Fix multi-session UST handling combined with shm fd teardown

[lttng-tools.git] / lttng-sessiond / ust-consumer.c

diff --git a/lttng-sessiond/ust-consumer.c b/lttng-sessiond/ust-consumer.c
index ca008d4adf65d0165d3eaca6f06f149361081594..46558417ecc2c47b295a7613ae35c7da7c9412d0 100644 (file)
--- a/lttng-sessiond/ust-consumer.c
+++ b/lttng-sessiond/ust-consumer.c
@@ -38,7 +38,7 @@ static int send_channel_streams(int sock,
 {
        int ret, fd;
        struct lttcomm_consumer_msg lum;
-       struct ltt_ust_stream *stream;
+       struct ltt_ust_stream *stream, *tmp;
 
        DBG("Sending streams of channel %s to UST consumer", uchan->name);
 
@@ -46,8 +46,11 @@ static int send_channel_streams(int sock,
        lum.cmd_type = LTTNG_CONSUMER_ADD_CHANNEL;
 
        /*
-        * We need to keep shm_fd open to make sure this key stays unique within
-        * the session daemon.
+        * We need to keep shm_fd open while we transfer the stream file
+        * descriptors to make sure this key stays unique within the
+        * session daemon. We can free the channel shm_fd without
+        * problem after we finished sending stream fds for that
+        * channel.
         */
        lum.u.channel.channel_key = uchan->obj->shm_fd;
        lum.u.channel.max_sb_size = uchan->attr.subbuf_size;
@@ -65,7 +68,7 @@ static int send_channel_streams(int sock,
                goto error;
        }
 
-       cds_list_for_each_entry(stream, &uchan->streams.head, list) {
+       cds_list_for_each_entry_safe(stream, tmp, &uchan->streams.head, list) {
                int fds[2];
 
                if (!stream->obj->shm_fd) {
@@ -97,7 +100,18 @@ static int send_channel_streams(int sock,
                        perror("send consumer stream ancillary data");
                        goto error;
                }
+
+               /*
+                * We release the stream object here, as we have passed
+                * it to the consumer.
+                */
+               /* Ensure we don't let the app know (sock = -1). */
+               ustctl_release_object(-1, stream->obj);
+               cds_list_del(&stream->list);
+               free(stream);
        }
+       /* Ensure we don't let the app know (sock = -1). */
+       ustctl_release_object(-1, uchan->obj);
 
        DBG("consumer channel streams sent");
 
@@ -165,6 +179,10 @@ int ust_consumer_send_session(int consumer_fd, struct ust_app_session *usess)
                        perror("send consumer stream");
                        goto error;
                }
+               /* Metadata fds passed to consumer, release them. */
+               /* Ensure we don't let the app know (sock = -1). */
+               ustctl_release_object(-1, usess->metadata->stream_obj);
+               ustctl_release_object(-1, usess->metadata->obj);
        }
 
        /* Send each channel fd streams of session */