// SPDX-License-Identifier: GPL-2.0#include <linux/irq_work.h>#include <linux/spinlock.h>#include <linux/task_work.h>#include <linux/resume_user_mode.h> static struct callback_head work_exited; /* all we need is ->next == NULL */ static void task_work_set_notify_irq(struct irq_work *entry){	test_and_set_tsk_thread_flag(current, TIF_NOTIFY_RESUME);}static DEFINE_PER_CPU(struct irq_work, irq_work_NMI_resume) =	IRQ_WORK_INIT_HARD(task_work_set_notify_irq); /** * task_work_add - ask the @task to execute @work->func() * @task: the task which should run the callback * @work: the callback to run * @notify: how to notify the targeted task * * Queue @work for task_work_run() below and notify the @task if @notify * is @TWA_RESUME, @TWA_SIGNAL, @TWA_SIGNAL_NO_IPI or @TWA_NMI_CURRENT. * * @TWA_SIGNAL works like signals, in that the it will interrupt the targeted * task and run the task_work, regardless of whether the task is currently * running in the kernel or userspace. * @TWA_SIGNAL_NO_IPI works like @TWA_SIGNAL, except it doesn't send a * reschedule IPI to force the targeted task to reschedule and run task_work. * This can be advantageous if there's no strict requirement that the * task_work be run as soon as possible, just whenever the task enters the * kernel anyway. * @TWA_RESUME work is run only when the task exits the kernel and returns to * user mode, or before entering guest mode. * @TWA_NMI_CURRENT works like @TWA_RESUME, except it can only be used for the * current @task and if the current context is NMI. * * Fails if the @task is exiting/exited and thus it can't process this @work. * Otherwise @work->func() will be called when the @task goes through one of * the aforementioned transitions, or exits. * * If the targeted task is exiting, then an error is returned and the work item * is not queued. It's up to the caller to arrange for an alternative mechanism * in that case. * * Note: there is no ordering guarantee on works queued here. The task_work * list is LIFO. * * RETURNS: * 0 if succeeds or -ESRCH. */int task_work_add(struct task_struct *task, struct callback_head *work,		  enum task_work_notify_mode notify){	struct callback_head *head; 	if (notify == TWA_NMI_CURRENT) {		if (WARN_ON_ONCE(task != current))			return -EINVAL;	} else {		/* record the work call stack in order to print it in KASAN reports */		kasan_record_aux_stack(work);	} 	head = READ_ONCE(task->task_works);	do {		if (unlikely(head == &work_exited))			return -ESRCH;		work->next = head;	} while (!try_cmpxchg(&task->task_works, &head, work)); 	switch (notify) {	case TWA_NONE:		break;	case TWA_RESUME:		set_notify_resume(task);		break;	case TWA_SIGNAL:		set_notify_signal(task);		break;	case TWA_SIGNAL_NO_IPI:		__set_notify_signal(task);		break;	case TWA_NMI_CURRENT:		irq_work_queue(this_cpu_ptr(&irq_work_NMI_resume));		break;	default:		WARN_ON_ONCE(1);		break;	} 	return 0;} /** * task_work_cancel_match - cancel a pending work added by task_work_add() * @task: the task which should execute the work * @match: match function to call * @data: data to be passed in to match function * * RETURNS: * The found work or NULL if not found. */struct callback_head *task_work_cancel_match(struct task_struct *task,		       bool (*match)(struct callback_head *, void *data),		       void *data){	struct callback_head **pprev = &task->task_works;	struct callback_head *work;	unsigned long flags; 	if (likely(!task_work_pending(task)))		return NULL;	/*	 * If cmpxchg() fails we continue without updating pprev.	 * Either we raced with task_work_add() which added the	 * new entry before this work, we will find it again. Or	 * we raced with task_work_run(), *pprev == NULL/exited.	 */	raw_spin_lock_irqsave(&task->pi_lock, flags);	work = READ_ONCE(*pprev);	while (work) {		if (!match(work, data)) {			pprev = &work->next;			work = READ_ONCE(*pprev);		} else if (try_cmpxchg(pprev, &work, work->next))			break;	}	raw_spin_unlock_irqrestore(&task->pi_lock, flags); 	return work;} static bool task_work_func_match(struct callback_head *cb, void *data){	return cb->func == data;} /** * task_work_cancel_func - cancel a pending work matching a function added by task_work_add() * @task: the task which should execute the func's work * @func: identifies the func to match with a work to remove * * Find the last queued pending work with ->func == @func and remove * it from queue. * * RETURNS: * The found work or NULL if not found. */struct callback_head *task_work_cancel_func(struct task_struct *task, task_work_func_t func){	return task_work_cancel_match(task, task_work_func_match, func);} static bool task_work_match(struct callback_head *cb, void *data){	return cb == data;} /** * task_work_cancel - cancel a pending work added by task_work_add() * @task: the task which should execute the work * @cb: the callback to remove if queued * * Remove a callback from a task's queue if queued. * * RETURNS: * True if the callback was queued and got cancelled, false otherwise. */bool task_work_cancel(struct task_struct *task, struct callback_head *cb){	struct callback_head *ret; 	ret = task_work_cancel_match(task, task_work_match, cb); 	return ret == cb;} /** * task_work_run - execute the works added by task_work_add() * * Flush the pending works. Should be used by the core kernel code. * Called before the task returns to the user-mode or stops, or when * it exits. In the latter case task_work_add() can no longer add the * new work after task_work_run() returns. */void task_work_run(void){	struct task_struct *task = current;	struct callback_head *work, *head, *next; 	for (;;) {		/*		 * work->func() can do task_work_add(), do not set		 * work_exited unless the list is empty.		 */		work = READ_ONCE(task->task_works);		do {			head = NULL;			if (!work) {				if (task->flags & PF_EXITING)					head = &work_exited;				else					break;			}		} while (!try_cmpxchg(&task->task_works, &work, head)); 		if (!work)			break;		/*		 * Synchronize with task_work_cancel_match(). It can not remove		 * the first entry == work, cmpxchg(task_works) must fail.		 * But it can remove another entry from the ->next list.		 */		raw_spin_lock_irq(&task->pi_lock);		raw_spin_unlock_irq(&task->pi_lock); 		do {			next = work->next;			work->func(work);			work = next;			cond_resched();		} while (work);	}}