+/*
+ * create_posix_shm is never called concurrently within a process.
+ */
+static
+int create_posix_shm(void)
+{
+ char tmp_name[NAME_MAX];
+ int shmfd, ret;
+
+ ret = snprintf(tmp_name, NAME_MAX, "/ust-shm-consumer-%d", getpid());
+ if (ret < 0) {
+ PERROR("snprintf");
+ return -1;
+ }
+ /*
+ * Allocate shm, and immediately unlink its shm oject, keeping
+ * only the file descriptor as a reference to the object.
+ * We specifically do _not_ use the / at the beginning of the
+ * pathname so that some OS implementations can keep it local to
+ * the process (POSIX leaves this implementation-defined).
+ */
+ shmfd = shm_open(tmp_name, O_CREAT | O_EXCL | O_RDWR, 0700);
+ if (shmfd < 0) {
+ PERROR("shm_open");
+ goto error_shm_open;
+ }
+ ret = shm_unlink(tmp_name);
+ if (ret < 0 && errno != ENOENT) {
+ PERROR("shm_unlink");
+ goto error_shm_release;
+ }
+ return shmfd;
+
+error_shm_release:
+ ret = close(shmfd);
+ if (ret) {
+ PERROR("close");
+ }
+error_shm_open:
+ return -1;
+}
+
+static int open_ust_stream_fd(struct lttng_consumer_channel *channel,
+ struct ustctl_consumer_channel_attr *attr,
+ int cpu)
+{
+ char shm_path[PATH_MAX];
+ int ret;
+
+ if (!channel->shm_path[0]) {
+ return create_posix_shm();
+ }
+ ret = get_stream_shm_path(shm_path, channel->shm_path, cpu);
+ if (ret) {
+ goto error_shm_path;
+ }
+ return run_as_open(shm_path,
+ O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR,
+ channel->uid, channel->gid);
+
+error_shm_path:
+ return -1;
+}
+