diff options
| -rw-r--r-- | include/linux/trace_events.h | 5 | ||||
| -rw-r--r-- | kernel/trace/trace_events.c | 85 |
2 files changed, 90 insertions, 0 deletions
diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h index 20948ee56f8c..8d621a73c97e 100644 --- a/include/linux/trace_events.h +++ b/include/linux/trace_events.h @@ -349,6 +349,11 @@ enum { EVENT_FILE_FL_WAS_ENABLED_BIT, }; +extern struct trace_event_file *trace_get_event_file(const char *instance, + const char *system, + const char *event); +extern void trace_put_event_file(struct trace_event_file *file); + /* * Event file flags: * ENABLED - The event is enabled diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index dfb736a964d6..da62472b1297 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -2536,6 +2536,91 @@ find_event_file(struct trace_array *tr, const char *system, const char *event) return file; } +/** + * trace_get_event_file - Find and return a trace event file + * @instance: The name of the trace instance containing the event + * @system: The name of the system containing the event + * @event: The name of the event + * + * Return a trace event file given the trace instance name, trace + * system, and trace event name. If the instance name is NULL, it + * refers to the top-level trace array. + * + * This function will look it up and return it if found, after calling + * trace_array_get() to prevent the instance from going away, and + * increment the event's module refcount to prevent it from being + * removed. + * + * To release the file, call trace_put_event_file(), which will call + * trace_array_put() and decrement the event's module refcount. + * + * Return: The trace event on success, ERR_PTR otherwise. + */ +struct trace_event_file *trace_get_event_file(const char *instance, + const char *system, + const char *event) +{ + struct trace_array *tr = top_trace_array(); + struct trace_event_file *file = NULL; + int ret = -EINVAL; + + if (instance) { + tr = trace_array_find_get(instance); + if (!tr) + return ERR_PTR(-ENOENT); + } else { + ret = trace_array_get(tr); + if (ret) + return ERR_PTR(ret); + } + + mutex_lock(&event_mutex); + + file = find_event_file(tr, system, event); + if (!file) { + trace_array_put(tr); + ret = -EINVAL; + goto out; + } + + /* Don't let event modules unload while in use */ + ret = try_module_get(file->event_call->mod); + if (!ret) { + trace_array_put(tr); + ret = -EBUSY; + goto out; + } + + ret = 0; + out: + mutex_unlock(&event_mutex); + + if (ret) + file = ERR_PTR(ret); + + return file; +} +EXPORT_SYMBOL_GPL(trace_get_event_file); + +/** + * trace_put_event_file - Release a file from trace_get_event_file() + * @file: The trace event file + * + * If a file was retrieved using trace_get_event_file(), this should + * be called when it's no longer needed. It will cancel the previous + * trace_array_get() called by that function, and decrement the + * event's module refcount. + */ +void trace_put_event_file(struct trace_event_file *file) +{ + mutex_lock(&event_mutex); + module_put(file->event_call->mod); + mutex_unlock(&event_mutex); + + trace_array_put(file->tr); +} +EXPORT_SYMBOL_GPL(trace_put_event_file); + #ifdef CONFIG_DYNAMIC_FTRACE /* Avoid typos */ |