From: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Date: Tue, 11 Dec 2018 21:54:01 +0000 (-0500)
Subject: Fix: report initialization error of client thread
X-Git-Tag: v2.12.0-rc1~692
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=6cb45e931e18f489f1eb202396148529d86470a6;p=lttng-tools.git

Fix: report initialization error of client thread

The health check tests use the testpoints() in the client thread
to force a pthread_exit() or simulate a catastrophic error within
the client thread.

The testpoints were moved before the signal that the thread's
initialization was completed by recent changes. This caused the
thread to fail to complete its initialization, causing a deadlock
of the session daemon.

This commit reports initialization errors through the
launch_client_thread() function to the "main" thread and shuts down
the session daemon. It also moves the testpoints after the thread's
initialization to respect the test's intent.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
---

diff --git a/src/bin/lttng-sessiond/client.c b/src/bin/lttng-sessiond/client.c
index ea8ffd45f..8cf28a9d6 100644
--- a/src/bin/lttng-sessiond/client.c
+++ b/src/bin/lttng-sessiond/client.c
@@ -40,31 +40,28 @@
 static bool is_root;
 
 static struct thread_state {
-	pthread_cond_t cond;
-	pthread_mutex_t lock;
-	bool is_running;
-} thread_state = {
-	.cond = PTHREAD_COND_INITIALIZER,
-	.lock = PTHREAD_MUTEX_INITIALIZER,
-	.is_running = false
-};
-
-void set_thread_state_running(void)
+	sem_t ready;
+	bool running;
+} thread_state;
+
+static void set_thread_status(bool running)
 {
-	pthread_mutex_lock(&thread_state.lock);
-        thread_state.is_running = true;
-	pthread_cond_broadcast(&thread_state.cond);
-	pthread_mutex_unlock(&thread_state.lock);
+	DBG("Marking client thread's state as %s", running ? "running" : "error");
+	thread_state.running = running;
+	sem_post(&thread_state.ready);
 }
 
-static void wait_thread_state_running(void)
+static bool wait_thread_status(void)
 {
-	pthread_mutex_lock(&thread_state.lock);
-	while (!thread_state.is_running) {
-		pthread_cond_wait(&thread_state.cond,
-				&thread_state.lock);
+	DBG("Waiting for client thread to be ready");
+	sem_wait(&thread_state.ready);
+	if (thread_state.running) {
+		DBG("Client thread is ready");
+	} else {
+		ERR("Initialization of client thread failed");
 	}
-	pthread_mutex_unlock(&thread_state.lock);
+
+	return thread_state.running;
 }
 
 /*
@@ -2071,6 +2068,11 @@ static void cleanup_client_thread(void *data)
 	lttng_pipe_destroy(quit_pipe);
 }
 
+static void thread_init_cleanup(void *data)
+{
+	set_thread_status(false);
+}
+
 /*
  * This thread manage all clients request using the unix client socket for
  * communication.
@@ -2090,6 +2092,7 @@ static void *thread_manage_clients(void *data)
 
 	is_root = (getuid() == 0);
 
+	pthread_cleanup_push(thread_init_cleanup, NULL);
 	client_sock = create_client_sock();
 	if (client_sock < 0) {
 		goto error_listen;
@@ -2127,6 +2130,10 @@ static void *thread_manage_clients(void *data)
 		goto error;
 	}
 
+	/* Set state as running. */
+        set_thread_status(true);
+	pthread_cleanup_pop(0);
+
 	/* This testpoint is after we signal readiness to the parent. */
 	if (testpoint(sessiond_thread_manage_clients)) {
 		goto error;
@@ -2138,9 +2145,6 @@ static void *thread_manage_clients(void *data)
 
 	health_code_update();
 
-	/* Set state as running. */
-        set_thread_state_running();
-
 	while (1) {
 		const struct cmd_completion_handler *cmd_completion_handler;
 
@@ -2362,9 +2366,11 @@ bool shutdown_client_thread(void *thread_data)
 
 struct lttng_thread *launch_client_thread(void)
 {
+	bool thread_running;
 	struct lttng_pipe *client_quit_pipe;
 	struct lttng_thread *thread;
 
+	sem_init(&thread_state.ready, 0, 0);
 	client_quit_pipe = lttng_pipe_open(FD_CLOEXEC);
 	if (!client_quit_pipe) {
 		goto error;
@@ -2383,8 +2389,11 @@ struct lttng_thread *launch_client_thread(void)
 	 * This thread is part of the threads that need to be fully
 	 * initialized before the session daemon is marked as "ready".
 	 */
-	wait_thread_state_running();
-
+	thread_running = wait_thread_status();
+	if (!thread_running) {
+		lttng_thread_put(thread);
+		thread = NULL;
+	}
 	return thread;
 error:
 	cleanup_client_thread(client_quit_pipe);