/* * 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){	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_CLAIMED;		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 @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){	/* All work should have been flushed before going offline */	WARN_ON_ONCE(cpu_is_offline(cpu)); #ifdef CONFIG_SMP 	/* Arch remote IPI send/receive backend aren't NMI safe */	WARN_ON_ONCE(in_nmi()); 	/* Only queue if not already pending */	if (!irq_work_claim(work))		return false; 	if (llist_add(&work->llnode, &per_cpu(raised_list, cpu)))		arch_send_call_function_single_ipi(cpu); #else /* #ifdef CONFIG_SMP */	irq_work_queue(work);#endif /* #else #ifdef CONFIG_SMP */ 	return true;} /* 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(); 	/* If the work is "lazy", handle it from next tick if any */	if (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();	} 	preempt_enable(); 	return true;}EXPORT_SYMBOL_GPL(irq_work_queue); 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;} static void irq_work_run_list(struct llist_head *list){	struct irq_work *work, *tmp;	struct llist_node *llnode;	unsigned long flags; 	BUG_ON(!irqs_disabled()); 	if (llist_empty(list))		return; 	llnode = llist_del_all(list);	llist_for_each_entry_safe(work, tmp, llnode, 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);	}} /* * 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 (work->flags & IRQ_WORK_BUSY)		cpu_relax();}EXPORT_SYMBOL_GPL(irq_work_sync);