Fix: don't cancel already exited threads

Ensure we don't issue pthread_cancel() on already exited threads.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/liblttng-ust/lttng-ust-comm.c b/liblttng-ust/lttng-ust-comm.c
index 5875693164229fe73d1db9f734c2c9a26356eb36..d7214370821d05b459a49a188b69734ab58139b7 100644 (file)
--- a/liblttng-ust/lttng-ust-comm.c
+++ b/liblttng-ust/lttng-ust-comm.c
@@ -96,6 +96,7 @@ struct sock_info {
        int constructor_sem_posted;
        int allowed;
        int global;
+       int thread_active;
 
        char sock_path[PATH_MAX];
        int socket;
@@ -111,6 +112,7 @@ struct sock_info global_apps = {
 
        .root_handle = -1,
        .allowed = 1,
+       .thread_active = 0,
 
        .sock_path = DEFAULT_GLOBAL_APPS_UNIX_SOCK,
        .socket = -1,
@@ -125,6 +127,7 @@ struct sock_info local_apps = {
        .global = 0,
        .root_handle = -1,
        .allowed = 0,   /* Check setuid bit first */
+       .thread_active = 0,
 
        .socket = -1,
 };
@@ -816,7 +819,6 @@ restart:
        ust_lock();
 
        if (lttng_ust_comm_should_quit) {
-               ust_unlock();
                goto quit;
        }
 
@@ -854,7 +856,6 @@ restart:
                ret = lttng_abi_create_root_handle();
                if (ret < 0) {
                        ERR("Error creating root handle");
-                       ust_unlock();
                        goto quit;
                }
                sock_info->root_handle = ret;
@@ -885,7 +886,6 @@ restart:
                        DBG("%s lttng-sessiond has performed an orderly shutdown", sock_info->name);
                        ust_lock();
                        if (lttng_ust_comm_should_quit) {
-                               ust_unlock();
                                goto quit;
                        }
                        /*
@@ -926,14 +926,16 @@ restart:
 end:
        ust_lock();
        if (lttng_ust_comm_should_quit) {
-               ust_unlock();
                goto quit;
        }
        /* Cleanup socket handles before trying to reconnect */
        lttng_ust_objd_table_owner_cleanup(sock_info);
        ust_unlock();
        goto restart;   /* try to reconnect */
+
 quit:
+       sock_info->thread_active = 0;
+       ust_unlock();
        return NULL;
 }
 
@@ -1045,17 +1047,24 @@ void __attribute__((constructor)) lttng_ust_init(void)
                ERR("pthread_attr_setdetachstate: %s", strerror(ret));
        }
 
+       ust_lock();
        ret = pthread_create(&global_apps.ust_listener, &thread_attr,
                        ust_listener_thread, &global_apps);
        if (ret) {
                ERR("pthread_create global: %s", strerror(ret));
        }
+       global_apps.thread_active = 1;
+       ust_unlock();
+
        if (local_apps.allowed) {
+               ust_lock();
                ret = pthread_create(&local_apps.ust_listener, &thread_attr,
                                ust_listener_thread, &local_apps);
                if (ret) {
                        ERR("pthread_create local: %s", strerror(ret));
                }
+               local_apps.thread_active = 1;
+               ust_unlock();
        } else {
                handle_register_done(&local_apps);
        }
@@ -1138,21 +1147,28 @@ void __attribute__((destructor)) lttng_ust_exit(void)
         */
        ust_lock();
        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: %s",
-                       strerror(ret));
+       if (global_apps.thread_active) {
+               ret = pthread_cancel(global_apps.ust_listener);
+               if (ret) {
+                       ERR("Error cancelling global ust listener thread: %s",
+                               strerror(ret));
+               } else {
+                       global_apps.thread_active = 0;
+               }
        }
-       if (local_apps.allowed) {
+       if (local_apps.thread_active) {
                ret = pthread_cancel(local_apps.ust_listener);
                if (ret) {
                        ERR("Error cancelling local ust listener thread: %s",
                                strerror(ret));
+               } else {
+                       local_apps.thread_active = 0;
                }
        }
+       ust_unlock();
+
        /*
         * Do NOT join threads: use of sys_futex makes it impossible to
         * join the threads without using async-cancel, but async-cancel