// SPDX-License-Identifier: GPL-2.0-only/* * Copyright (C) 2010 Red Hat, Inc., Peter Zijlstra * * Provides a framework for enqueueing and running callbacks from hardirq * context. The enqueueing is NMI-safe. */ #include <linux/bug.h>#include <linux/kernel.h>#include <linux/export.h>#include <linux/irq_work.h>#include <linux/percpu.h>#include <linux/hardirq.h>#include <linux/irqflags.h>#include <linux/sched.h>#include <linux/tick.h>#include <linux/cpu.h>#include <linux/notifier.h>#include <linux/smp.h>#include <linux/smpboot.h>#include <asm/processor.h>#include <linux/kasan.h> static DEFINE_PER_CPU(struct llist_head, raised_list);static DEFINE_PER_CPU(struct llist_head, lazy_list);static DEFINE_PER_CPU(struct task_struct *, irq_workd); static void wake_irq_workd(void){	struct task_struct *tsk = __this_cpu_read(irq_workd); 	if (!llist_empty(this_cpu_ptr(&lazy_list)) && tsk)		wake_up_process(tsk);} #ifdef CONFIG_SMPstatic void irq_work_wake(struct irq_work *entry){	wake_irq_workd();} static DEFINE_PER_CPU(struct irq_work, irq_work_wakeup) =	IRQ_WORK_INIT_HARD(irq_work_wake);#endif static int irq_workd_should_run(unsigned int cpu){	return !llist_empty(this_cpu_ptr(&lazy_list));} /* * Claim the entry so that no one else will poke at it. */static bool irq_work_claim(struct irq_work *work){	int oflags; 	oflags = atomic_fetch_or(IRQ_WORK_CLAIMED | CSD_TYPE_IRQ_WORK, &work->node.a_flags);	/*	 * If the work is already pending, no need to raise the IPI.	 * The pairing smp_mb() in irq_work_single() makes sure	 * everything we did before is visible.	 */	if (oflags & IRQ_WORK_PENDING)		return false;	return true;} void __weak arch_irq_work_raise(void){	/*	 * Lame architectures will get the timer tick callback	 */} /* Enqueue on current CPU, work must already be claimed and preempt disabled */static void __irq_work_queue_local(struct irq_work *work){	struct llist_head *list;	bool rt_lazy_work = false;	bool lazy_work = false;	int work_flags; 	work_flags = atomic_read(&work->node.a_flags);	if (work_flags & IRQ_WORK_LAZY)		lazy_work = true;	else if (IS_ENABLED(CONFIG_PREEMPT_RT) &&		 !(work_flags & IRQ_WORK_HARD_IRQ))		rt_lazy_work = true; 	if (lazy_work || rt_lazy_work)		list = this_cpu_ptr(&lazy_list);	else		list = this_cpu_ptr(&raised_list); 	if (!llist_add(&work->node.llist, list))		return; 	/* If the work is "lazy", handle it from next tick if any */	if (!lazy_work || tick_nohz_tick_stopped())		arch_irq_work_raise();} /* Enqueue the irq work @work on the current CPU */bool irq_work_queue(struct irq_work *work){	/* Only queue if not already pending */	if (!irq_work_claim(work))		return false; 	/* Queue the entry and raise the IPI if needed. */	preempt_disable();	__irq_work_queue_local(work);	preempt_enable(); 	return true;}EXPORT_SYMBOL_GPL(irq_work_queue); /* * Enqueue the irq_work @work on @cpu unless it's already pending * somewhere. * * Can be re-enqueued while the callback is still in progress. */bool irq_work_queue_on(struct irq_work *work, int cpu){#ifndef CONFIG_SMP	return irq_work_queue(work); #else /* CONFIG_SMP: */	/* All work should have been flushed before going offline */	WARN_ON_ONCE(cpu_is_offline(cpu)); 	/* Only queue if not already pending */	if (!irq_work_claim(work))		return false; 	kasan_record_aux_stack_noalloc(work); 	preempt_disable();	if (cpu != smp_processor_id()) {		/* Arch remote IPI send/receive backend aren't NMI safe */		WARN_ON_ONCE(in_nmi()); 		/*		 * On PREEMPT_RT the items which are not marked as		 * IRQ_WORK_HARD_IRQ are added to the lazy list and a HARD work		 * item is used on the remote CPU to wake the thread.		 */		if (IS_ENABLED(CONFIG_PREEMPT_RT) &&		    !(atomic_read(&work->node.a_flags) & IRQ_WORK_HARD_IRQ)) { 			if (!llist_add(&work->node.llist, &per_cpu(lazy_list, cpu)))				goto out; 			work = &per_cpu(irq_work_wakeup, cpu);			if (!irq_work_claim(work))				goto out;		} 		__smp_call_single_queue(cpu, &work->node.llist);	} else {		__irq_work_queue_local(work);	}out:	preempt_enable(); 	return true;#endif /* CONFIG_SMP */} bool irq_work_needs_cpu(void){	struct llist_head *raised, *lazy; 	raised = this_cpu_ptr(&raised_list);	lazy = this_cpu_ptr(&lazy_list); 	if (llist_empty(raised) || arch_irq_work_has_interrupt())		if (llist_empty(lazy))			return false; 	/* All work should have been flushed before going offline */	WARN_ON_ONCE(cpu_is_offline(smp_processor_id())); 	return true;} void irq_work_single(void *arg){	struct irq_work *work = arg;	int flags; 	/*	 * Clear the PENDING bit, after this point the @work can be re-used.	 * The PENDING bit acts as a lock, and we own it, so we can clear it	 * without atomic ops.	 */	flags = atomic_read(&work->node.a_flags);	flags &= ~IRQ_WORK_PENDING;	atomic_set(&work->node.a_flags, flags); 	/*	 * See irq_work_claim().	 */	smp_mb(); 	lockdep_irq_work_enter(flags);	work->func(work);	lockdep_irq_work_exit(flags); 	/*	 * Clear the BUSY bit, if set, and return to the free state if no-one	 * else claimed it meanwhile.	 */	(void)atomic_cmpxchg(&work->node.a_flags, flags, flags & ~IRQ_WORK_BUSY); 	if ((IS_ENABLED(CONFIG_PREEMPT_RT) && !irq_work_is_hard(work)) ||	    !arch_irq_work_has_interrupt())		rcuwait_wake_up(&work->irqwait);} static void irq_work_run_list(struct llist_head *list){	struct irq_work *work, *tmp;	struct llist_node *llnode; 	/*	 * On PREEMPT_RT IRQ-work which is not marked as HARD will be processed	 * in a per-CPU thread in preemptible context. Only the items which are	 * marked as IRQ_WORK_HARD_IRQ will be processed in hardirq context.	 */	BUG_ON(!irqs_disabled() && !IS_ENABLED(CONFIG_PREEMPT_RT)); 	if (llist_empty(list))		return; 	llnode = llist_del_all(list);	llist_for_each_entry_safe(work, tmp, llnode, node.llist)		irq_work_single(work);} /* * hotplug calls this through: *  hotplug_cfd() -> flush_smp_call_function_queue() */void irq_work_run(void){	irq_work_run_list(this_cpu_ptr(&raised_list));	if (!IS_ENABLED(CONFIG_PREEMPT_RT))		irq_work_run_list(this_cpu_ptr(&lazy_list));	else		wake_irq_workd();}EXPORT_SYMBOL_GPL(irq_work_run); void irq_work_tick(void){	struct llist_head *raised = this_cpu_ptr(&raised_list); 	if (!llist_empty(raised) && !arch_irq_work_has_interrupt())		irq_work_run_list(raised); 	if (!IS_ENABLED(CONFIG_PREEMPT_RT))		irq_work_run_list(this_cpu_ptr(&lazy_list));	else		wake_irq_workd();} /* * Synchronize against the irq_work @entry, ensures the entry is not * currently in use. */void irq_work_sync(struct irq_work *work){	lockdep_assert_irqs_enabled();	might_sleep(); 	if ((IS_ENABLED(CONFIG_PREEMPT_RT) && !irq_work_is_hard(work)) ||	    !arch_irq_work_has_interrupt()) {		rcuwait_wait_event(&work->irqwait, !irq_work_is_busy(work),				   TASK_UNINTERRUPTIBLE);		return;	} 	while (irq_work_is_busy(work))		cpu_relax();}EXPORT_SYMBOL_GPL(irq_work_sync); static void run_irq_workd(unsigned int cpu){	irq_work_run_list(this_cpu_ptr(&lazy_list));} static void irq_workd_setup(unsigned int cpu){	sched_set_fifo_low(current);} static struct smp_hotplug_thread irqwork_threads = {	.store                  = &irq_workd,	.setup			= irq_workd_setup,	.thread_should_run      = irq_workd_should_run,	.thread_fn              = run_irq_workd,	.thread_comm            = "irq_work/%u",}; static __init int irq_work_init_threads(void){	if (IS_ENABLED(CONFIG_PREEMPT_RT))		BUG_ON(smpboot_register_percpu_thread(&irqwork_threads));	return 0;}early_initcall(irq_work_init_threads);