/* * Copyright (C) 2010 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com> * * 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 <asm/processor.h>  static DEFINE_PER_CPU(struct llist_head, irq_work_list);static DEFINE_PER_CPU(int, irq_work_raised); /* * Claim the entry so that no one else will poke at it. */static bool irq_work_claim(struct irq_work *work){	unsigned long flags, oflags, nflags; 	/*	 * Start with our best wish as a premise but only trust any	 * flag value after cmpxchg() result.	 */	flags = work->flags & ~IRQ_WORK_PENDING;	for (;;) {		nflags = flags | IRQ_WORK_FLAGS;		oflags = cmpxchg(&work->flags, flags, nflags);		if (oflags == flags)			break;		if (oflags & IRQ_WORK_PENDING)			return false;		flags = oflags;		cpu_relax();	} 	return true;} void __weak arch_irq_work_raise(void){	/*	 * Lame architectures will get the timer tick callback	 */} /* * Enqueue the irq_work @entry unless it's already pending * somewhere. * * Can be re-enqueued while the callback is still in progress. */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(); 	llist_add(&work->llnode, &__get_cpu_var(irq_work_list)); 	/*	 * If the work is not "lazy" or the tick is stopped, raise the irq	 * work interrupt (if supported by the arch), otherwise, just wait	 * for the next tick.	 */	if (!(work->flags & IRQ_WORK_LAZY) || tick_nohz_tick_stopped()) {		if (!this_cpu_cmpxchg(irq_work_raised, 0, 1))			arch_irq_work_raise();	} 	preempt_enable(); 	return true;}EXPORT_SYMBOL_GPL(irq_work_queue); bool irq_work_needs_cpu(void){	struct llist_head *this_list; 	this_list = &__get_cpu_var(irq_work_list);	if (llist_empty(this_list))		return false; 	/* All work should have been flushed before going offline */	WARN_ON_ONCE(cpu_is_offline(smp_processor_id())); 	return true;} static void __irq_work_run(void){	unsigned long flags;	struct irq_work *work;	struct llist_head *this_list;	struct llist_node *llnode;  	/*	 * Reset the "raised" state right before we check the list because	 * an NMI may enqueue after we find the list empty from the runner.	 */	__this_cpu_write(irq_work_raised, 0);	barrier(); 	this_list = &__get_cpu_var(irq_work_list);	if (llist_empty(this_list))		return; 	BUG_ON(!irqs_disabled()); 	llnode = llist_del_all(this_list);	while (llnode != NULL) {		work = llist_entry(llnode, struct irq_work, llnode); 		llnode = llist_next(llnode); 		/*		 * 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 = work->flags & ~IRQ_WORK_PENDING;		xchg(&work->flags, flags); 		work->func(work);		/*		 * Clear the BUSY bit and return to the free state if		 * no-one else claimed it meanwhile.		 */		(void)cmpxchg(&work->flags, flags, flags & ~IRQ_WORK_BUSY);	}} /* * Run the irq_work entries on this cpu. Requires to be ran from hardirq * context with local IRQs disabled. */void irq_work_run(void){	BUG_ON(!in_irq());	__irq_work_run();}EXPORT_SYMBOL_GPL(irq_work_run); /* * Synchronize against the irq_work @entry, ensures the entry is not * currently in use. */void irq_work_sync(struct irq_work *work){	WARN_ON_ONCE(irqs_disabled()); 	while (work->flags & IRQ_WORK_BUSY)		cpu_relax();}EXPORT_SYMBOL_GPL(irq_work_sync); #ifdef CONFIG_HOTPLUG_CPUstatic int irq_work_cpu_notify(struct notifier_block *self,			       unsigned long action, void *hcpu){	long cpu = (long)hcpu; 	switch (action) {	case CPU_DYING:		/* Called from stop_machine */		if (WARN_ON_ONCE(cpu != smp_processor_id()))			break;		__irq_work_run();		break;	default:		break;	}	return NOTIFY_OK;} static struct notifier_block cpu_notify; static __init int irq_work_init_cpu_notifier(void){	cpu_notify.notifier_call = irq_work_cpu_notify;	cpu_notify.priority = 0;	register_cpu_notifier(&cpu_notify);	return 0;}device_initcall(irq_work_init_cpu_notifier); #endif /* CONFIG_HOTPLUG_CPU */