From 1f4962443f25c371e4b54e97f9eb867d67cbf88e Mon Sep 17 00:00:00 2001 From: =?utf8?q?J=C3=A9r=C3=A9mie=20Galarneau?= Date: Mon, 18 Nov 2019 16:01:44 -0500 Subject: [PATCH] Fix: sessiond: no rotation performed from null chunk to new chunk MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit The session daemon must rotate from a null trace chunk to a new trace chunk when a session's current trace chunk is null. This situation happens when a session is stopped, rotated, and started again. This bug leaves existing streams in the "null" trace chunk and causes the relay daemon to report a protocol error on the reception of the first data packet following such a start. Signed-off-by: Jérémie Galarneau --- src/bin/lttng-sessiond/cmd.c | 81 ++++++++++++++++++++++++++++-------- 1 file changed, 64 insertions(+), 17 deletions(-) diff --git a/src/bin/lttng-sessiond/cmd.c b/src/bin/lttng-sessiond/cmd.c index be493fd8a..5a122d8d3 100644 --- a/src/bin/lttng-sessiond/cmd.c +++ b/src/bin/lttng-sessiond/cmd.c @@ -2572,6 +2572,8 @@ int cmd_start_trace(struct ltt_session *session) unsigned long nb_chan = 0; struct ltt_kernel_session *ksession; struct ltt_ust_session *usess; + const bool session_rotated_after_last_stop = + session->rotated_after_last_stop; assert(session); @@ -2585,6 +2587,22 @@ int cmd_start_trace(struct ltt_session *session) goto error; } + if (session->rotation_state == LTTNG_ROTATION_STATE_ONGOING && + !session->current_trace_chunk) { + /* + * A rotation was launched while the session was stopped and + * it has not been completed yet. It is not possible to start + * the session since starting the session here would require a + * rotation from "NULL" to a new trace chunk. That rotation + * would overlap with the ongoing rotation, which is not + * supported. + */ + WARN("Refusing to start session \"%s\" as a rotation launched after the last \"stop\" is still ongoing", + session->name); + ret = LTTNG_ERR_ROTATION_PENDING; + goto error; + } + /* * Starting a session without channel is useless since after that it's not * possible to enable channel thus inform the client. @@ -2600,21 +2618,45 @@ int cmd_start_trace(struct ltt_session *session) goto error; } + session->active = 1; + session->rotated_after_last_stop = false; if (session->output_traces && !session->current_trace_chunk) { - struct lttng_trace_chunk *trace_chunk; + if (!session->has_been_started) { + struct lttng_trace_chunk *trace_chunk; - trace_chunk = session_create_new_trace_chunk( - session, NULL, NULL, NULL); - if (!trace_chunk) { - ret = LTTNG_ERR_CREATE_DIR_FAIL; - goto error; - } - assert(!session->current_trace_chunk); - ret = session_set_trace_chunk(session, trace_chunk, NULL); - lttng_trace_chunk_put(trace_chunk); - if (ret) { - ret = LTTNG_ERR_CREATE_TRACE_CHUNK_FAIL_CONSUMER; - goto error; + DBG("Creating initial trace chunk of session \"%s\"", + session->name); + trace_chunk = session_create_new_trace_chunk( + session, NULL, NULL, NULL); + if (!trace_chunk) { + ret = LTTNG_ERR_CREATE_DIR_FAIL; + goto error; + } + assert(!session->current_trace_chunk); + ret = session_set_trace_chunk(session, trace_chunk, + NULL); + lttng_trace_chunk_put(trace_chunk); + if (ret) { + ret = LTTNG_ERR_CREATE_TRACE_CHUNK_FAIL_CONSUMER; + goto error; + } + } else { + DBG("Rotating session \"%s\" from its current \"NULL\" trace chunk to a new chunk", + session->name); + /* + * Rotate existing streams into the new chunk. + * This is a "quiet" rotation has no client has + * explicitly requested this operation. + * + * There is also no need to wait for the rotation + * to complete as it will happen immediately. No data + * was produced as the session was stopped, so the + * rotation should happen on reception of the command. + */ + ret = cmd_rotate_session(session, NULL, true); + if (ret != LTTNG_OK) { + goto error; + } } } @@ -2637,10 +2679,6 @@ int cmd_start_trace(struct ltt_session *session) } } - /* Flag this after a successful start. */ - session->has_been_started = 1; - session->active = 1; - /* * Clear the flag that indicates that a rotation was done while the * session was stopped. @@ -2661,6 +2699,15 @@ int cmd_start_trace(struct ltt_session *session) ret = LTTNG_OK; error: + if (ret == LTTNG_OK) { + /* Flag this after a successful start. */ + session->has_been_started |= 1; + } else { + session->active = 0; + /* Restore initial state on error. */ + session->rotated_after_last_stop = + session_rotated_after_last_stop; + } return ret; } -- 2.34.1