X-Git-Url: http://git.lttng.org./?a=blobdiff_plain;f=liblttng-ust%2Flttng-ust-comm.c;h=44e8bab4c24ca4aa2a77b72727288c9b24c8e67d;hb=c022630241628bd0233d3369ca3e418717fde89d;hp=b968b498acc52874b3472544691bbaef05364d48;hpb=cd27263b5ddfee00e67674cae4fdf05b70a43438;p=lttng-ust.git

diff --git a/liblttng-ust/lttng-ust-comm.c b/liblttng-ust/lttng-ust-comm.c
index b968b498..44e8bab4 100644
--- a/liblttng-ust/lttng-ust-comm.c
+++ b/liblttng-ust/lttng-ust-comm.c
@@ -239,6 +239,7 @@ int handle_message(struct sock_info *sock_info,
 	const struct lttng_ust_objd_ops *ops;
 	struct ustcomm_ust_reply lur;
 	int shm_fd, wait_fd;
+	union ust_args args;
 
 	ust_lock();
 
@@ -271,7 +272,8 @@ int handle_message(struct sock_info *sock_info,
 	default:
 		if (ops->cmd)
 			ret = ops->cmd(lum->handle, lum->cmd,
-					(unsigned long) &lum->u);
+					(unsigned long) &lum->u,
+					&args);
 		else
 			ret = -ENOSYS;
 		break;
@@ -287,28 +289,30 @@ end:
 		//lur.ret_code = USTCOMM_SESSION_FAIL;
 		lur.ret_code = ret;
 	}
-	switch (lum->cmd) {
-	case LTTNG_UST_STREAM:
-		/*
-		 * Special-case reply to send stream info.
-		 * Use lum.u output.
-		 */
-		lur.u.stream.memory_map_size = lum->u.stream.memory_map_size;
-		shm_fd = lum->u.stream.shm_fd;
-		wait_fd = lum->u.stream.wait_fd;
-		break;
-	case LTTNG_UST_METADATA:
-	case LTTNG_UST_CHANNEL:
-		lur.u.channel.memory_map_size = lum->u.channel.memory_map_size;
-		shm_fd = lum->u.channel.shm_fd;
-		wait_fd = lum->u.channel.wait_fd;
-		break;
-	case LTTNG_UST_TRACER_VERSION:
-		lur.u.version = lum->u.version;
-		break;
-	case LTTNG_UST_TRACEPOINT_LIST_GET:
-		memcpy(&lur.u.tracepoint, &lum->u.tracepoint, sizeof(lur.u.tracepoint));
-		break;
+	if (ret >= 0) {
+		switch (lum->cmd) {
+		case LTTNG_UST_STREAM:
+			/*
+			 * Special-case reply to send stream info.
+			 * Use lum.u output.
+			 */
+			lur.u.stream.memory_map_size = *args.stream.memory_map_size;
+			shm_fd = *args.stream.shm_fd;
+			wait_fd = *args.stream.wait_fd;
+			break;
+		case LTTNG_UST_METADATA:
+		case LTTNG_UST_CHANNEL:
+			lur.u.channel.memory_map_size = *args.channel.memory_map_size;
+			shm_fd = *args.channel.shm_fd;
+			wait_fd = *args.channel.wait_fd;
+			break;
+		case LTTNG_UST_TRACER_VERSION:
+			lur.u.version = lum->u.version;
+			break;
+		case LTTNG_UST_TRACEPOINT_LIST_GET:
+			memcpy(&lur.u.tracepoint, &lum->u.tracepoint, sizeof(lur.u.tracepoint));
+			break;
+		}
 	}
 	ret = send_reply(sock, &lur);
 	if (ret < 0) {
@@ -336,13 +340,57 @@ end:
 			goto error;
 		}
 	}
+	/*
+	 * We still have the memory map reference, and the fds have been
+	 * sent to the sessiond. We can therefore close those fds. Note
+	 * that we keep the write side of the wait_fd open, but close
+	 * the read side.
+	 */
+	if (lur.ret_code == USTCOMM_OK) {
+		switch (lum->cmd) {
+		case LTTNG_UST_STREAM:
+			if (shm_fd >= 0) {
+				ret = close(shm_fd);
+				if (ret) {
+					PERROR("Error closing stream shm_fd");
+				}
+				*args.stream.shm_fd = -1;
+			}
+			if (wait_fd >= 0) {
+				ret = close(wait_fd);
+				if (ret) {
+					PERROR("Error closing stream wait_fd");
+				}
+				*args.stream.wait_fd = -1;
+			}
+			break;
+		case LTTNG_UST_METADATA:
+		case LTTNG_UST_CHANNEL:
+			if (shm_fd >= 0) {
+				ret = close(shm_fd);
+				if (ret) {
+					PERROR("Error closing channel shm_fd");
+				}
+				*args.channel.shm_fd = -1;
+			}
+			if (wait_fd >= 0) {
+				ret = close(wait_fd);
+				if (ret) {
+					PERROR("Error closing channel wait_fd");
+				}
+				*args.channel.wait_fd = -1;
+			}
+			break;
+		}
+	}
+
 error:
 	ust_unlock();
 	return ret;
 }
 
 static
-void cleanup_sock_info(struct sock_info *sock_info)
+void cleanup_sock_info(struct sock_info *sock_info, int exiting)
 {
 	int ret;
 
@@ -361,7 +409,13 @@ void cleanup_sock_info(struct sock_info *sock_info)
 		sock_info->root_handle = -1;
 	}
 	sock_info->constructor_sem_posted = 0;
-	if (sock_info->wait_shm_mmap) {
+	/*
+	 * wait_shm_mmap is used by listener threads outside of the
+	 * ust lock, so we cannot tear it down ourselves, because we
+	 * cannot join on these threads. Leave this task to the OS
+	 * process exit.
+	 */
+	if (!exiting && sock_info->wait_shm_mmap) {
 		ret = munmap(sock_info->wait_shm_mmap, sysconf(_SC_PAGE_SIZE));
 		if (ret) {
 			ERR("Error unmapping wait shm");
@@ -835,10 +889,17 @@ void __attribute__((constructor)) lttng_ust_init(void)
 static
 void lttng_ust_cleanup(int exiting)
 {
-	cleanup_sock_info(&global_apps);
+	cleanup_sock_info(&global_apps, exiting);
 	if (local_apps.allowed) {
-		cleanup_sock_info(&local_apps);
+		cleanup_sock_info(&local_apps, exiting);
 	}
+	/*
+	 * The teardown in this function all affect data structures
+	 * accessed under the UST lock by the listener thread. This
+	 * lock, along with the lttng_ust_comm_should_quit flag, ensure
+	 * that none of these threads are accessing this data at this
+	 * point.
+	 */
 	lttng_ust_abi_exit();
 	lttng_ust_events_exit();
 	ltt_ring_buffer_client_discard_exit();
@@ -872,6 +933,7 @@ void __attribute__((destructor)) lttng_ust_exit(void)
 	lttng_ust_comm_should_quit = 1;
 	ust_unlock();
 
+	/* cancel threads */
 	ret = pthread_cancel(global_apps.ust_listener);
 	if (ret) {
 		ERR("Error cancelling global ust listener thread");
@@ -882,6 +944,14 @@ void __attribute__((destructor)) lttng_ust_exit(void)
 			ERR("Error cancelling local ust listener thread");
 		}
 	}
+	/*
+	 * Do NOT join threads: use of sys_futex makes it impossible to
+	 * join the threads without using async-cancel, but async-cancel
+	 * is delivered by a signal, which could hit the target thread
+	 * anywhere in its code path, including while the ust_lock() is
+	 * held, causing a deadlock for the other thread. Let the OS
+	 * cleanup the threads if there are stalled in a syscall.
+	 */
 	lttng_ust_cleanup(1);
 }