X-Git-Url: https://git.liburcu.org/?a=blobdiff_plain;f=libust%2Ftracectl.c;h=b058cb3ce19d0d317790ddbf03103164508d1eb4;hb=e625e9191bcb16522072aa34301cc517392f85ba;hp=d32deba978ac8d2500fa6a222d07a520a2db2ebc;hpb=fc1caebc8a71283c7766549ebed47300d1b52945;p=ust.git

diff --git a/libust/tracectl.c b/libust/tracectl.c
index d32deba..b058cb3 100644
--- a/libust/tracectl.c
+++ b/libust/tracectl.c
@@ -63,6 +63,16 @@ static char receive_buffer[USTCOMM_BUFFER_SIZE];
 static char send_buffer[USTCOMM_BUFFER_SIZE];
 
 static int epoll_fd;
+
+/*
+ * Listener thread data vs fork() protection mechanism. Ensures that no listener
+ * thread mutexes and data structures are being concurrently modified or held by
+ * other threads when fork() is executed.
+ */
+static pthread_mutex_t listener_thread_data_mutex = PTHREAD_MUTEX_INITIALIZER;
+
+/* Mutex protecting listen_sock. Nests inside listener_thread_data_mutex. */
+static pthread_mutex_t listen_sock_mutex = PTHREAD_MUTEX_INITIALIZER;
 static struct ustcomm_sock *listen_sock;
 
 extern struct chan_info_struct chan_infos[];
@@ -533,9 +543,19 @@ unlock_traces:
 	return retval;
 }
 
+static void release_listener_mutex(void *ptr)
+{
+	pthread_mutex_unlock(&listener_thread_data_mutex);
+}
+
 static void listener_cleanup(void *ptr)
 {
-	ustcomm_del_named_sock(listen_sock, 0);
+	pthread_mutex_lock(&listen_sock_mutex);
+	if (listen_sock) {
+		ustcomm_del_named_sock(listen_sock, 0);
+		listen_sock = NULL;
+	}
+	pthread_mutex_unlock(&listen_sock_mutex);
 }
 
 static void force_subbuf_switch()
@@ -1080,6 +1100,8 @@ void *listener_main(void *p)
 		}
 
 		for (i = 0; i < nfds; i++) {
+			pthread_mutex_lock(&listener_thread_data_mutex);
+			pthread_cleanup_push(release_listener_mutex, NULL);
 			epoll_sock = (struct ustcomm_sock *)events[i].data.ptr;
 			if (epoll_sock == listen_sock) {
 				addr_size = sizeof(struct sockaddr);
@@ -1108,6 +1130,7 @@ void *listener_main(void *p)
 							   epoll_sock->fd);
 				}
 			}
+			pthread_cleanup_pop(1);	/* release listener mutex */
 		}
 	}
 
@@ -1569,6 +1592,7 @@ static void ust_fork(void)
 {
 	struct ust_buffer *buf, *buf_tmp;
 	struct ustcomm_sock *sock, *sock_tmp;
+	struct ust_trace *trace, *trace_tmp;
 	int result;
 
 	/* FIXME: technically, the locks could have been taken before the fork */
@@ -1577,11 +1601,14 @@ static void ust_fork(void)
 	/* Get the pid of the new process */
 	processpid = getpid();
 
-	/* break lock if necessary */
-	ltt_unlock_traces();
+	/*
+	 * FIXME: This could be prettier, we loop over the list twice and
+	 * following good locking practice should lock around the loop
+	 */
+	cds_list_for_each_entry_safe(trace, trace_tmp, &ltt_traces.head, list) {
+		ltt_trace_stop(trace->trace_name);
+	}
 
-	ltt_trace_stop("auto");
-	ltt_trace_destroy("auto", 1);
 	/* Delete all active connections, but leave them in the epoll set */
 	cds_list_for_each_entry_safe(sock, sock_tmp, &ust_socks, list) {
 		ustcomm_del_sock(sock, 1);
@@ -1590,19 +1617,22 @@ static void ust_fork(void)
 	/* Delete all blocked consumers */
 	cds_list_for_each_entry_safe(buf, buf_tmp, &open_buffers_list,
 				 open_buffers_list) {
-		result = close(buf->data_ready_fd_read);
-		if (result == -1) {
-			PERROR("close");
-		}
-		result = close(buf->data_ready_fd_write);
-		if (result == -1) {
-			PERROR("close");
-		}
 		cds_list_del(&buf->open_buffers_list);
 	}
 
-	/* Clean up the listener socket and epoll, keeping the scoket file */
-	ustcomm_del_named_sock(listen_sock, 1);
+	/*
+	 * FIXME: This could be prettier, we loop over the list twice and
+	 * following good locking practice should lock around the loop
+	 */
+	cds_list_for_each_entry_safe(trace, trace_tmp, &ltt_traces.head, list) {
+		ltt_trace_destroy(trace->trace_name, 1);
+	}
+
+	/* Clean up the listener socket and epoll, keeping the socket file */
+	if (listen_sock) {
+		ustcomm_del_named_sock(listen_sock, 1);
+		listen_sock = NULL;
+	}
 	close(epoll_fd);
 
 	/* Re-start the launch sequence */
@@ -1657,6 +1687,16 @@ void ust_before_fork(ust_fork_info_t *fork_info)
                 PERROR("sigprocmask");
                 return;
         }
+
+	/*
+	 * Take the fork lock to make sure we are not in the middle of
+	 * something in the listener thread.
+	 */
+	pthread_mutex_lock(&listener_thread_data_mutex);
+	/*
+	 * Hold listen_sock_mutex to protect from listen_sock teardown.
+	 */
+	pthread_mutex_lock(&listen_sock_mutex);
 }
 
 /* Don't call this function directly in a traced program */
@@ -1664,6 +1704,9 @@ static void ust_after_fork_common(ust_fork_info_t *fork_info)
 {
 	int result;
 
+	pthread_mutex_unlock(&listen_sock_mutex);
+	pthread_mutex_unlock(&listener_thread_data_mutex);
+
         /* Restore signals */
         result = sigprocmask(SIG_SETMASK, &fork_info->orig_sigs, NULL);
         if (result == -1) {
@@ -1674,7 +1717,7 @@ static void ust_after_fork_common(ust_fork_info_t *fork_info)
 
 void ust_after_fork_parent(ust_fork_info_t *fork_info)
 {
-	/* Reenable signals */
+	/* Release mutexes and reenable signals */
 	ust_after_fork_common(fork_info);
 }
 
@@ -1683,7 +1726,15 @@ void ust_after_fork_child(ust_fork_info_t *fork_info)
 	/* First sanitize the child */
 	ust_fork();
 
-	/* Then reenable interrupts */
+	/* Then release mutexes and reenable signals */
 	ust_after_fork_common(fork_info);
+
+	/*
+	 * Make sure we clean up the urcu-bp thread list in the child by running
+	 * the garbage collection before any pthread_create can be called.
+	 * Failure to do so could lead to a deadlock caused by reuse of a thread
+	 * ID before urcu-bp garbage collection is performed.
+	 */
+	synchronize_rcu();
 }