From ccbdaca404a66cf124ec7e4926b1507327f6d165 Mon Sep 17 00:00:00 2001
From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Thu, 12 Dec 2019 11:57:43 -0500
Subject: [PATCH 1/1] sessiond: add clear notifier
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Add a clear notifier array to reply to clients requesting a clear
command.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I422d87b0122b75be47ae5941fed15f09e87460fe
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
---
 src/bin/lttng-sessiond/session.c | 45 ++++++++++++++++++++++++++++++++
 src/bin/lttng-sessiond/session.h |  7 +++++
 2 files changed, 52 insertions(+)

diff --git a/src/bin/lttng-sessiond/session.c b/src/bin/lttng-sessiond/session.c
index 3a537e49e..0da2058fd 100644
--- a/src/bin/lttng-sessiond/session.c
+++ b/src/bin/lttng-sessiond/session.c
@@ -46,6 +46,11 @@ struct ltt_session_destroy_notifier_element {
 	void *user_data;
 };
 
+struct ltt_session_clear_notifier_element {
+	ltt_session_clear_notifier notifier;
+	void *user_data;
+};
+
 /*
  * NOTES:
  *
@@ -769,6 +774,25 @@ void session_notify_destruction(const struct ltt_session *session)
 	}
 }
 
+/*
+ * Fire each clear notifier once, and remove them from the array.
+ */
+void session_notify_clear(struct ltt_session *session)
+{
+	size_t i;
+	const size_t count = lttng_dynamic_array_get_count(
+			&session->clear_notifiers);
+
+	for (i = 0; i < count; i++) {
+		const struct ltt_session_clear_notifier_element *element =
+			lttng_dynamic_array_get_element(
+					&session->clear_notifiers, i);
+
+		element->notifier(session, element->user_data);
+	}
+	lttng_dynamic_array_clear(&session->clear_notifiers);
+}
+
 static
 void session_release(struct urcu_ref *ref)
 {
@@ -831,6 +855,7 @@ void session_release(struct urcu_ref *ref)
 		session->ust_session = NULL;
 	}
 	lttng_dynamic_array_reset(&session->destroy_notifiers);
+	lttng_dynamic_array_reset(&session->clear_notifiers);
 	free(session->last_archived_chunk_name);
 	free(session->base_path);
 	free(session);
@@ -899,6 +924,18 @@ int session_add_destroy_notifier(struct ltt_session *session,
 			&element);
 }
 
+int session_add_clear_notifier(struct ltt_session *session,
+		ltt_session_clear_notifier notifier, void *user_data)
+{
+	const struct ltt_session_clear_notifier_element element = {
+		.notifier = notifier,
+		.user_data = user_data
+	};
+
+	return lttng_dynamic_array_add_element(&session->clear_notifiers,
+			&element);
+}
+
 /*
  * Return a ltt_session structure ptr that matches name. If no session found,
  * NULL is returned. This must be called with the session list lock held using
@@ -990,6 +1027,9 @@ enum lttng_error_code session_create(const char *name, uid_t uid, gid_t gid,
 	lttng_dynamic_array_init(&new_session->destroy_notifiers,
 			sizeof(struct ltt_session_destroy_notifier_element),
 			NULL);
+	lttng_dynamic_array_init(&new_session->clear_notifiers,
+			sizeof(struct ltt_session_clear_notifier_element),
+			NULL);
 	urcu_ref_init(&new_session->ref);
 	pthread_mutex_init(&new_session->lock, NULL);
 
@@ -1184,6 +1224,11 @@ int session_reset_rotation_state(struct ltt_session *session,
 				chunk_id);
 		lttng_trace_chunk_put(session->chunk_being_archived);
 		session->chunk_being_archived = NULL;
+		/*
+		 * Fire the clear reply notifiers if we are completing a clear
+		 * rotation.
+		 */
+		session_notify_clear(session);
 	}
 	return ret;
 }
diff --git a/src/bin/lttng-sessiond/session.h b/src/bin/lttng-sessiond/session.h
index a60354d75..da3805658 100644
--- a/src/bin/lttng-sessiond/session.h
+++ b/src/bin/lttng-sessiond/session.h
@@ -36,6 +36,8 @@ struct ltt_ust_session;
 
 typedef void (*ltt_session_destroy_notifier)(const struct ltt_session *session,
 		void *user_data);
+typedef void (*ltt_session_clear_notifier)(const struct ltt_session *session,
+		void *user_data);
 
 /*
  * Tracing session list
@@ -193,6 +195,7 @@ struct ltt_session {
 	char *last_archived_chunk_name;
 	LTTNG_OPTIONAL(uint64_t) last_archived_chunk_id;
 	struct lttng_dynamic_array destroy_notifiers;
+	struct lttng_dynamic_array clear_notifiers;
 	/* Session base path override. Set non-null. */
 	char *base_path;
 };
@@ -210,6 +213,10 @@ void session_destroy(struct ltt_session *session);
 int session_add_destroy_notifier(struct ltt_session *session,
 		ltt_session_destroy_notifier notifier, void *user_data);
 
+int session_add_clear_notifier(struct ltt_session *session,
+		ltt_session_clear_notifier notifier, void *user_data);
+void session_notify_clear(struct ltt_session *session);
+
 bool session_get(struct ltt_session *session);
 void session_put(struct ltt_session *session);
 
-- 
2.34.1