Fix: use "flush empty" ioctl for snapshots

[lttng-tools.git] / src / common / kernel-consumer / kernel-consumer.c

diff --git a/src/common/kernel-consumer/kernel-consumer.c b/src/common/kernel-consumer/kernel-consumer.c
index 007eef8fcc3d773e71bc7a4c9ffac6ecec11e5dc..57656dcc8794891dd81e8120330353b398bf6a19 100644 (file)
--- a/src/common/kernel-consumer/kernel-consumer.c
+++ b/src/common/kernel-consumer/kernel-consumer.c
@@ -185,13 +185,23 @@ int lttng_kconsumer_snapshot_channel(uint64_t key, char *path,
                                ERR("sending streams sent to relayd");
                                goto end_unlock;
                        }
+                       channel->streams_sent_to_relayd = true;
                }
 
-               ret = kernctl_buffer_flush(stream->wait_fd);
+               ret = kernctl_buffer_flush_empty(stream->wait_fd);
                if (ret < 0) {
-                       ERR("Failed to flush kernel stream");
-                       ret = -errno;
-                       goto end_unlock;
+                       /*
+                        * Doing a buffer flush which does not take into
+                        * account empty packets. This is not perfect
+                        * for stream intersection, but required as a
+                        * fall-back when "flush_empty" is not
+                        * implemented by lttng-modules.
+                        */
+                       ret = kernctl_buffer_flush(stream->wait_fd);
+                       if (ret < 0) {
+                               ERR("Failed to flush kernel stream");
+                               goto end_unlock;
+                       }
                }
 
                ret = lttng_kconsumer_take_snapshot(stream);
@@ -726,6 +736,19 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                                consumer_stream_free(new_stream);
                                goto end_nosignal;
                        }
+
+                       /*
+                        * If adding an extra stream to an already
+                        * existing channel (e.g. cpu hotplug), we need
+                        * to send the "streams_sent" command to relayd.
+                        */
+                       if (channel->streams_sent_to_relayd) {
+                               ret = consumer_send_relayd_streams_sent(
+                                               new_stream->net_seq_idx);
+                               if (ret < 0) {
+                                       goto end_nosignal;
+                               }
+                       }
                }
 
                /* Get the right pipe where the stream will be sent. */
@@ -819,6 +842,7 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                        if (ret < 0) {
                                goto end_nosignal;
                        }
+                       channel->streams_sent_to_relayd = true;
                }
                break;
        }