X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;f=liblttng-ust%2Flttng-ust-comm.c;h=67438117408715cff1e009123d392544dcb9bd96;hb=e63683c765cba41c0b140e283d2eb03523e4c57e;hp=5e738b06cf6eee5b539f4f507ba97817525a8fbf;hpb=e37047b693079a1136cc467f6ea9b8090ce58d10;p=lttng-ust.git

diff --git a/liblttng-ust/lttng-ust-comm.c b/liblttng-ust/lttng-ust-comm.c
index 5e738b06..67438117 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.
  */
@@ -130,6 +136,15 @@ extern void ltt_ring_buffer_client_overwrite_exit(void);
 extern void ltt_ring_buffer_client_discard_exit(void);
 extern void ltt_ring_buffer_metadata_client_exit(void);
 
+/*
+ * Force a read (imply TLS fixup for dlopen) of TLS variables.
+ */
+static
+void lttng_fixup_nest_count_tls(void)
+{
+	asm volatile ("" : : "m" (lttng_ust_nest_count));
+}
+
 static
 int setup_local_apps(void)
 {
@@ -469,7 +484,9 @@ 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;
 
@@ -838,6 +855,7 @@ void __attribute__((constructor)) lttng_ust_init(void)
 {
 	struct timespec constructor_timeout;
 	sigset_t sig_all_blocked, orig_parent_mask;
+	pthread_attr_t thread_attr;
 	int timeout_mode;
 	int ret;
 
@@ -852,6 +870,7 @@ void __attribute__((constructor)) lttng_ust_init(void)
 	lttng_fixup_event_tls();
 	lttng_fixup_ringbuffer_tls();
 	lttng_fixup_vtid_tls();
+	lttng_fixup_nest_count_tls();
 
 	/*
 	 * We want precise control over the order in which we construct
@@ -886,13 +905,22 @@ void __attribute__((constructor)) lttng_ust_init(void)
 		ERR("pthread_sigmask: %s", strerror(ret));
 	}
 
-	ret = pthread_create(&global_apps.ust_listener, NULL,
+	ret = pthread_attr_init(&thread_attr);
+	if (ret) {
+		ERR("pthread_attr_init: %s", strerror(ret));
+	}
+	ret = pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_DETACHED);
+	if (ret) {
+		ERR("pthread_attr_setdetachstate: %s", strerror(ret));
+	}
+
+	ret = pthread_create(&global_apps.ust_listener, &thread_attr,
 			ust_listener_thread, &global_apps);
 	if (ret) {
 		ERR("pthread_create global: %s", strerror(ret));
 	}
 	if (local_apps.allowed) {
-		ret = pthread_create(&local_apps.ust_listener, NULL,
+		ret = pthread_create(&local_apps.ust_listener, &thread_attr,
 				ust_listener_thread, &local_apps);
 		if (ret) {
 			ERR("pthread_create local: %s", strerror(ret));
@@ -900,6 +928,10 @@ void __attribute__((constructor)) lttng_ust_init(void)
 	} else {
 		handle_register_done(&local_apps);
 	}
+	ret = pthread_attr_destroy(&thread_attr);
+	if (ret) {
+		ERR("pthread_attr_destroy: %s", strerror(ret));
+	}
 
 	/* Restore original signal mask in parent */
 	ret = pthread_sigmask(SIG_SETMASK, &orig_parent_mask, NULL);
@@ -1019,6 +1051,8 @@ 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);
@@ -1044,6 +1078,8 @@ 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 */
@@ -1061,6 +1097,8 @@ 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();