From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Thu, 12 Dec 2019 16:55:50 +0000 (-0500)
Subject: sessiond: introduce cleared_after_last_stop
X-Git-Tag: v2.12.0-rc1~132
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=b02f5986773579a5a331d3e108ba52ec9acde2e1;p=lttng-tools.git

sessiond: introduce cleared_after_last_stop

Track whether a session was cleared after the last stop, so
additional clear will be effect-less until it is started again.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Icaa86acab20081b436bd55d026ec79a10c56034b
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
---

diff --git a/src/bin/lttng-sessiond/cmd.c b/src/bin/lttng-sessiond/cmd.c
index 7af855eac..6f824bf31 100644
--- a/src/bin/lttng-sessiond/cmd.c
+++ b/src/bin/lttng-sessiond/cmd.c
@@ -2636,6 +2636,8 @@ int cmd_start_trace(struct ltt_session *session)
 	struct ltt_ust_session *usess;
 	const bool session_rotated_after_last_stop =
 			session->rotated_after_last_stop;
+	const bool session_cleared_after_last_stop =
+			session->cleared_after_last_stop;
 
 	assert(session);
 
@@ -2682,6 +2684,7 @@ int cmd_start_trace(struct ltt_session *session)
 
 	session->active = 1;
 	session->rotated_after_last_stop = false;
+	session->cleared_after_last_stop = false;
 	if (session->output_traces && !session->current_trace_chunk) {
 		if (!session->has_been_started) {
 			struct lttng_trace_chunk *trace_chunk;
@@ -2770,6 +2773,8 @@ error:
 		/* Restore initial state on error. */
 		session->rotated_after_last_stop =
 				session_rotated_after_last_stop;
+		session->cleared_after_last_stop =
+				session_cleared_after_last_stop;
 	}
 	return ret;
 }
@@ -4967,6 +4972,18 @@ int cmd_rotate_session(struct ltt_session *session,
 		cmd_ret = LTTNG_ERR_ROTATION_MULTIPLE_AFTER_STOP;
 		goto end;
 	}
+
+	/*
+	 * After a stop followed by a clear, disallow following rotations a they would
+	 * generate empty chunks.
+	 */
+	if (session->cleared_after_last_stop) {
+		DBG("Session \"%s\" was already cleared after stop, refusing rotation",
+				session->name);
+		cmd_ret = LTTNG_ERR_ROTATION_AFTER_STOP_CLEAR;
+		goto end;
+	}
+
 	if (session->active) {
 		new_trace_chunk = session_create_new_trace_chunk(session, NULL,
 				NULL, NULL);
diff --git a/src/bin/lttng-sessiond/session.h b/src/bin/lttng-sessiond/session.h
index 3625ece6d..a60354d75 100644
--- a/src/bin/lttng-sessiond/session.h
+++ b/src/bin/lttng-sessiond/session.h
@@ -173,6 +173,12 @@ struct ltt_session {
 	 * chunk.
 	 */
 	bool rotated_after_last_stop;
+	/*
+	 * Track whether the session was cleared after last stop. All subsequent
+	 * clear (without prior start) will succeed, but will be effect-less. A
+	 * subsequent rotate (without prior start) will return an error.
+	 */
+	bool cleared_after_last_stop;
 	/*
 	 * Condition and trigger for size-based rotations.
 	 */