restore: sync threads

Use the save mechanosm as for processes.

* Threads should starts together with processes
* If a thread segfaulted, we should be able to detect it.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>

cr-restore.c

@@ -422,7 +422,7 @@ static int prepare_shared(int ps_fd)
 
 		task_add_pid(e.pid);
 
-		task_entries->nr++;
+		task_entries->nr += e.nr_threads;
 
 		lseek(ps_fd, e.nr_children * sizeof(u32) + e.nr_threads * sizeof(u32), SEEK_CUR);
 	}

restorer.c

@@ -196,6 +196,13 @@ long restore_thread(struct thread_restore_args *args)
 		 */
 
 		restore_creds(NULL);
+		cr_wait_dec(&task_entries->nr_in_progress);
+
+		write_num(sys_gettid());
+		write_string_n(": Restored");
+
+		cr_wait_while(&task_entries->start, CR_STATE_RESTORE);
+		cr_wait_dec(&task_entries->nr_in_progress);
 
 		new_sp = (long)rt_sigframe + 8;
 		asm volatile(