X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=libust%2Ftracectl.c;h=0cff6fda9f035e8a009232268530e8e39e206ab4;hb=83aa16929ed1e60fabe1bda4824e7c4942ff42ec;hp=f720244530c9f60b77f5978875f712a5ea69658a;hpb=1d471d9fd21c9ef20cd7b0ea54a71168f0ad1b6e;p=ust.git

diff --git a/libust/tracectl.c b/libust/tracectl.c
index f720244..0cff6fd 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()
@@ -937,7 +957,7 @@ static void process_client_cmd(struct ustcomm_header *recv_header,
 		print_markers(fp);
 		fclose(fp);
 
-		reply_header->size = size;
+		reply_header->size = size + 1;	/* Include final \0 */
 
 		result = ustcomm_send(sock, reply_header, ptr);
 
@@ -963,7 +983,7 @@ static void process_client_cmd(struct ustcomm_header *recv_header,
 		print_trace_events(fp);
 		fclose(fp);
 
-		reply_header->size = size;
+		reply_header->size = size + 1;	/* Include final \0 */
 
 		result = ustcomm_send(sock, reply_header, ptr);
 
@@ -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 */
 		}
 	}
 
@@ -1578,9 +1601,6 @@ 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
@@ -1608,8 +1628,11 @@ static void ust_fork(void)
 		ltt_trace_destroy(trace->trace_name, 1);
 	}
 
-	/* Clean up the listener socket and epoll, keeping the scoket file */
-	ustcomm_del_named_sock(listen_sock, 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 */
@@ -1664,6 +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 */
@@ -1671,6 +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) {
@@ -1681,7 +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);
 }
 
@@ -1690,7 +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();
 }