Fix thread stack allocation

We need to allocate the stack before the thread starts running.

include/aos/threads.h

@@ -35,6 +35,8 @@ typedef int (*thread_func_t)(void *);
 struct thread *thread_create(thread_func_t start_func, void *data);
 struct thread *thread_create_varstack(thread_func_t start_func, void *arg,
                                       size_t stacksize);
+struct thread *thread_create_varstack_alloc(thread_func_t start_func, void *arg,
+                                            size_t stacksize);
 void thread_yield(void);
 void thread_yield_dispatcher(struct capref endpoint);
 void thread_exit(int status);
@@ -122,8 +124,6 @@ static inline void thread_once(thread_once_t *control, void (*func)(void)) {
  */
 void thread_set_status(int status);
 
-void thread_allocate_stack(struct thread *thread);
-
 __END_DECLS
 
 #endif  // LIBBARRELFISH_THREADS_H

lib/aos/threads.c

@@ -463,6 +463,28 @@ struct thread *thread_create(thread_func_t start_func, void *arg)
     return thread_create_varstack(start_func, arg, THREADS_DEFAULT_STACK_BYTES);
 }
 
+/**
+ * \brief Like thread_create_varstack, but allocate all pages of
+ * the thread stack before starting the thread.
+ */
+struct thread *thread_create_varstack_alloc(thread_func_t start_func, void *arg,
+                                      size_t stacksize)
+{
+    struct thread *newthread = thread_create_unrunnable(start_func, arg, stacksize);
+    if (newthread) {
+        for (volatile uint8_t *p = newthread->stack; (void*)p < newthread->stack_top; p += BASE_PAGE_SIZE) {
+            *p; // cause a page fault
+        }
+        // enqueue on runq
+        dispatcher_handle_t handle = disp_disable();
+        struct dispatcher_generic *disp_gen = get_dispatcher_generic(handle);
+        newthread->disp = handle;
+        thread_enqueue(newthread, &disp_gen->runq);
+        disp_enable(handle);
+    }
+    return newthread;
+}
+
 /**
  * \brief Wait for termination of another thread
  *
@@ -1462,13 +1484,3 @@ void thread_deliver_exception_disabled(dispatcher_handle_t handle,
 
     disp_resume(handle, &thread->regs);
 }
-
-/**
- * \brief Allocate all pages of the thread stack.
- */
-void thread_allocate_stack(struct thread *thread)
-{
-    for (volatile uint8_t *p = thread->stack; (void*)p < thread->stack_top; p += BASE_PAGE_SIZE) {
-        *p; // cause a page fault
-    }
-}

usr/init/main.c

@@ -247,11 +247,10 @@ app_main(int argc, char *argv[]) {
 
     ram_alloc_set(ram_alloc_remote_core);
 
-    struct thread *urpc_server_thread = thread_create(urpc_server, &urpc_to_app_server);
     // Allocate all pages of the thread stack now.
-    // We can't have page fault while the thread is running,
+    // We can't have page faults while the thread is running,
     // because URPC calls may only be done from the main thread.
-    thread_allocate_stack(urpc_server_thread);
+    thread_create_varstack_alloc(urpc_server, &urpc_to_app_server, THREADS_DEFAULT_STACK_BYTES);
 
 
     // TODO: Spawn system processes etc. here