/* * linux/kernel/workqueue.c * * Generic mechanism for defining kernel helper threads for running * arbitrary tasks in process context. * * Started by Ingo Molnar, Copyright (C) 2002 * * Derived from the taskqueue/keventd code by: * *   David Woodhouse <dwmw2@infradead.org> *   Andrew Morton <andrewm@uow.edu.au> *   Kai Petzke <wpp@marie.physik.tu-berlin.de> *   Theodore Ts'o <tytso@mit.edu> * * Made to use alloc_percpu by Christoph Lameter <clameter@sgi.com>. */ #include <linux/module.h>#include <linux/kernel.h>#include <linux/sched.h>#include <linux/init.h>#include <linux/signal.h>#include <linux/completion.h>#include <linux/workqueue.h>#include <linux/slab.h>#include <linux/cpu.h>#include <linux/notifier.h>#include <linux/kthread.h>#include <linux/hardirq.h>#include <linux/mempolicy.h>#include <linux/freezer.h>#include <linux/kallsyms.h>#include <linux/debug_locks.h>#include <linux/lockdep.h> /* * The per-CPU workqueue (if single thread, we always use the first * possible cpu). */struct cpu_workqueue_struct { 	spinlock_t lock; 	struct list_head worklist;	wait_queue_head_t more_work;	struct work_struct *current_work; 	struct workqueue_struct *wq;	struct task_struct *thread; 	int run_depth;		/* Detect run_workqueue() recursion depth */} ____cacheline_aligned; /* * The externally visible workqueue abstraction is an array of * per-CPU workqueues: */struct workqueue_struct {	struct cpu_workqueue_struct *cpu_wq;	struct list_head list;	const char *name;	int singlethread;	int freezeable;		/* Freeze threads during suspend */#ifdef CONFIG_LOCKDEP	struct lockdep_map lockdep_map;#endif}; /* Serializes the accesses to the list of workqueues. */static DEFINE_SPINLOCK(workqueue_lock);static LIST_HEAD(workqueues); static int singlethread_cpu __read_mostly;static cpumask_t cpu_singlethread_map __read_mostly;/* * _cpu_down() first removes CPU from cpu_online_map, then CPU_DEAD * flushes cwq->worklist. This means that flush_workqueue/wait_on_work * which comes in between can't use for_each_online_cpu(). We could * use cpu_possible_map, the cpumask below is more a documentation * than optimization. */static cpumask_t cpu_populated_map __read_mostly; /* If it's single threaded, it isn't in the list of workqueues. */static inline int is_single_threaded(struct workqueue_struct *wq){	return wq->singlethread;} static const cpumask_t *wq_cpu_map(struct workqueue_struct *wq){	return is_single_threaded(wq)		? &cpu_singlethread_map : &cpu_populated_map;} staticstruct cpu_workqueue_struct *wq_per_cpu(struct workqueue_struct *wq, int cpu){	if (unlikely(is_single_threaded(wq)))		cpu = singlethread_cpu;	return per_cpu_ptr(wq->cpu_wq, cpu);} /* * Set the workqueue on which a work item is to be run * - Must *only* be called if the pending flag is set */static inline void set_wq_data(struct work_struct *work,				struct cpu_workqueue_struct *cwq){	unsigned long new; 	BUG_ON(!work_pending(work)); 	new = (unsigned long) cwq | (1UL << WORK_STRUCT_PENDING);	new |= WORK_STRUCT_FLAG_MASK & *work_data_bits(work);	atomic_long_set(&work->data, new);} static inlinestruct cpu_workqueue_struct *get_wq_data(struct work_struct *work){	return (void *) (atomic_long_read(&work->data) & WORK_STRUCT_WQ_DATA_MASK);} static void insert_work(struct cpu_workqueue_struct *cwq,				struct work_struct *work, int tail){	set_wq_data(work, cwq);	/*	 * Ensure that we get the right work->data if we see the	 * result of list_add() below, see try_to_grab_pending().	 */	smp_wmb();	if (tail)		list_add_tail(&work->entry, &cwq->worklist);	else		list_add(&work->entry, &cwq->worklist);	wake_up(&cwq->more_work);} /* Preempt must be disabled. */static void __queue_work(struct cpu_workqueue_struct *cwq,			 struct work_struct *work){	unsigned long flags; 	spin_lock_irqsave(&cwq->lock, flags);	insert_work(cwq, work, 1);	spin_unlock_irqrestore(&cwq->lock, flags);} /** * queue_work - queue work on a workqueue * @wq: workqueue to use * @work: work to queue * * Returns 0 if @work was already on a queue, non-zero otherwise. * * We queue the work to the CPU on which it was submitted, but if the CPU dies * it can be processed by another CPU. */int queue_work(struct workqueue_struct *wq, struct work_struct *work){	int ret = 0; 	if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {		BUG_ON(!list_empty(&work->entry));		__queue_work(wq_per_cpu(wq, get_cpu()), work);		put_cpu();		ret = 1;	}	return ret;}EXPORT_SYMBOL_GPL(queue_work); static void delayed_work_timer_fn(unsigned long __data){	struct delayed_work *dwork = (struct delayed_work *)__data;	struct cpu_workqueue_struct *cwq = get_wq_data(&dwork->work);	struct workqueue_struct *wq = cwq->wq; 	__queue_work(wq_per_cpu(wq, smp_processor_id()), &dwork->work);} /** * queue_delayed_work - queue work on a workqueue after delay * @wq: workqueue to use * @dwork: delayable work to queue * @delay: number of jiffies to wait before queueing * * Returns 0 if @work was already on a queue, non-zero otherwise. */int queue_delayed_work(struct workqueue_struct *wq,			struct delayed_work *dwork, unsigned long delay){	if (delay == 0)		return queue_work(wq, &dwork->work); 	return queue_delayed_work_on(-1, wq, dwork, delay);}EXPORT_SYMBOL_GPL(queue_delayed_work); /** * queue_delayed_work_on - queue work on specific CPU after delay * @cpu: CPU number to execute work on * @wq: workqueue to use * @dwork: work to queue * @delay: number of jiffies to wait before queueing * * Returns 0 if @work was already on a queue, non-zero otherwise. */int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,			struct delayed_work *dwork, unsigned long delay){	int ret = 0;	struct timer_list *timer = &dwork->timer;	struct work_struct *work = &dwork->work; 	if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {		BUG_ON(timer_pending(timer));		BUG_ON(!list_empty(&work->entry)); 		timer_stats_timer_set_start_info(&dwork->timer); 		/* This stores cwq for the moment, for the timer_fn */		set_wq_data(work, wq_per_cpu(wq, raw_smp_processor_id()));		timer->expires = jiffies + delay;		timer->data = (unsigned long)dwork;		timer->function = delayed_work_timer_fn; 		if (unlikely(cpu >= 0))			add_timer_on(timer, cpu);		else			add_timer(timer);		ret = 1;	}	return ret;}EXPORT_SYMBOL_GPL(queue_delayed_work_on); static void run_workqueue(struct cpu_workqueue_struct *cwq){	spin_lock_irq(&cwq->lock);	cwq->run_depth++;	if (cwq->run_depth > 3) {		/* morton gets to eat his hat */		printk("%s: recursion depth exceeded: %d\n",			__func__, cwq->run_depth);		dump_stack();	}	while (!list_empty(&cwq->worklist)) {		struct work_struct *work = list_entry(cwq->worklist.next,						struct work_struct, entry);		work_func_t f = work->func;#ifdef CONFIG_LOCKDEP		/*		 * It is permissible to free the struct work_struct		 * from inside the function that is called from it,		 * this we need to take into account for lockdep too.		 * To avoid bogus "held lock freed" warnings as well		 * as problems when looking into work->lockdep_map,		 * make a copy and use that here.		 */		struct lockdep_map lockdep_map = work->lockdep_map;#endif 		cwq->current_work = work;		list_del_init(cwq->worklist.next);		spin_unlock_irq(&cwq->lock); 		BUG_ON(get_wq_data(work) != cwq);		work_clear_pending(work);		lock_acquire(&cwq->wq->lockdep_map, 0, 0, 0, 2, _THIS_IP_);		lock_acquire(&lockdep_map, 0, 0, 0, 2, _THIS_IP_);		f(work);		lock_release(&lockdep_map, 1, _THIS_IP_);		lock_release(&cwq->wq->lockdep_map, 1, _THIS_IP_); 		if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {			printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "					"%s/0x%08x/%d\n",					current->comm, preempt_count(),				       	task_pid_nr(current));			printk(KERN_ERR "    last function: ");			print_symbol("%s\n", (unsigned long)f);			debug_show_held_locks(current);			dump_stack();		} 		spin_lock_irq(&cwq->lock);		cwq->current_work = NULL;	}	cwq->run_depth--;	spin_unlock_irq(&cwq->lock);} static int worker_thread(void *__cwq){	struct cpu_workqueue_struct *cwq = __cwq;	DEFINE_WAIT(wait); 	if (cwq->wq->freezeable)		set_freezable(); 	set_user_nice(current, -5); 	for (;;) {		prepare_to_wait(&cwq->more_work, &wait, TASK_INTERRUPTIBLE);		if (!freezing(current) &&		    !kthread_should_stop() &&		    list_empty(&cwq->worklist))			schedule();		finish_wait(&cwq->more_work, &wait); 		try_to_freeze(); 		if (kthread_should_stop())			break; 		run_workqueue(cwq);	} 	return 0;} struct wq_barrier {	struct work_struct	work;	struct completion	done;}; static void wq_barrier_func(struct work_struct *work){	struct wq_barrier *barr = container_of(work, struct wq_barrier, work);	complete(&barr->done);} static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,					struct wq_barrier *barr, int tail){	INIT_WORK(&barr->work, wq_barrier_func);	__set_bit(WORK_STRUCT_PENDING, work_data_bits(&barr->work)); 	init_completion(&barr->done); 	insert_work(cwq, &barr->work, tail);} static int flush_cpu_workqueue(struct cpu_workqueue_struct *cwq){	int active; 	if (cwq->thread == current) {		/*		 * Probably keventd trying to flush its own queue. So simply run		 * it by hand rather than deadlocking.		 */		run_workqueue(cwq);		active = 1;	} else {		struct wq_barrier barr; 		active = 0;		spin_lock_irq(&cwq->lock);		if (!list_empty(&cwq->worklist) || cwq->current_work != NULL) {			insert_wq_barrier(cwq, &barr, 1);			active = 1;		}		spin_unlock_irq(&cwq->lock); 		if (active)			wait_for_completion(&barr.done);	} 	return active;} /** * flush_workqueue - ensure that any scheduled work has run to completion. * @wq: workqueue to flush * * Forces execution of the workqueue and blocks until its completion. * This is typically used in driver shutdown handlers. * * We sleep until all works which were queued on entry have been handled, * but we are not livelocked by new incoming ones. * * This function used to run the workqueues itself.  Now we just wait for the * helper threads to do it. */void flush_workqueue(struct workqueue_struct *wq){	const cpumask_t *cpu_map = wq_cpu_map(wq);	int cpu; 	might_sleep();	lock_acquire(&wq->lockdep_map, 0, 0, 0, 2, _THIS_IP_);	lock_release(&wq->lockdep_map, 1, _THIS_IP_);	for_each_cpu_mask(cpu, *cpu_map)		flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));}EXPORT_SYMBOL_GPL(flush_workqueue); /* * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit, * so this work can't be re-armed in any way. */static int try_to_grab_pending(struct work_struct *work){	struct cpu_workqueue_struct *cwq;	int ret = -1; 	if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work)))		return 0; 	/*	 * The queueing is in progress, or it is already queued. Try to	 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.	 */ 	cwq = get_wq_data(work);	if (!cwq)		return ret; 	spin_lock_irq(&cwq->lock);	if (!list_empty(&work->entry)) {		/*		 * This work is queued, but perhaps we locked the wrong cwq.		 * In that case we must see the new value after rmb(), see		 * insert_work()->wmb().		 */		smp_rmb();		if (cwq == get_wq_data(work)) {			list_del_init(&work->entry);			ret = 1;		}	}	spin_unlock_irq(&cwq->lock); 	return ret;} static void wait_on_cpu_work(struct cpu_workqueue_struct *cwq,				struct work_struct *work){	struct wq_barrier barr;	int running = 0; 	spin_lock_irq(&cwq->lock);	if (unlikely(cwq->current_work == work)) {		insert_wq_barrier(cwq, &barr, 0);		running = 1;	}	spin_unlock_irq(&cwq->lock); 	if (unlikely(running))		wait_for_completion(&barr.done);} static void wait_on_work(struct work_struct *work){	struct cpu_workqueue_struct *cwq;	struct workqueue_struct *wq;	const cpumask_t *cpu_map;	int cpu; 	might_sleep(); 	lock_acquire(&work->lockdep_map, 0, 0, 0, 2, _THIS_IP_);	lock_release(&work->lockdep_map, 1, _THIS_IP_); 	cwq = get_wq_data(work);	if (!cwq)		return; 	wq = cwq->wq;	cpu_map = wq_cpu_map(wq); 	for_each_cpu_mask(cpu, *cpu_map)		wait_on_cpu_work(per_cpu_ptr(wq->cpu_wq, cpu), work);} static int __cancel_work_timer(struct work_struct *work,				struct timer_list* timer){	int ret; 	do {		ret = (timer && likely(del_timer(timer)));		if (!ret)			ret = try_to_grab_pending(work);		wait_on_work(work);	} while (unlikely(ret < 0)); 	work_clear_pending(work);	return ret;} /**

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