rcu_read_lock();
+ /*
+ * The ringbuffer (both in user space and kernel) behave badly in overwrite
+ * mode and with less than 2 subbuf so block it right away and send back an
+ * invalid attribute error.
+ */
+ if (attr->attr.overwrite && attr->attr.num_subbuf < 2) {
+ ret = LTTNG_ERR_INVALID;
+ goto error;
+ }
+
switch (domain->type) {
case LTTNG_DOMAIN_KERNEL:
{
int cmd_start_trace(struct ltt_session *session)
{
int ret;
+ unsigned long nb_chan = 0;
struct ltt_kernel_session *ksession;
struct ltt_ust_session *usess;
goto error;
}
+ /*
+ * Starting a session without channel is useless since after that it's not
+ * possible to enable channel thus inform the client.
+ */
+ if (usess && usess->domain_global.channels) {
+ nb_chan += lttng_ht_get_count(usess->domain_global.channels);
+ }
+ if (ksession) {
+ nb_chan += ksession->channel_count;
+ }
+ if (!nb_chan) {
+ ret = LTTNG_ERR_NO_CHANNEL;
+ goto error;
+ }
+
session->enabled = 1;
/* Kernel tracing */
}
}
+ /*
+ * Make sure to set the session in output mode after we set URI since a
+ * session can be created without URL (thus flagged in no output mode).
+ */
+ session->output_traces = 1;
+ if (ksess) {
+ ksess->output_traces = 1;
+ } else if (usess) {
+ usess->output_traces = 1;
+ }
+
/* All good! */
ret = LTTNG_OK;
if (session->enabled) {
ret = LTTNG_ERR_SESSION_STARTED;
goto error;
+ } else {
+ /*
+ * If stopped, just make sure we've started before else the above call
+ * will always send that there is data pending.
+ *
+ * The consumer assumes that when the data pending command is received,
+ * the trace has been started before or else no output data is written
+ * by the streams which is a condition for data pending. So, this is
+ * *VERY* important that we don't ask the consumer before a start
+ * trace.
+ */
+ if (!session->started) {
+ ret = 0;
+ goto error;
+ }
}
if (ksess && ksess->consumer) {