NAME¶

tracefs_event_systems, tracefs_system_events, tracefs_iterate_raw_events - Work with trace systems and events.

SYNOPSIS¶

#include <tracefs.h>
char **tracefs_event_systems(const char *tracing_dir);
char **tracefs_system_events(const char *tracing_dir, const char *system);
int tracefs_iterate_raw_events(struct tep_handle *tep, struct tracefs_instance *instance, cpu_set_t *cpus, int cpu_size, int (*callback)(struct tep_event *, struct tep_record *, int, void *), void *callback_context);

DESCRIPTION¶

Trace systems and events related APIs.

The tracefs_event_systems() function returns array of strings with the names of all registered trace systems, located in the given tracing_dir directory. This could be NULL or the location of the tracefs mount point for the trace systems of the local machine, or it may be a path to a copy of the tracefs directory from another machine. The last entry in the array is a NULL pointer. The array must be freed with tracefs_list_free() API.

The tracefs_system_events() function returns array of strings with the names of all registered trace events for given trace system specified by system, located in the given tracing_dir directory. This could be NULL or the location of the tracefs mount point for the trace systems of the local machine, or it may be a path to a copy of the tracefs directory from another machine. The last entry in the array as a NULL pointer. The array must be freed with tracefs_list_free() API.

The tracefs_interate_raw_events() function will read the tracefs raw data buffers and call the specified callback function for every event it encounters. An initialized tep handler is required (See tracefs_local_events(3)). If instance is NULL, then the toplevel tracefs buffer is used, otherwise the buffer for the corresponding instance is read. To filter only on a subset of CPUs, cpus and cpu_size may be set to only call callback with events that occurred on the CPUs specified, otherwise if cpus is NULL then the callback function will be called for all events, and cpu_size is ignored. The callback function will be called with the following parameters: A pointer to a struct tep_event that corresponds to the type of event the record is; The record representing the event; The CPU that the event occurred on; and a pointer to user specified callback_context. If the callback returns non-zero, the iteration stops.

RETURN VALUE¶

The tracefs_event_systems() and _tracefs_system_events() functions return an array of strings. The last element in that array is a NULL pointer. The array must be freed with tracefs_list_free() API. In case of an error, NULL is returned.

The tracefs_iterate_raw_events() function returns -1 in case of an error or 0 otherwise.

EXAMPLE¶

#include <tracefs.h>
char **systems = tracefs_event_systems(NULL);


        if (systems) {


                int i = 0;


                /* Got registered trace systems from the top trace instance */


                while (systems[i]) {


                        char **events = tracefs_system_events(NULL, systems[i]);


                        if (events) {


                                /* Got registered events in system[i] from the top trace instance */


                                int j = 0;


                                while (events[j]) {


                                        /* Got event[j] in system[i] from the top trace instance */


                                        j++;


                                }


                                tracefs_list_free(events);


                        }


                        i++;


                }


                tracefs_list_free(systems);


        }
....
static int records_walk(struct tep_event *tep, struct tep_record *record, int cpu, void *context)
{


        /* Got recorded event on cpu */


        return 0;
}
...
struct tep_event *tep = tracefs_local_events(NULL);


        if (!tep) {


                /* Failed to initialise tep handler with local events */


                ...


        }


        if (tracefs_iterate_raw_events(tep, NULL, NULL, 0, records_walk, NULL) < 0) {


                /* Error walking through the recorded raw events */


        }


        tep_free(tep);

FILES¶

tracefs.h


        Header file to include in order to have access to the library APIs.
-ltracefs


        Linker switch to add when building a program that uses the library.

SEE ALSO¶

libtracefs(3), libtraceevent(3), trace-cmd(1)

AUTHOR¶

Steven Rostedt <rostedt@goodmis.org[1]>
Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>

REPORTING BUGS¶

Report bugs to <linux-trace-devel@vger.kernel.org[3]>

LICENSE¶

libtracefs is Free Software licensed under the GNU LGPL 2.1

RESOURCES¶

https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/

COPYING¶

Copyright (C) 2020 VMware, Inc. Free use of this software is granted under the terms of the GNU Public License (GPL).

NOTES¶

1.

rostedt@goodmis.org

2.

tz.stoyanov@gmail.com

3.

linux-trace-devel@vger.kernel.org