From 19bfbd16a509837bbe57f9c00d6c2a1f0933a5a9 Mon Sep 17 00:00:00 2001 From: Jonathan Rajotte Date: Thu, 7 Oct 2021 16:19:41 -0400 Subject: [PATCH] Fix: sessiond: previously created channel cannot be enabled MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Observed issue ============== A previously created channel cannot be enabled back once a session is started. Cause ===== The check validating that the session was started is to early in the `cmd_enable_channel` function. Solution ======== Move the check at the creation code path when the channel is not found. Known drawbacks ========= None. Signed-off-by: Jonathan Rajotte Change-Id: I8e7d62b7e97246e65f1cf9022270293a6dd34cc9 Signed-off-by: Jérémie Galarneau --- src/bin/lttng-sessiond/cmd.c | 27 ++++++++++++++++++--------- 1 file changed, 18 insertions(+), 9 deletions(-) diff --git a/src/bin/lttng-sessiond/cmd.c b/src/bin/lttng-sessiond/cmd.c index a635c6511..5868c829f 100644 --- a/src/bin/lttng-sessiond/cmd.c +++ b/src/bin/lttng-sessiond/cmd.c @@ -1507,15 +1507,6 @@ int cmd_enable_channel(struct ltt_session *session, rcu_read_lock(); - /* - * Don't try to enable a channel if the session has been started at - * some point in time before. The tracer does not allow it. - */ - if (session->has_been_started) { - ret = LTTNG_ERR_TRACE_ALREADY_STARTED; - goto error; - } - /* * If the session is a live session, remove the switch timer, the * live timer does the same thing but sends also synchronisation @@ -1564,6 +1555,15 @@ int cmd_enable_channel(struct ltt_session *session, kchan = trace_kernel_get_channel_by_name(attr.name, session->kernel_session); if (kchan == NULL) { + /* + * Don't try to create a channel if the session has been started at + * some point in time before. The tracer does not allow it. + */ + if (session->has_been_started) { + ret = LTTNG_ERR_TRACE_ALREADY_STARTED; + goto error; + } + if (session->snapshot.nb_output > 0 || session->snapshot_mode) { /* Enforce mmap output for snapshot sessions. */ @@ -1623,6 +1623,15 @@ int cmd_enable_channel(struct ltt_session *session, uchan = trace_ust_find_channel_by_name(chan_ht, attr.name); if (uchan == NULL) { + /* + * Don't try to create a channel if the session has been started at + * some point in time before. The tracer does not allow it. + */ + if (session->has_been_started) { + ret = LTTNG_ERR_TRACE_ALREADY_STARTED; + goto error; + } + ret = channel_ust_create(usess, &attr, domain->buf_type); if (attr.name[0] != '\0') { usess->has_non_default_channel = 1; -- 2.34.1