static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
{
	struct task_struct *tsk;
	unsigned long *stack;
	struct vm_struct *stack_vm_area;
	int err;

	if (node == NUMA_NO_NODE)
		node = tsk_fork_get_node(orig);
	tsk = alloc_task_struct_node(node);
	if (!tsk)
		return NULL;

	stack = alloc_thread_stack_node(tsk, node);
	if (!stack)
		goto free_tsk;

	stack_vm_area = task_stack_vm_area(tsk);

	err = arch_dup_task_struct(tsk, orig);

	/*
	 * arch_dup_task_struct() clobbers the stack-related fields.  Make
	 * sure they're properly initialized before using any stack-related
	 * functions again.
	 */
	tsk->stack = stack;
#ifdef CONFIG_VMAP_STACK
	tsk->stack_vm_area = stack_vm_area;
#endif
#ifdef CONFIG_THREAD_INFO_IN_TASK
	atomic_set(&tsk->stack_refcount, 1);
#endif

	if (err)
		goto free_stack;

#ifdef CONFIG_SECCOMP
	/*
	 * We must handle setting up seccomp filters once we're under
	 * the sighand lock in case orig has changed between now and
	 * then. Until then, filter must be NULL to avoid messing up
	 * the usage counts on the error path calling free_task.
	 */
	tsk->seccomp.filter = NULL;
#endif

	setup_thread_stack(tsk, orig);
	clear_user_return_notifier(tsk);
	clear_tsk_need_resched(tsk);
	set_task_stack_end_magic(tsk);

#ifdef CONFIG_CC_STACKPROTECTOR
	tsk->stack_canary = get_random_canary();
#endif

	/*
	 * One for us, one for whoever does the "release_task()" (usually
	 * parent)
	 */
	atomic_set(&tsk->usage, 2);
#ifdef CONFIG_BLK_DEV_IO_TRACE
	tsk->btrace_seq = 0;
#endif
	tsk->splice_pipe = NULL;
	tsk->task_frag.page = NULL;
	tsk->wake_q.next = NULL;

	account_kernel_stack(tsk, 1);

	kcov_task_init(tsk);

#ifdef CONFIG_FAULT_INJECTION
	tsk->fail_nth = 0;
#endif

	return tsk;

free_stack:
	free_thread_stack(tsk);
free_tsk:
	free_task_struct(tsk);
	return NULL;
}
Unknown