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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_int();#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);  return tsk; free_stack: free_thread_stack(tsk);free_tsk: free_task_struct(tsk); return NULL;} static struct kmem_cache *task_struct_cachep; static inline struct task_struct *alloc_task_struct_node(int node){ return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);} static inline void free_task_struct(struct task_struct *tsk){ kmem_cache_free(task_struct_cachep, tsk);}  

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