/* * 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 <asm/processor.h> /* * An entry can be in one of four states: * * free	     NULL, 0 -> {claimed}       : free to be used * claimed   NULL, 3 -> {pending}       : claimed to be enqueued * pending   next, 3 -> {busy}          : queued, pending callback * busy      NULL, 2 -> {free, claimed} : callback in progress, can be claimed */ #define IRQ_WORK_PENDING	1UL#define IRQ_WORK_BUSY		2UL#define IRQ_WORK_FLAGS		3UL static DEFINE_PER_CPU(struct llist_head, irq_work_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, nflags; 	for (;;) {		flags = work->flags;		if (flags & IRQ_WORK_PENDING)			return false;		nflags = flags | IRQ_WORK_FLAGS;		if (cmpxchg(&work->flags, flags, nflags) == flags)			break;		cpu_relax();	} 	return true;} void __weak arch_irq_work_raise(void){	/*	 * Lame architectures will get the timer tick callback	 */} /* * Queue the entry and raise the IPI if needed. */static void __irq_work_queue(struct irq_work *work){	bool empty; 	preempt_disable(); 	empty = llist_add(&work->llnode, &__get_cpu_var(irq_work_list));	/* The list was empty, raise self-interrupt to start processing. */	if (empty)		arch_irq_work_raise(); 	preempt_enable();} /* * Enqueue the irq_work @entry, returns true on success, failure when the * @entry was already enqueued by someone else. * * Can be re-enqueued while the callback is still in progress. */bool irq_work_queue(struct irq_work *work){	if (!irq_work_claim(work)) {		/*		 * Already enqueued, can't do!		 */		return false;	} 	__irq_work_queue(work);	return true;}EXPORT_SYMBOL_GPL(irq_work_queue); /* * Run the irq_work entries on this cpu. Requires to be ran from hardirq * context with local IRQs disabled. */void irq_work_run(void){	struct irq_work *work;	struct llist_head *this_list;	struct llist_node *llnode; 	this_list = &__get_cpu_var(irq_work_list);	if (llist_empty(this_list))		return; 	BUG_ON(!in_irq());	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.		 */		work->flags = IRQ_WORK_BUSY;		work->func(work);		/*		 * Clear the BUSY bit and return to the free state if		 * no-one else claimed it meanwhile.		 */		(void)cmpxchg(&work->flags, IRQ_WORK_BUSY, 0);	}}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);