#include <linux/spinlock.h>#include <linux/task_work.h>#include <linux/tracehook.h> inttask_work_add(struct task_struct *task, struct task_work *twork, bool notify){	unsigned long flags;	int err = -ESRCH; #ifndef TIF_NOTIFY_RESUME	if (notify)		return -ENOTSUPP;#endif	/*	 * We must not insert the new work if the task has already passed	 * exit_task_work(). We rely on do_exit()->raw_spin_unlock_wait()	 * and check PF_EXITING under pi_lock.	 */	raw_spin_lock_irqsave(&task->pi_lock, flags);	if (likely(!(task->flags & PF_EXITING))) {		hlist_add_head(&twork->hlist, &task->task_works);		err = 0;	}	raw_spin_unlock_irqrestore(&task->pi_lock, flags); 	/* test_and_set_bit() implies mb(), see tracehook_notify_resume(). */	if (likely(!err) && notify)		set_notify_resume(task);	return err;} struct task_work *task_work_cancel(struct task_struct *task, task_work_func_t func){	unsigned long flags;	struct task_work *twork;	struct hlist_node *pos; 	raw_spin_lock_irqsave(&task->pi_lock, flags);	hlist_for_each_entry(twork, pos, &task->task_works, hlist) {		if (twork->func == func) {			hlist_del(&twork->hlist);			goto found;		}	}	twork = NULL; found:	raw_spin_unlock_irqrestore(&task->pi_lock, flags); 	return twork;} void task_work_run(void){	struct task_struct *task = current;	struct hlist_head task_works;	struct hlist_node *pos; 	raw_spin_lock_irq(&task->pi_lock);	hlist_move_list(&task->task_works, &task_works);	raw_spin_unlock_irq(&task->pi_lock); 	if (unlikely(hlist_empty(&task_works)))		return;	/*	 * We use hlist to save the space in task_struct, but we want fifo.	 * Find the last entry, the list should be short, then process them	 * in reverse order.	 */	for (pos = task_works.first; pos->next; pos = pos->next)		; 	for (;;) {		struct hlist_node **pprev = pos->pprev;		struct task_work *twork = container_of(pos, struct task_work,							hlist);		twork->func(twork); 		if (pprev == &task_works.first)			break;		pos = container_of(pprev, struct hlist_node, next);	}}