From: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Date: Wed, 27 Mar 2019 18:12:47 +0000 (-0400)
Subject: Docs: clarify the meaning of the snapshot_mode flag in ltt_session
X-Git-Tag: v2.12.0-rc1~641
X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=commitdiff_plain;h=92fe5ca1528abfa90cc26f767d274dbff61ffc61;ds=sidebyside

Docs: clarify the meaning of the snapshot_mode flag in ltt_session

The snapshot_mode flag of an ltt_session only affects the default
channel creation attributes. It is not used to prevent the
modification of snapshot outputs.

Since a snapshot session is necessarily in "no-output" mode, it
is redundant to check for this flag in rotation-related commands.

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 d91869fae..033018620 100644
--- a/src/bin/lttng-sessiond/cmd.c
+++ b/src/bin/lttng-sessiond/cmd.c
@@ -4499,8 +4499,7 @@ int cmd_rotate_session(struct ltt_session *session,
 		goto end;
 	}
 
-	if (session->live_timer || session->snapshot_mode ||
-			!session->output_traces) {
+	if (session->live_timer || !session->output_traces) {
 		cmd_ret = LTTNG_ERR_ROTATION_NOT_AVAILABLE;
 		goto end;
 	}
@@ -4849,8 +4848,7 @@ int cmd_rotation_set_schedule(struct ltt_session *session,
 
 	DBG("Cmd rotate set schedule session %s", session->name);
 
-	if (session->live_timer || session->snapshot_mode ||
-			!session->output_traces) {
+	if (session->live_timer || !session->output_traces) {
 		DBG("Failing ROTATION_SET_SCHEDULE command as the rotation feature is not available for this session");
 		ret = LTTNG_ERR_ROTATION_NOT_AVAILABLE;
 		goto end;
diff --git a/src/bin/lttng-sessiond/session.h b/src/bin/lttng-sessiond/session.h
index 6a0da6c16..82e409521 100644
--- a/src/bin/lttng-sessiond/session.h
+++ b/src/bin/lttng-sessiond/session.h
@@ -114,9 +114,11 @@ struct ltt_session {
 	/* Indicate if the session has to output the traces or not. */
 	unsigned int output_traces;
 	/*
-	 * This session is in snapshot mode. This means that every channel enabled
-	 * will be set in overwrite mode and mmap. It is considered exclusively for
-	 * snapshot purposes.
+	 * This session is in snapshot mode. This means that channels enabled
+	 * will be set in overwrite mode by default and must be in mmap
+	 * output mode. Note that snapshots can be taken on a session that
+	 * is not in "snapshot_mode". This parameter only affects channel
+	 * creation defaults.
 	 */
 	unsigned int snapshot_mode;
 	/*