From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx>
Add tracefs_follow_event() API that allows to only receive a callback for
a specific event.
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
---
Documentation/libtracefs-iterator.txt | 129 ++++++++++++++++++--------
Documentation/libtracefs.txt | 6 ++
include/tracefs-local.h | 10 ++
include/tracefs.h | 6 ++
src/tracefs-events.c | 101 +++++++++++++++++++-
5 files changed, 209 insertions(+), 43 deletions(-)
diff --git a/Documentation/libtracefs-iterator.txt b/Documentation/libtracefs-iterator.txt
index a291f8f169ba..f53991f5cebe 100644
--- a/Documentation/libtracefs-iterator.txt
+++ b/Documentation/libtracefs-iterator.txt
@@ -3,7 +3,7 @@ libtracefs(3)
NAME
----
-tracefs_iterate_raw_events, tracefs_iterate_stop - Iterate over events in the ring buffer
+tracefs_iterate_raw_events, tracefs_iterate_stop, tracefs_follow_event - Iterate over events in the ring buffer
SYNOPSIS
--------
@@ -17,6 +17,12 @@ int *tracefs_iterate_raw_events*(struct tep_handle pass:[*]_tep_, struct tracefs
void pass:[*]_callback_context_);
void *tracefs_iterate_stop*(struct tracefs_instance pass:[*]_instance_);
+int *tracefs_follow_event*(struct tep_handle pass:[*]_tep_, struct tracefs_instance pass:[*]_instance_,
+ const char pass:[*]_system_, const char pass:[*]_event_name_,
+ int (pass:[*]_callback_)(struct tep_event pass:[*],
+ struct tep_record pass:[*],
+ int, void pass:[*]),
+ void pass:[*]_callback_data_):
--
DESCRIPTION
@@ -43,6 +49,14 @@ to halt. This can be called from either a callback that is called by
the iterator (even though a return of non-zero will stop it), or from another
thread.
+The *tracefs_follow_event()* is used with *tracefs_iterate_raw_events()* but
+intead of the callback being called for every event, it is only called for the
+specified _system_ / _event_name_ given to the function. The _callback_ is the
+same as for *tracefs_iterate_raw_events()*, and the passed in _callback_context_
+will be passed to the _callback_ as well. Note, if it returns something other
+than 0, it will stop the loop before the _callback_ of *tracefs_iterate_raw_events()*
+is called.
+
RETURN VALUE
------------
The *tracefs_iterate_raw_events()* function returns -1 in case of an error or
@@ -52,56 +66,89 @@ EXAMPLE
-------
[source,c]
--
+#include <unistd.h>
#include <tracefs.h>
+#include <stdbool.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)
+struct my_struct {
+ bool stopped;
+};
+
+static int callback(struct tep_event *event, struct tep_record *record,
+ int cpu, void *data)
{
- /* Got recorded event on cpu */
+ struct my_struct *my_data = data;
+ static struct trace_seq seq;
+ static int counter;
+
+ if (counter++ > 10000) {
+ my_data->stopped = true;
+ return 1;
+ }
+
+ if (!seq.buffer)
+ trace_seq_init(&seq);
+
+ tep_print_event(event->tep, &seq, record, "%16s-%-5d [%03d] %6.1000d %s: %s\n",
+ TEP_PRINT_COMM, TEP_PRINT_PID, TEP_PRINT_CPU,
+ TEP_PRINT_TIME, TEP_PRINT_NAME, TEP_PRINT_INFO);
+ trace_seq_terminate(&seq);
+ trace_seq_do_printf(&seq);
+ trace_seq_reset(&seq);
return 0;
}
-...
-struct tep_handle *tep = tracefs_local_events(NULL);
- if (!tep) {
- /* Failed to initialise tep handler with local events */
- ...
+static int sched_callback(struct tep_event *event, struct tep_record *record,
+ int cpu, void *data)
+{
+ static struct tep_format_field *prev_pid;
+ static struct tep_format_field *next_pid;
+ unsigned long long pid;
+ int this_pid = *(int *)data;
+
+ if (!prev_pid) {
+ prev_pid = tep_find_field(event, "prev_pid");
+ next_pid = tep_find_field(event, "next_pid");
+ if (!prev_pid || !next_pid) {
+ fprintf(stderr, "No pid fields??\n");
+ return -1;
+ }
}
- errno = 0;
- ret = tracefs_event_enable(NULL, "sched", NULL);
- if (ret < 0 && !errno)
- printf("Could not find 'sched' events\n");
- tracefs_event_enable(NULL, "irq", "irq_handler_\(enter\|exit\)");
+ tep_read_number_field(prev_pid, record->data, &pid);
+ if (pid == this_pid)
+ printf("WE ARE LEAVING!\n");
+ tep_read_number_field(next_pid, record->data, &pid);
+ if (pid == this_pid)
+ printf("WE ARE ARRIVING!\n");
+ return 0;
+}
- if (tracefs_iterate_raw_events(tep, NULL, NULL, 0, records_walk, NULL) < 0) {
- /* Error walking through the recorded raw events */
- }
+int main (int argc, char **argv, char **env)
+{
+ struct tep_handle *tep;
+ struct tracefs_instance *instance;
+ struct my_struct my_data = { .stopped = false };
+ int this_pid = getpid();
+
+ instance = tracefs_instance_create("my-buffer");
+ if (!instance)
+ return -1;
+
+ tracefs_event_enable(instance, "sched", NULL);
+ sleep(1);
+ tracefs_event_disable(instance, NULL, NULL);
+ tep = tracefs_local_events(NULL);
+ tep_load_plugins(tep);
+ tracefs_follow_event(tep, instance, "sched", "sched_switch", sched_callback, &this_pid);
+ tracefs_iterate_raw_events(tep, instance, NULL, 0, callback, &my_data);
+ tracefs_instance_destroy(instance);
+
+ if (my_data.stopped)
+ printf("stopped!\n");
- /* Disable all events */
- tracefs_event_disable(NULL, NULL, NULL);
- tep_free(tep);
+ return 0;
+}
--
FILES
-----
diff --git a/Documentation/libtracefs.txt b/Documentation/libtracefs.txt
index cc53388438e5..e4178062d319 100644
--- a/Documentation/libtracefs.txt
+++ b/Documentation/libtracefs.txt
@@ -60,6 +60,12 @@ Trace events:
const char pass:[*]_system_, const char pass:[*]_event_);
int *tracefs_iterate_raw_events*(struct tep_handle pass:[*]_tep_, struct tracefs_instance pass:[*]_instance_, cpu_set_t pass:[*]_cpus_, int _cpu_size_, int (pass:[*]_callback_)(struct tep_event pass:[*], struct tep_record pass:[*], int, void pass:[*]), void pass:[*]_callback_context_);
void *tracefs_iterate_stop*(struct tracefs_instance pass:[*]_instance_);
+ int *tracefs_follow_event*(struct tep_handle pass:[*]_tep_, struct tracefs_instance pass:[*]_instance_,
+ const char pass:[*]_system_, const char pass:[*]_event_name_,
+ int (pass:[*]_callback_)(struct tep_event pass:[*],
+ struct tep_record pass:[*],
+ int, void pass:[*]),
+ void pass:[*]_callback_data_):
struct tep_handle pass:[*]*tracefs_local_events*(const char pass:[*]_tracing_dir_);
struct tep_handle pass:[*]*tracefs_local_events_system*(const char pass:[*]_tracing_dir_, const char pass:[*] const pass:[*]_sys_names_);
int *tracefs_fill_local_events*(const char pass:[*]_tracing_dir_, struct tep_handle pass:[*]_tep_, int pass:[*]_parsing_failures_);
diff --git a/include/tracefs-local.h b/include/tracefs-local.h
index 1286cbf800a2..4c636be8a1fe 100644
--- a/include/tracefs-local.h
+++ b/include/tracefs-local.h
@@ -23,9 +23,18 @@ struct tracefs_options_mask {
unsigned long long mask;
};
+struct follow_event {
+ struct tep_event *event;
+ void *callback_data;
+ int (*callback)(struct tep_event *,
+ struct tep_record *,
+ int, void *);
+};
+
struct tracefs_instance {
struct tracefs_options_mask supported_opts;
struct tracefs_options_mask enabled_opts;
+ struct follow_event *followers;
char *trace_dir;
char *name;
pthread_mutex_t lock;
@@ -35,6 +44,7 @@ struct tracefs_instance {
int ftrace_notrace_fd;
int ftrace_marker_fd;
int ftrace_marker_raw_fd;
+ int nr_followers;
bool pipe_keep_going;
bool iterate_keep_going;
};
diff --git a/include/tracefs.h b/include/tracefs.h
index 10f84a25c31e..cb64e098883a 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -126,6 +126,12 @@ int tracefs_iterate_raw_events(struct tep_handle *tep,
int, void *),
void *callback_context);
void tracefs_iterate_stop(struct tracefs_instance *instance);
+int tracefs_follow_event(struct tep_handle *tep, struct tracefs_instance *instance,
+ const char *system, const char *event_name,
+ int (*callback)(struct tep_event *,
+ struct tep_record *,
+ int, void *),
+ void *callback_data);
char *tracefs_event_get_file(struct tracefs_instance *instance,
const char *system, const char *event,
diff --git a/src/tracefs-events.c b/src/tracefs-events.c
index 592b1a01fea4..abd97da8abbd 100644
--- a/src/tracefs-events.c
+++ b/src/tracefs-events.c
@@ -20,6 +20,9 @@
#include "tracefs.h"
#include "tracefs-local.h"
+static struct follow_event *root_followers;
+static int nr_root_followers;
+
struct cpu_iterate {
struct tracefs_cpu *tcpu;
struct tep_record record;
@@ -117,7 +120,36 @@ int read_next_record(struct tep_handle *tep, struct cpu_iterate *cpu)
return -1;
}
-static int read_cpu_pages(struct tep_handle *tep, struct cpu_iterate *cpus, int count,
+static int call_followers(struct tracefs_instance *instance,
+ struct tep_event *event, struct tep_record *record, int cpu)
+{
+ struct follow_event *followers;
+ int nr_followers;
+ int ret = 0;
+ int i;
+
+ if (instance) {
+ followers = instance->followers;
+ nr_followers = instance->nr_followers;
+ } else {
+ followers = root_followers;
+ nr_followers = nr_root_followers;
+ }
+
+ if (!followers)
+ return 0;
+
+ for (i = 0; i < nr_followers; i++) {
+ if (followers[i].event == event)
+ ret |= followers[i].callback(event, record,
+ cpu, followers[i].callback_data);
+ }
+
+ return ret;
+}
+
+static int read_cpu_pages(struct tep_handle *tep, struct tracefs_instance *instance,
+ struct cpu_iterate *cpus, int count,
int (*callback)(struct tep_event *,
struct tep_record *,
int, void *),
@@ -143,6 +175,8 @@ static int read_cpu_pages(struct tep_handle *tep, struct cpu_iterate *cpus, int
j = i;
}
if (j < count) {
+ if (call_followers(instance, cpus[j].event, &cpus[j].record, cpus[j].cpu))
+ break;
if (callback(cpus[j].event, &cpus[j].record, cpus[j].cpu, callback_context))
break;
cpus[j].event = NULL;
@@ -205,6 +239,69 @@ static int open_cpu_files(struct tracefs_instance *instance, cpu_set_t *cpus,
return -1;
}
+/**
+ * tracefs_follow_event - Add callback for specific events for iterators
+ * @tep: a handle to the trace event parser context
+ * @instance: The instance to follow
+ * @system: The system of the event to track
+ * @event_name: The name of the event to track
+ * @callback: The function to call when the event is hit in an iterator
+ * @callback_data: The data to pass to @callback
+ *
+ * This attaches a callback to an @instance or the root instance if @instance
+ * is NULL, where if tracefs_iterate_raw_events() is called, that if the specified
+ * event is hit, it will call @callback, with the following parameters:
+ * @event: The event pointer that was found by @system and @event_name.
+ * @record; The event instance of @event.
+ * @cpu: The cpu that the event happened on.
+ * @callback_data: The same as @callback_data passed to the function.
+ *
+ * Returns 0 on success and -1 on error.
+ */
+int tracefs_follow_event(struct tep_handle *tep, struct tracefs_instance *instance,
+ const char *system, const char *event_name,
+ int (*callback)(struct tep_event *,
+ struct tep_record *,
+ int, void *),
+ void *callback_data)
+{
+ struct follow_event **followers;
+ struct follow_event *follower;
+ struct follow_event follow;
+ int *nr_followers;
+
+ if (!tep) {
+ errno = EINVAL;
+ return -1;
+ }
+
+ follow.event = tep_find_event_by_name(tep, system, event_name);
+ if (!follow.event) {
+ errno = ENOENT;
+ return -1;
+ }
+
+ follow.callback = callback;
+ follow.callback_data = callback_data;
+
+ if (instance) {
+ followers = &instance->followers;
+ nr_followers = &instance->nr_followers;
+ } else {
+ followers = &root_followers;
+ nr_followers = &nr_root_followers;
+ }
+ follower = realloc(*followers, sizeof(*follower) *
+ ((*nr_followers) + 1));
+ if (!follower)
+ return -1;
+
+ *followers = follower;
+ follower[(*nr_followers)++] = follow;
+
+ return 0;
+}
+
static bool top_iterate_keep_going;
/*
@@ -247,7 +344,7 @@ int tracefs_iterate_raw_events(struct tep_handle *tep,
ret = open_cpu_files(instance, cpus, cpu_size, &all_cpus, &count);
if (ret < 0)
goto out;
- ret = read_cpu_pages(tep, all_cpus, count,
+ ret = read_cpu_pages(tep, instance, all_cpus, count,
callback, callback_context,
keep_going);
--
2.35.1
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