X-Git-Url: http://git.lttng.org/?a=blobdiff_plain;f=liblttng-ust%2Flttng-ust-comm.c;h=8c864f8ce595621434cfac4a08dec1aa705d5671;hb=3b8b68e73ec9b2b3cf550048046d3f7f69050688;hp=e3afe6af562cb8a22207ca90210b3450b8d2453d;hpb=e6973a8909554c1b1d812f4f07d8806b87cad394;p=lttng-ust.git

diff --git a/liblttng-ust/lttng-ust-comm.c b/liblttng-ust/lttng-ust-comm.c
index e3afe6af..8c864f8c 100644
--- a/liblttng-ust/lttng-ust-comm.c
+++ b/liblttng-ust/lttng-ust-comm.c
@@ -78,6 +78,12 @@ static sem_t constructor_wait;
  */
 static int sem_count = { 2 };
 
+/*
+ * Counting nesting within lttng-ust. Used to ensure that calling fork()
+ * from liblttng-ust does not execute the pre/post fork handlers.
+ */
+static int __thread lttng_ust_nest_count;
+
 /*
  * Info about socket and associated listener thread.
  */
@@ -325,14 +331,20 @@ end:
 	     || lum->cmd == LTTNG_UST_CHANNEL
 	     || lum->cmd == LTTNG_UST_METADATA)
 			&& lur.ret_code == USTCOMM_OK) {
+		int sendret = 0;
+
 		/* we also need to send the file descriptors. */
 		ret = ustcomm_send_fds_unix_sock(sock,
 			&shm_fd, &shm_fd,
 			1, sizeof(int));
 		if (ret < 0) {
 			perror("send shm_fd");
-			goto error;
+			sendret = ret;
 		}
+		/*
+		 * The sessiond expects 2 file descriptors, even upon
+		 * error.
+		 */
 		ret = ustcomm_send_fds_unix_sock(sock,
 			&wait_fd, &wait_fd,
 			1, sizeof(int));
@@ -340,6 +352,10 @@ end:
 			perror("send wait_fd");
 			goto error;
 		}
+		if (sendret) {
+			ret = sendret;
+			goto error;
+		}
 	}
 	/*
 	 * We still have the memory map reference, and the fds have been
@@ -459,7 +475,9 @@ int get_wait_shm(struct sock_info *sock_info, size_t mmap_size)
 	 * If the open failed because the file did not exist, try
 	 * creating it ourself.
 	 */
+	lttng_ust_nest_count++;
 	pid = fork();
+	lttng_ust_nest_count--;
 	if (pid > 0) {
 		int status;
 
@@ -827,6 +845,7 @@ int get_timeout(struct timespec *constructor_timeout)
 void __attribute__((constructor)) lttng_ust_init(void)
 {
 	struct timespec constructor_timeout;
+	sigset_t sig_all_blocked, orig_parent_mask;
 	int timeout_mode;
 	int ret;
 
@@ -863,16 +882,39 @@ void __attribute__((constructor)) lttng_ust_init(void)
 	if (ret) {
 		ERR("Error setting up to local apps");
 	}
-	ret = pthread_create(&local_apps.ust_listener, NULL,
-			ust_listener_thread, &local_apps);
 
+	/* A new thread created by pthread_create inherits the signal mask
+	 * from the parent. To avoid any signal being received by the
+	 * listener thread, we block all signals temporarily in the parent,
+	 * while we create the listener thread.
+	 */
+	sigfillset(&sig_all_blocked);
+	ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_parent_mask);
+	if (ret) {
+		ERR("pthread_sigmask: %s", strerror(ret));
+	}
+
+	ret = pthread_create(&global_apps.ust_listener, NULL,
+			ust_listener_thread, &global_apps);
+	if (ret) {
+		ERR("pthread_create global: %s", strerror(ret));
+	}
 	if (local_apps.allowed) {
-		ret = pthread_create(&global_apps.ust_listener, NULL,
-				ust_listener_thread, &global_apps);
+		ret = pthread_create(&local_apps.ust_listener, NULL,
+				ust_listener_thread, &local_apps);
+		if (ret) {
+			ERR("pthread_create local: %s", strerror(ret));
+		}
 	} else {
 		handle_register_done(&local_apps);
 	}
 
+	/* Restore original signal mask in parent */
+	ret = pthread_sigmask(SIG_SETMASK, &orig_parent_mask, NULL);
+	if (ret) {
+		ERR("pthread_sigmask: %s", strerror(ret));
+	}
+
 	switch (timeout_mode) {
 	case 1:	/* timeout wait */
 		do {
@@ -946,12 +988,14 @@ void __attribute__((destructor)) lttng_ust_exit(void)
 	/* cancel threads */
 	ret = pthread_cancel(global_apps.ust_listener);
 	if (ret) {
-		ERR("Error cancelling global ust listener thread");
+		ERR("Error cancelling global ust listener thread: %s",
+			strerror(ret));
 	}
 	if (local_apps.allowed) {
 		ret = pthread_cancel(local_apps.ust_listener);
 		if (ret) {
-			ERR("Error cancelling local ust listener thread");
+			ERR("Error cancelling local ust listener thread: %s",
+				strerror(ret));
 		}
 	}
 	/*
@@ -983,6 +1027,8 @@ void ust_before_fork(sigset_t *save_sigset)
 	sigset_t all_sigs;
 	int ret;
 
+	if (lttng_ust_nest_count)
+		return;
 	/* Disable signals */
 	sigfillset(&all_sigs);
 	ret = sigprocmask(SIG_BLOCK, &all_sigs, save_sigset);
@@ -1008,6 +1054,8 @@ static void ust_after_fork_common(sigset_t *restore_sigset)
 
 void ust_after_fork_parent(sigset_t *restore_sigset)
 {
+	if (lttng_ust_nest_count)
+		return;
 	DBG("process %d", getpid());
 	rcu_bp_after_fork_parent();
 	/* Release mutexes and reenable signals */
@@ -1025,6 +1073,8 @@ void ust_after_fork_parent(sigset_t *restore_sigset)
  */
 void ust_after_fork_child(sigset_t *restore_sigset)
 {
+	if (lttng_ust_nest_count)
+		return;
 	DBG("process %d", getpid());
 	/* Release urcu mutexes */
 	rcu_bp_after_fork_child();