// 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 <asm/processor.h>  static DEFINE_PER_CPU(struct llist_head, raised_list);static DEFINE_PER_CPU(struct llist_head, 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->flags);	/*	 * If the work is already pending, no need to raise the IPI.	 * The pairing atomic_fetch_andnot() in irq_work_run() 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){	/* If the work is "lazy", handle it from next tick if any */	if (atomic_read(&work->flags) & IRQ_WORK_LAZY) {		if (llist_add(&work->llnode, this_cpu_ptr(&lazy_list)) &&		    tick_nohz_tick_stopped())			arch_irq_work_raise();	} else {		if (llist_add(&work->llnode, this_cpu_ptr(&raised_list)))			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; 	preempt_disable();	if (cpu != smp_processor_id()) {		/* Arch remote IPI send/receive backend aren't NMI safe */		WARN_ON_ONCE(in_nmi());		__smp_call_single_queue(cpu, &work->llnode);	} else {		__irq_work_queue_local(work);	}	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.	 * Make it immediately visible so that other CPUs trying	 * to claim that work don't rely on us to handle their data	 * while we are in the middle of the func.	 */	flags = atomic_fetch_andnot(IRQ_WORK_PENDING, &work->flags); 	lockdep_irq_work_enter(work);	work->func(work);	lockdep_irq_work_exit(work);	/*	 * Clear the BUSY bit and return to the free state if	 * no-one else claimed it meanwhile.	 */	flags &= ~IRQ_WORK_PENDING;	(void)atomic_cmpxchg(&work->flags, flags, flags & ~IRQ_WORK_BUSY);} static void irq_work_run_list(struct llist_head *list){	struct irq_work *work, *tmp;	struct llist_node *llnode; 	BUG_ON(!irqs_disabled()); 	if (llist_empty(list))		return; 	llnode = llist_del_all(list);	llist_for_each_entry_safe(work, tmp, llnode, llnode)		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));	irq_work_run_list(this_cpu_ptr(&lazy_list));}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);	irq_work_run_list(this_cpu_ptr(&lazy_list));} /* * 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(); 	while (atomic_read(&work->flags) & IRQ_WORK_BUSY)		cpu_relax();}EXPORT_SYMBOL_GPL(irq_work_sync);