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/*

 * 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

};

/* All the per-cpu workqueues on the system, for hotplug cpu to add/remove

   threads to each one as cpus come/go. */

static DEFINE_MUTEX(workqueue_mutex);

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;

}

static

struct 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 inline

struct 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 it was submitted, but there is no

 * guarantee that it will be processed by that CPU.

 */

int fastcall 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);

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 fastcall queue_delayed_work(struct workqueue_struct *wq,

                        struct delayed_work *dwork, unsigned long delay)

{

        timer_stats_timer_set_start_info(&dwork->timer);

        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));

                /* 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",

                        __FUNCTION__, 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 fastcall 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;

}

/**

 * cancel_work_sync - block until a work_struct's callback has terminated

 * @work: the work which is to be flushed

 *

 * Returns true if @work was pending.

 *

 * cancel_work_sync() will cancel the work if it is queued. If the work's

 * callback appears to be running, cancel_work_sync() will block until it

 * has completed.

 *

 * It is possible to use this function if the work re-queues itself. It can

 * cancel the work even if it migrates to another workqueue, however in that

 * case it only guarantees that work->func() has completed on the last queued

 * workqueue.

 *

 * cancel_work_sync(&delayed_work->work) should be used only if ->timer is not

 * pending, otherwise it goes into a busy-wait loop until the timer expires.

 *

 * The caller must ensure that workqueue_struct on which this work was last

 * queued can't be destroyed before this function returns.

 */

int cancel_work_sync(struct work_struct *work)

{

        return __cancel_work_timer(work, NULL);

}

EXPORT_SYMBOL_GPL(cancel_work_sync);

/**

 * cancel_delayed_work_sync - reliably kill off a delayed work.

 * @dwork: the delayed work struct

 *

 * Returns true if @dwork was pending.

 *

 * It is possible to use this function if @dwork rearms itself via queue_work()

 * or queue_delayed_work(). See also the comment for cancel_work_sync().

 */

int cancel_delayed_work_sync(struct delayed_work *dwork)

{

        return __cancel_work_timer(&dwork->work, &dwork->timer);

}

EXPORT_SYMBOL(cancel_delayed_work_sync);

static struct workqueue_struct *keventd_wq __read_mostly;

/**

 * schedule_work - put work task in global workqueue

 * @work: job to be done

 *

 * This puts a job in the kernel-global workqueue.

 */

int fastcall schedule_work(struct work_struct *work)

{

        return queue_work(keventd_wq, work);

}

EXPORT_SYMBOL(schedule_work);

/**

 * schedule_delayed_work - put work task in global workqueue after delay

 * @dwork: job to be done

 * @delay: number of jiffies to wait or 0 for immediate execution

 *

 * After waiting for a given time this puts a job in the kernel-global

 * workqueue.

 */

int fastcall schedule_delayed_work(struct delayed_work *dwork,

                                        unsigned long delay)

{

        timer_stats_timer_set_start_info(&dwork->timer);

        return queue_delayed_work(keventd_wq, dwork, delay);

}

EXPORT_SYMBOL(schedule_delayed_work);

/**

 * schedule_delayed_work_on - queue work in global workqueue on CPU after delay

 * @cpu: cpu to use

 * @dwork: job to be done

 * @delay: number of jiffies to wait

 *

 * After waiting for a given time this puts a job in the kernel-global

 * workqueue on the specified CPU.

 */

int schedule_delayed_work_on(int cpu,

                        struct delayed_work *dwork, unsigned long delay)

{

        return queue_delayed_work_on(cpu, keventd_wq, dwork, delay);

}

EXPORT_SYMBOL(schedule_delayed_work_on);

/**

 * schedule_on_each_cpu - call a function on each online CPU from keventd

 * @func: the function to call

 *

 * Returns zero on success.

 * Returns -ve errno on failure.

 *

 * Appears to be racy against CPU hotplug.

 *

 * schedule_on_each_cpu() is very slow.

 */

int schedule_on_each_cpu(work_func_t func)

{

        int cpu;

        struct work_struct *works;

        works = alloc_percpu(struct work_struct);

        if (!works)

                return -ENOMEM;

        preempt_disable();              /* CPU hotplug */

        for_each_online_cpu(cpu) {

                struct work_struct *work = per_cpu_ptr(works, cpu);

                INIT_WORK(work, func);

                set_bit(WORK_STRUCT_PENDING, work_data_bits(work));

                __queue_work(per_cpu_ptr(keventd_wq->cpu_wq, cpu), work);

        }

        preempt_enable();

        flush_workqueue(keventd_wq);

        free_percpu(works);

        return 0;

}

void flush_scheduled_work(void)

{

        flush_workqueue(keventd_wq);

}

EXPORT_SYMBOL(flush_scheduled_work);

/**

 * execute_in_process_context - reliably execute the routine with user context

 * @fn:         the function to execute

 * @ew:         guaranteed storage for the execute work structure (must

 *              be available when the work executes)

 *

 * Executes the function immediately if process context is available,

 * otherwise schedules the function for delayed execution.

 *

 * Returns:     0 - function was executed

 *              1 - function was scheduled for execution

 */

int execute_in_process_context(work_func_t fn, struct execute_work *ew)

{

        if (!in_interrupt()) {

                fn(&ew->work);

                return 0;

        }

        INIT_WORK(&ew->work, fn);

        schedule_work(&ew->work);

        return 1;

}

EXPORT_SYMBOL_GPL(execute_in_process_context);

int keventd_up(void)

{

        return keventd_wq != NULL;

}

int current_is_keventd(void)

{

        struct cpu_workqueue_struct *cwq;

        int cpu = raw_smp_processor_id(); /* preempt-safe: keventd is per-cpu */

        int ret = 0;

        BUG_ON(!keventd_wq);

        cwq = per_cpu_ptr(keventd_wq->cpu_wq, cpu);

        if (current == cwq->thread)

                ret = 1;

        return ret;

}

static struct cpu_workqueue_struct *

init_cpu_workqueue(struct workqueue_struct *wq, int cpu)

{

        struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);

        cwq->wq = wq;

        spin_lock_init(&cwq->lock);

        INIT_LIST_HEAD(&cwq->worklist);

        init_waitqueue_head(&cwq->more_work);

        return cwq;

}

static int create_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)

{

        struct workqueue_struct *wq = cwq->wq;

        const char *fmt = is_single_threaded(wq) ? "%s" : "%s/%d";

        struct task_struct *p;

        p = kthread_create(worker_thread, cwq, fmt, wq->name, cpu);

        /*

         * Nobody can add the work_struct to this cwq,

         *      if (caller is __create_workqueue)

         *              nobody should see this wq

         *      else // caller is CPU_UP_PREPARE

         *              cpu is not on cpu_online_map

         * so we can abort safely.

         */

        if (IS_ERR(p))

                return PTR_ERR(p);

        cwq->thread = p;