+int lttng_session_track_pid(struct lttng_session *session, int pid)
+{
+ int ret;
+
+ if (pid < -1)
+ return -EINVAL;
+ mutex_lock(&sessions_mutex);
+ if (pid == -1) {
+ /* track all pids: destroy tracker. */
+ if (session->pid_tracker) {
+ struct lttng_pid_tracker *lpf;
+
+ lpf = session->pid_tracker;
+ rcu_assign_pointer(session->pid_tracker, NULL);
+ synchronize_trace();
+ lttng_pid_tracker_destroy(lpf);
+ }
+ ret = 0;
+ } else {
+ if (!session->pid_tracker) {
+ struct lttng_pid_tracker *lpf;
+
+ lpf = lttng_pid_tracker_create();
+ if (!lpf) {
+ ret = -ENOMEM;
+ goto unlock;
+ }
+ ret = lttng_pid_tracker_add(lpf, pid);
+ rcu_assign_pointer(session->pid_tracker, lpf);
+ } else {
+ ret = lttng_pid_tracker_add(session->pid_tracker, pid);
+ }
+ }
+unlock:
+ mutex_unlock(&sessions_mutex);
+ return ret;
+}
+
+int lttng_session_untrack_pid(struct lttng_session *session, int pid)
+{
+ int ret;
+
+ if (pid < -1)
+ return -EINVAL;
+ mutex_lock(&sessions_mutex);
+ if (pid == -1) {
+ /* untrack all pids: replace by empty tracker. */
+ struct lttng_pid_tracker *old_lpf = session->pid_tracker;
+ struct lttng_pid_tracker *lpf;
+
+ lpf = lttng_pid_tracker_create();
+ if (!lpf) {
+ ret = -ENOMEM;
+ goto unlock;
+ }
+ rcu_assign_pointer(session->pid_tracker, lpf);
+ synchronize_trace();
+ if (old_lpf)
+ lttng_pid_tracker_destroy(old_lpf);
+ ret = 0;
+ } else {
+ if (!session->pid_tracker) {
+ ret = -ENOENT;
+ goto unlock;
+ }
+ ret = lttng_pid_tracker_del(session->pid_tracker, pid);
+ }
+unlock:
+ mutex_unlock(&sessions_mutex);
+ return ret;
+}
+