger_data, file);
+ event_trigger_unregister(cmd_ops, file, glob+1, trigger_data);
kfree(trigger_data);
ret = 0;
goto out;
@@ -1062,17 +1050,10 @@ event_trigger_parse(struct event_command *cmd_ops,
out_reg:
/* Up the trigger_data count to make sure reg doesn't free it on failure */
event_trigger_init(trigger_ops, trigger_data);
- ret = cmd_ops->reg(glob, trigger_data, file);
- /*
- * The above returns on success the # of functions enabled,
- * but if it didn't find any functions it returns zero.
- * Consider no functions a failure too.
- */
- if (!ret) {
- cmd_ops->unreg(glob, trigger_data, file);
- ret = -ENOENT;
- } else if (ret > 0)
- ret = 0;
+
+ ret = event_trigger_register(cmd_ops, file, glob, trigger_data);
+ if (ret)
+ goto out_free;

/* Down the counter of trigger_data or free it if not used anymore */
event_trigger_free(trigger_ops, trigger_data);
@@ -1854,7 +1835,7 @@ int event_enable_trigger_parse(struct event_command *cmd_ops,
trigger_data->private_data = enable_data;

if (glob[0] == '!') {
- cmd_ops->unreg(glob+1, trigger_data, file);
+ event_trigger_unregister(cmd_ops, file, glob+1, trigger_data);
kfree(trigger_data);
kfree(enable_data);
ret = 0;
@@ -1901,19 +1882,11 @@ int event_enable_trigger_parse(struct event_command *cmd_ops,
ret = trace_event_enable_disable(event_enable_file, 1, 1);
if (ret < 0)
goto out_put;
- ret = cmd_ops->reg(glob, trigger_data, file);
- /*
- * The above returns on success the # of functions enabled,
- * but if it didn't find any functions it returns zero.
- * Consider no functions a failure too.
- */
- if (!ret) {
- ret = -ENOENT;
- goto out_disable;
- } else if (ret < 0)
+
+ ret = event_trigger_register(cmd_ops, file, glob, trigger_data);
+ if (ret)
goto out_disable;
- /* Just return zero, not the number of enabled functions */
- ret = 0;
+
event_trigger_free(trigger_ops, trigger_data);
out:
return ret;
@@ -1959,13 +1932,12 @@ int event_enable_register_trigger(char *glob,
}

list_add_rcu(&data->list, &file->triggers);
- ret++;

update_cond_flag(file);
- if (trace_event_trigger_enable_disable(file, 1) < 0) {
+ ret = trace_event_trigger_enable_disable(file, 1);
+ if (ret < 0) {
list_del_rcu(&data->list);
update_cond_flag(file);
- ret--;
}
out:
return ret;
--
2.35.1