Linux-2.6.12-rc2

[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / net / sunrpc / sched.c

/*
 * linux/net/sunrpc/sched.c
 *
 * Scheduling for synchronous and asynchronous RPC requests.
 *
 * Copyright (C) 1996 Olaf Kirch, <okir@monad.swb.de>
 * 
 * TCP NFS related read + write fixes
 * (C) 1999 Dave Airlie, University of Limerick, Ireland <airlied@linux.ie>
 */

#include <linux/module.h>

#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/mempool.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/spinlock.h>

#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/xprt.h>

#ifdef RPC_DEBUG
#define RPCDBG_FACILITY         RPCDBG_SCHED
#define RPC_TASK_MAGIC_ID       0xf00baa
static int                      rpc_task_id;
#endif

/*
 * RPC slabs and memory pools
 */
#define RPC_BUFFER_MAXSIZE      (2048)
#define RPC_BUFFER_POOLSIZE     (8)
#define RPC_TASK_POOLSIZE       (8)
static kmem_cache_t     *rpc_task_slabp;
static kmem_cache_t     *rpc_buffer_slabp;
static mempool_t        *rpc_task_mempool;
static mempool_t        *rpc_buffer_mempool;

static void                     __rpc_default_timer(struct rpc_task *task);
static void                     rpciod_killall(void);
static void                     rpc_free(struct rpc_task *task);

static void                     rpc_async_schedule(void *);

/*
 * RPC tasks that create another task (e.g. for contacting the portmapper)
 * will wait on this queue for their child's completion
 */
static RPC_WAITQ(childq, "childq");

/*
 * RPC tasks sit here while waiting for conditions to improve.
 */
static RPC_WAITQ(delay_queue, "delayq");

/*
 * All RPC tasks are linked into this list
 */
static LIST_HEAD(all_tasks);

/*
 * rpciod-related stuff
 */
static DECLARE_MUTEX(rpciod_sema);
static unsigned int             rpciod_users;
static struct workqueue_struct *rpciod_workqueue;

/*
 * Spinlock for other critical sections of code.
 */
static DEFINE_SPINLOCK(rpc_sched_lock);

/*
 * Disable the timer for a given RPC task. Should be called with
 * queue->lock and bh_disabled in order to avoid races within
 * rpc_run_timer().
 */
static inline void
__rpc_disable_timer(struct rpc_task *task)
{
        dprintk("RPC: %4d disabling timer\n", task->tk_pid);
        task->tk_timeout_fn = NULL;
        task->tk_timeout = 0;
}

/*
 * Run a timeout function.
 * We use the callback in order to allow __rpc_wake_up_task()
 * and friends to disable the timer synchronously on SMP systems
 * without calling del_timer_sync(). The latter could cause a
 * deadlock if called while we're holding spinlocks...
 */
static void rpc_run_timer(struct rpc_task *task)
{
        void (*callback)(struct rpc_task *);

        callback = task->tk_timeout_fn;
        task->tk_timeout_fn = NULL;
        if (callback && RPC_IS_QUEUED(task)) {
                dprintk("RPC: %4d running timer\n", task->tk_pid);
                callback(task);
        }
        smp_mb__before_clear_bit();
        clear_bit(RPC_TASK_HAS_TIMER, &task->tk_runstate);
        smp_mb__after_clear_bit();
}

/*
 * Set up a timer for the current task.
 */
static inline void
__rpc_add_timer(struct rpc_task *task, rpc_action timer)
{
        if (!task->tk_timeout)
                return;

        dprintk("RPC: %4d setting alarm for %lu ms\n",
                        task->tk_pid, task->tk_timeout * 1000 / HZ);

        if (timer)
                task->tk_timeout_fn = timer;
        else
                task->tk_timeout_fn = __rpc_default_timer;
        set_bit(RPC_TASK_HAS_TIMER, &task->tk_runstate);
        mod_timer(&task->tk_timer, jiffies + task->tk_timeout);
}

/*
 * Delete any timer for the current task. Because we use del_timer_sync(),
 * this function should never be called while holding queue->lock.
 */
static void
rpc_delete_timer(struct rpc_task *task)
{
        if (RPC_IS_QUEUED(task))
                return;
        if (test_and_clear_bit(RPC_TASK_HAS_TIMER, &task->tk_runstate)) {
                del_singleshot_timer_sync(&task->tk_timer);
                dprintk("RPC: %4d deleting timer\n", task->tk_pid);
        }
}

/*
 * Add new request to a priority queue.
 */
static void __rpc_add_wait_queue_priority(struct rpc_wait_queue *queue, struct rpc_task *task)
{
        struct list_head *q;
        struct rpc_task *t;

        INIT_LIST_HEAD(&task->u.tk_wait.links);
        q = &queue->tasks[task->tk_priority];
        if (unlikely(task->tk_priority > queue->maxpriority))
                q = &queue->tasks[queue->maxpriority];
        list_for_each_entry(t, q, u.tk_wait.list) {
                if (t->tk_cookie == task->tk_cookie) {
                        list_add_tail(&task->u.tk_wait.list, &t->u.tk_wait.links);
                        return;
                }
        }
        list_add_tail(&task->u.tk_wait.list, q);
}

/*
 * Add new request to wait queue.
 *
 * Swapper tasks always get inserted at the head of the queue.
 * This should avoid many nasty memory deadlocks and hopefully
 * improve overall performance.
 * Everyone else gets appended to the queue to ensure proper FIFO behavior.
 */
static void __rpc_add_wait_queue(struct rpc_wait_queue *queue, struct rpc_task *task)
{
        BUG_ON (RPC_IS_QUEUED(task));

        if (RPC_IS_PRIORITY(queue))
                __rpc_add_wait_queue_priority(queue, task);
        else if (RPC_IS_SWAPPER(task))
                list_add(&task->u.tk_wait.list, &queue->tasks[0]);
        else
                list_add_tail(&task->u.tk_wait.list, &queue->tasks[0]);
        task->u.tk_wait.rpc_waitq = queue;
        rpc_set_queued(task);

        dprintk("RPC: %4d added to queue %p \"%s\"\n",
                                task->tk_pid, queue, rpc_qname(queue));
}

/*
 * Remove request from a priority queue.
 */
static void __rpc_remove_wait_queue_priority(struct rpc_task *task)
{
        struct rpc_task *t;

        if (!list_empty(&task->u.tk_wait.links)) {
                t = list_entry(task->u.tk_wait.links.next, struct rpc_task, u.tk_wait.list);
                list_move(&t->u.tk_wait.list, &task->u.tk_wait.list);
                list_splice_init(&task->u.tk_wait.links, &t->u.tk_wait.links);
        }
        list_del(&task->u.tk_wait.list);
}

/*
 * Remove request from queue.
 * Note: must be called with spin lock held.
 */
static void __rpc_remove_wait_queue(struct rpc_task *task)
{
        struct rpc_wait_queue *queue;
        queue = task->u.tk_wait.rpc_waitq;

        if (RPC_IS_PRIORITY(queue))
                __rpc_remove_wait_queue_priority(task);
        else
                list_del(&task->u.tk_wait.list);
        dprintk("RPC: %4d removed from queue %p \"%s\"\n",
                                task->tk_pid, queue, rpc_qname(queue));
}

static inline void rpc_set_waitqueue_priority(struct rpc_wait_queue *queue, int priority)
{
        queue->priority = priority;
        queue->count = 1 << (priority * 2);
}

static inline void rpc_set_waitqueue_cookie(struct rpc_wait_queue *queue, unsigned long cookie)
{
        queue->cookie = cookie;
        queue->nr = RPC_BATCH_COUNT;
}

static inline void rpc_reset_waitqueue_priority(struct rpc_wait_queue *queue)
{
        rpc_set_waitqueue_priority(queue, queue->maxpriority);
        rpc_set_waitqueue_cookie(queue, 0);
}

static void __rpc_init_priority_wait_queue(struct rpc_wait_queue *queue, const char *qname, int maxprio)
{
        int i;

        spin_lock_init(&queue->lock);
        for (i = 0; i < ARRAY_SIZE(queue->tasks); i++)
                INIT_LIST_HEAD(&queue->tasks[i]);
        queue->maxpriority = maxprio;
        rpc_reset_waitqueue_priority(queue);
#ifdef RPC_DEBUG
        queue->name = qname;
#endif
}

void rpc_init_priority_wait_queue(struct rpc_wait_queue *queue, const char *qname)
{
        __rpc_init_priority_wait_queue(queue, qname, RPC_PRIORITY_HIGH);
}

void rpc_init_wait_queue(struct rpc_wait_queue *queue, const char *qname)
{
        __rpc_init_priority_wait_queue(queue, qname, 0);
}
EXPORT_SYMBOL(rpc_init_wait_queue);

/*
 * Make an RPC task runnable.
 *
 * Note: If the task is ASYNC, this must be called with 
 * the spinlock held to protect the wait queue operation.
 */
static void rpc_make_runnable(struct rpc_task *task)
{
        int do_ret;

        BUG_ON(task->tk_timeout_fn);
        do_ret = rpc_test_and_set_running(task);
        rpc_clear_queued(task);
        if (do_ret)
                return;
        if (RPC_IS_ASYNC(task)) {
                int status;

                INIT_WORK(&task->u.tk_work, rpc_async_schedule, (void *)task);
                status = queue_work(task->tk_workqueue, &task->u.tk_work);
                if (status < 0) {
                        printk(KERN_WARNING "RPC: failed to add task to queue: error: %d!\n", status);
                        task->tk_status = status;
                        return;
                }
        } else
                wake_up(&task->u.tk_wait.waitq);
}

/*
 * Place a newly initialized task on the workqueue.
 */
static inline void
rpc_schedule_run(struct rpc_task *task)
{
        /* Don't run a child twice! */
        if (RPC_IS_ACTIVATED(task))
                return;
        task->tk_active = 1;
        rpc_make_runnable(task);
}

/*
 * Prepare for sleeping on a wait queue.
 * By always appending tasks to the list we ensure FIFO behavior.
 * NB: An RPC task will only receive interrupt-driven events as long
 * as it's on a wait queue.
 */
static void __rpc_sleep_on(struct rpc_wait_queue *q, struct rpc_task *task,
                        rpc_action action, rpc_action timer)
{
        dprintk("RPC: %4d sleep_on(queue \"%s\" time %ld)\n", task->tk_pid,
                                rpc_qname(q), jiffies);

        if (!RPC_IS_ASYNC(task) && !RPC_IS_ACTIVATED(task)) {
                printk(KERN_ERR "RPC: Inactive synchronous task put to sleep!\n");
                return;
        }

        /* Mark the task as being activated if so needed */
        if (!RPC_IS_ACTIVATED(task))
                task->tk_active = 1;

        __rpc_add_wait_queue(q, task);

        BUG_ON(task->tk_callback != NULL);
        task->tk_callback = action;
        __rpc_add_timer(task, timer);
}

void rpc_sleep_on(struct rpc_wait_queue *q, struct rpc_task *task,
                                rpc_action action, rpc_action timer)
{
        /*
         * Protect the queue operations.
         */
        spin_lock_bh(&q->lock);
        __rpc_sleep_on(q, task, action, timer);
        spin_unlock_bh(&q->lock);
}

/**
 * __rpc_do_wake_up_task - wake up a single rpc_task
 * @task: task to be woken up
 *
 * Caller must hold queue->lock, and have cleared the task queued flag.
 */
static void __rpc_do_wake_up_task(struct rpc_task *task)
{
        dprintk("RPC: %4d __rpc_wake_up_task (now %ld)\n", task->tk_pid, jiffies);

#ifdef RPC_DEBUG
        BUG_ON(task->tk_magic != RPC_TASK_MAGIC_ID);
#endif
        /* Has the task been executed yet? If not, we cannot wake it up! */
        if (!RPC_IS_ACTIVATED(task)) {
                printk(KERN_ERR "RPC: Inactive task (%p) being woken up!\n", task);
                return;
        }

        __rpc_disable_timer(task);
        __rpc_remove_wait_queue(task);

        rpc_make_runnable(task);

        dprintk("RPC:      __rpc_wake_up_task done\n");
}

/*
 * Wake up the specified task
 */
static void __rpc_wake_up_task(struct rpc_task *task)
{
        if (rpc_start_wakeup(task)) {
                if (RPC_IS_QUEUED(task))
                        __rpc_do_wake_up_task(task);
                rpc_finish_wakeup(task);
        }
}

/*
 * Default timeout handler if none specified by user
 */
static void
__rpc_default_timer(struct rpc_task *task)
{
        dprintk("RPC: %d timeout (default timer)\n", task->tk_pid);
        task->tk_status = -ETIMEDOUT;
        rpc_wake_up_task(task);
}

/*
 * Wake up the specified task
 */
void rpc_wake_up_task(struct rpc_task *task)
{
        if (rpc_start_wakeup(task)) {
                if (RPC_IS_QUEUED(task)) {
                        struct rpc_wait_queue *queue = task->u.tk_wait.rpc_waitq;

                        spin_lock_bh(&queue->lock);
                        __rpc_do_wake_up_task(task);
                        spin_unlock_bh(&queue->lock);
                }
                rpc_finish_wakeup(task);
        }
}

/*
 * Wake up the next task on a priority queue.
 */
static struct rpc_task * __rpc_wake_up_next_priority(struct rpc_wait_queue *queue)
{
        struct list_head *q;
        struct rpc_task *task;

        /*
         * Service a batch of tasks from a single cookie.
         */
        q = &queue->tasks[queue->priority];
        if (!list_empty(q)) {
                task = list_entry(q->next, struct rpc_task, u.tk_wait.list);
                if (queue->cookie == task->tk_cookie) {
                        if (--queue->nr)
                                goto out;
                        list_move_tail(&task->u.tk_wait.list, q);
                }
                /*
                 * Check if we need to switch queues.
                 */
                if (--queue->count)
                        goto new_cookie;
        }

        /*
         * Service the next queue.
         */
        do {
                if (q == &queue->tasks[0])
                        q = &queue->tasks[queue->maxpriority];
                else
                        q = q - 1;
                if (!list_empty(q)) {
                        task = list_entry(q->next, struct rpc_task, u.tk_wait.list);
                        goto new_queue;
                }
        } while (q != &queue->tasks[queue->priority]);

        rpc_reset_waitqueue_priority(queue);
        return NULL;

new_queue:
        rpc_set_waitqueue_priority(queue, (unsigned int)(q - &queue->tasks[0]));
new_cookie:
        rpc_set_waitqueue_cookie(queue, task->tk_cookie);
out:
        __rpc_wake_up_task(task);
        return task;
}

/*
 * Wake up the next task on the wait queue.
 */
struct rpc_task * rpc_wake_up_next(struct rpc_wait_queue *queue)
{
        struct rpc_task *task = NULL;

        dprintk("RPC:      wake_up_next(%p \"%s\")\n", queue, rpc_qname(queue));
        spin_lock_bh(&queue->lock);
        if (RPC_IS_PRIORITY(queue))
                task = __rpc_wake_up_next_priority(queue);
        else {
                task_for_first(task, &queue->tasks[0])
                        __rpc_wake_up_task(task);
        }
        spin_unlock_bh(&queue->lock);

        return task;
}

/**
 * rpc_wake_up - wake up all rpc_tasks
 * @queue: rpc_wait_queue on which the tasks are sleeping
 *
 * Grabs queue->lock
 */
void rpc_wake_up(struct rpc_wait_queue *queue)
{
        struct rpc_task *task;

        struct list_head *head;
        spin_lock_bh(&queue->lock);
        head = &queue->tasks[queue->maxpriority];
        for (;;) {
                while (!list_empty(head)) {
                        task = list_entry(head->next, struct rpc_task, u.tk_wait.list);
                        __rpc_wake_up_task(task);
                }
                if (head == &queue->tasks[0])
                        break;
                head--;
        }
        spin_unlock_bh(&queue->lock);
}

/**
 * rpc_wake_up_status - wake up all rpc_tasks and set their status value.
 * @queue: rpc_wait_queue on which the tasks are sleeping
 * @status: status value to set
 *
 * Grabs queue->lock
 */
void rpc_wake_up_status(struct rpc_wait_queue *queue, int status)
{
        struct list_head *head;
        struct rpc_task *task;

        spin_lock_bh(&queue->lock);
        head = &queue->tasks[queue->maxpriority];
        for (;;) {
                while (!list_empty(head)) {
                        task = list_entry(head->next, struct rpc_task, u.tk_wait.list);
                        task->tk_status = status;
                        __rpc_wake_up_task(task);
                }
                if (head == &queue->tasks[0])
                        break;
                head--;
        }
        spin_unlock_bh(&queue->lock);
}

/*
 * Run a task at a later time
 */
static void     __rpc_atrun(struct rpc_task *);
void
rpc_delay(struct rpc_task *task, unsigned long delay)
{
        task->tk_timeout = delay;
        rpc_sleep_on(&delay_queue, task, NULL, __rpc_atrun);
}

static void
__rpc_atrun(struct rpc_task *task)
{
        task->tk_status = 0;
        rpc_wake_up_task(task);
}

/*
 * This is the RPC `scheduler' (or rather, the finite state machine).
 */
static int __rpc_execute(struct rpc_task *task)
{
        int             status = 0;

        dprintk("RPC: %4d rpc_execute flgs %x\n",
                                task->tk_pid, task->tk_flags);

        BUG_ON(RPC_IS_QUEUED(task));

 restarted:
        while (1) {
                /*
                 * Garbage collection of pending timers...
                 */
                rpc_delete_timer(task);

                /*
                 * Execute any pending callback.
                 */
                if (RPC_DO_CALLBACK(task)) {
                        /* Define a callback save pointer */
                        void (*save_callback)(struct rpc_task *);
        
                        /* 
                         * If a callback exists, save it, reset it,
                         * call it.
                         * The save is needed to stop from resetting
                         * another callback set within the callback handler
                         * - Dave
                         */
                        save_callback=task->tk_callback;
                        task->tk_callback=NULL;
                        lock_kernel();
                        save_callback(task);
                        unlock_kernel();
                }

                /*
                 * Perform the next FSM step.
                 * tk_action may be NULL when the task has been killed
                 * by someone else.
                 */
                if (!RPC_IS_QUEUED(task)) {
                        if (!task->tk_action)
                                break;
                        lock_kernel();
                        task->tk_action(task);
                        unlock_kernel();
                }

                /*
                 * Lockless check for whether task is sleeping or not.
                 */
                if (!RPC_IS_QUEUED(task))
                        continue;
                rpc_clear_running(task);
                if (RPC_IS_ASYNC(task)) {
                        /* Careful! we may have raced... */
                        if (RPC_IS_QUEUED(task))
                                return 0;
                        if (rpc_test_and_set_running(task))
                                return 0;
                        continue;
                }

                /* sync task: sleep here */
                dprintk("RPC: %4d sync task going to sleep\n", task->tk_pid);
                if (RPC_TASK_UNINTERRUPTIBLE(task)) {
                        __wait_event(task->u.tk_wait.waitq, !RPC_IS_QUEUED(task));
                } else {
                        __wait_event_interruptible(task->u.tk_wait.waitq, !RPC_IS_QUEUED(task), status);
                        /*
                         * When a sync task receives a signal, it exits with
                         * -ERESTARTSYS. In order to catch any callbacks that
                         * clean up after sleeping on some queue, we don't
                         * break the loop here, but go around once more.
                         */
                        if (status == -ERESTARTSYS) {
                                dprintk("RPC: %4d got signal\n", task->tk_pid);
                                task->tk_flags |= RPC_TASK_KILLED;
                                rpc_exit(task, -ERESTARTSYS);
                                rpc_wake_up_task(task);
                        }
                }
                rpc_set_running(task);
                dprintk("RPC: %4d sync task resuming\n", task->tk_pid);
        }

        if (task->tk_exit) {
                lock_kernel();
                task->tk_exit(task);
                unlock_kernel();
                /* If tk_action is non-null, the user wants us to restart */
                if (task->tk_action) {
                        if (!RPC_ASSASSINATED(task)) {
                                /* Release RPC slot and buffer memory */
                                if (task->tk_rqstp)
                                        xprt_release(task);
                                rpc_free(task);
                                goto restarted;
                        }
                        printk(KERN_ERR "RPC: dead task tries to walk away.\n");
                }
        }

        dprintk("RPC: %4d exit() = %d\n", task->tk_pid, task->tk_status);
        status = task->tk_status;

        /* Release all resources associated with the task */
        rpc_release_task(task);
        return status;
}

/*
 * User-visible entry point to the scheduler.
 *
 * This may be called recursively if e.g. an async NFS task updates
 * the attributes and finds that dirty pages must be flushed.
 * NOTE: Upon exit of this function the task is guaranteed to be
 *       released. In particular note that tk_release() will have
 *       been called, so your task memory may have been freed.
 */
int
rpc_execute(struct rpc_task *task)
{
        BUG_ON(task->tk_active);

        task->tk_active = 1;
        rpc_set_running(task);
        return __rpc_execute(task);
}

static void rpc_async_schedule(void *arg)
{
        __rpc_execute((struct rpc_task *)arg);
}

/*
 * Allocate memory for RPC purposes.
 *
 * We try to ensure that some NFS reads and writes can always proceed
 * by using a mempool when allocating 'small' buffers.
 * In order to avoid memory starvation triggering more writebacks of
 * NFS requests, we use GFP_NOFS rather than GFP_KERNEL.
 */
void *
rpc_malloc(struct rpc_task *task, size_t size)
{
        int     gfp;

        if (task->tk_flags & RPC_TASK_SWAPPER)
                gfp = GFP_ATOMIC;
        else
                gfp = GFP_NOFS;

        if (size > RPC_BUFFER_MAXSIZE) {
                task->tk_buffer =  kmalloc(size, gfp);
                if (task->tk_buffer)
                        task->tk_bufsize = size;
        } else {
                task->tk_buffer =  mempool_alloc(rpc_buffer_mempool, gfp);
                if (task->tk_buffer)
                        task->tk_bufsize = RPC_BUFFER_MAXSIZE;
        }
        return task->tk_buffer;
}

static void
rpc_free(struct rpc_task *task)
{
        if (task->tk_buffer) {
                if (task->tk_bufsize == RPC_BUFFER_MAXSIZE)
                        mempool_free(task->tk_buffer, rpc_buffer_mempool);
                else
                        kfree(task->tk_buffer);
                task->tk_buffer = NULL;
                task->tk_bufsize = 0;
        }
}

/*
 * Creation and deletion of RPC task structures
 */
void rpc_init_task(struct rpc_task *task, struct rpc_clnt *clnt, rpc_action callback, int flags)
{
        memset(task, 0, sizeof(*task));
        init_timer(&task->tk_timer);
        task->tk_timer.data     = (unsigned long) task;
        task->tk_timer.function = (void (*)(unsigned long)) rpc_run_timer;
        task->tk_client = clnt;
        task->tk_flags  = flags;
        task->tk_exit   = callback;

        /* Initialize retry counters */
        task->tk_garb_retry = 2;
        task->tk_cred_retry = 2;

        task->tk_priority = RPC_PRIORITY_NORMAL;
        task->tk_cookie = (unsigned long)current;

        /* Initialize workqueue for async tasks */
        task->tk_workqueue = rpciod_workqueue;
        if (!RPC_IS_ASYNC(task))
                init_waitqueue_head(&task->u.tk_wait.waitq);

        if (clnt) {
                atomic_inc(&clnt->cl_users);
                if (clnt->cl_softrtry)
                        task->tk_flags |= RPC_TASK_SOFT;
                if (!clnt->cl_intr)
                        task->tk_flags |= RPC_TASK_NOINTR;
        }

#ifdef RPC_DEBUG
        task->tk_magic = RPC_TASK_MAGIC_ID;
        task->tk_pid = rpc_task_id++;
#endif
        /* Add to global list of all tasks */
        spin_lock(&rpc_sched_lock);
        list_add_tail(&task->tk_task, &all_tasks);
        spin_unlock(&rpc_sched_lock);

        dprintk("RPC: %4d new task procpid %d\n", task->tk_pid,
                                current->pid);
}

static struct rpc_task *
rpc_alloc_task(void)
{
        return (struct rpc_task *)mempool_alloc(rpc_task_mempool, GFP_NOFS);
}

static void
rpc_default_free_task(struct rpc_task *task)
{
        dprintk("RPC: %4d freeing task\n", task->tk_pid);
        mempool_free(task, rpc_task_mempool);
}

/*
 * Create a new task for the specified client.  We have to
 * clean up after an allocation failure, as the client may
 * have specified "oneshot".
 */
struct rpc_task *
rpc_new_task(struct rpc_clnt *clnt, rpc_action callback, int flags)
{
        struct rpc_task *task;

        task = rpc_alloc_task();
        if (!task)
                goto cleanup;

        rpc_init_task(task, clnt, callback, flags);

        /* Replace tk_release */
        task->tk_release = rpc_default_free_task;

        dprintk("RPC: %4d allocated task\n", task->tk_pid);
        task->tk_flags |= RPC_TASK_DYNAMIC;
out:
        return task;

cleanup:
        /* Check whether to release the client */
        if (clnt) {
                printk("rpc_new_task: failed, users=%d, oneshot=%d\n",
                        atomic_read(&clnt->cl_users), clnt->cl_oneshot);
                atomic_inc(&clnt->cl_users); /* pretend we were used ... */
                rpc_release_client(clnt);
        }
        goto out;
}

void rpc_release_task(struct rpc_task *task)
{
        dprintk("RPC: %4d release task\n", task->tk_pid);

#ifdef RPC_DEBUG
        BUG_ON(task->tk_magic != RPC_TASK_MAGIC_ID);
#endif

        /* Remove from global task list */
        spin_lock(&rpc_sched_lock);
        list_del(&task->tk_task);
        spin_unlock(&rpc_sched_lock);

        BUG_ON (RPC_IS_QUEUED(task));
        task->tk_active = 0;

        /* Synchronously delete any running timer */
        rpc_delete_timer(task);

        /* Release resources */
        if (task->tk_rqstp)
                xprt_release(task);
        if (task->tk_msg.rpc_cred)
                rpcauth_unbindcred(task);
        rpc_free(task);
        if (task->tk_client) {
                rpc_release_client(task->tk_client);
                task->tk_client = NULL;
        }

#ifdef RPC_DEBUG
        task->tk_magic = 0;
#endif
        if (task->tk_release)
                task->tk_release(task);
}

/**
 * rpc_find_parent - find the parent of a child task.
 * @child: child task
 *
 * Checks that the parent task is still sleeping on the
 * queue 'childq'. If so returns a pointer to the parent.
 * Upon failure returns NULL.
 *
 * Caller must hold childq.lock
 */
static inline struct rpc_task *rpc_find_parent(struct rpc_task *child)
{
        struct rpc_task *task, *parent;
        struct list_head *le;

        parent = (struct rpc_task *) child->tk_calldata;
        task_for_each(task, le, &childq.tasks[0])
                if (task == parent)
                        return parent;

        return NULL;
}

static void rpc_child_exit(struct rpc_task *child)
{
        struct rpc_task *parent;

        spin_lock_bh(&childq.lock);
        if ((parent = rpc_find_parent(child)) != NULL) {
                parent->tk_status = child->tk_status;
                __rpc_wake_up_task(parent);
        }
        spin_unlock_bh(&childq.lock);
}

/*
 * Note: rpc_new_task releases the client after a failure.
 */
struct rpc_task *
rpc_new_child(struct rpc_clnt *clnt, struct rpc_task *parent)
{
        struct rpc_task *task;

        task = rpc_new_task(clnt, NULL, RPC_TASK_ASYNC | RPC_TASK_CHILD);
        if (!task)
                goto fail;
        task->tk_exit = rpc_child_exit;
        task->tk_calldata = parent;
        return task;

fail:
        parent->tk_status = -ENOMEM;
        return NULL;
}

void rpc_run_child(struct rpc_task *task, struct rpc_task *child, rpc_action func)
{
        spin_lock_bh(&childq.lock);
        /* N.B. Is it possible for the child to have already finished? */
        __rpc_sleep_on(&childq, task, func, NULL);
        rpc_schedule_run(child);
        spin_unlock_bh(&childq.lock);
}

/*
 * Kill all tasks for the given client.
 * XXX: kill their descendants as well?
 */
void rpc_killall_tasks(struct rpc_clnt *clnt)
{
        struct rpc_task *rovr;
        struct list_head *le;

        dprintk("RPC:      killing all tasks for client %p\n", clnt);

        /*
         * Spin lock all_tasks to prevent changes...
         */
        spin_lock(&rpc_sched_lock);
        alltask_for_each(rovr, le, &all_tasks) {
                if (! RPC_IS_ACTIVATED(rovr))
                        continue;
                if (!clnt || rovr->tk_client == clnt) {
                        rovr->tk_flags |= RPC_TASK_KILLED;
                        rpc_exit(rovr, -EIO);
                        rpc_wake_up_task(rovr);
                }
        }
        spin_unlock(&rpc_sched_lock);
}

static DECLARE_MUTEX_LOCKED(rpciod_running);

static void rpciod_killall(void)
{
        unsigned long flags;

        while (!list_empty(&all_tasks)) {
                clear_thread_flag(TIF_SIGPENDING);
                rpc_killall_tasks(NULL);
                flush_workqueue(rpciod_workqueue);
                if (!list_empty(&all_tasks)) {
                        dprintk("rpciod_killall: waiting for tasks to exit\n");
                        yield();
                }
        }

        spin_lock_irqsave(&current->sighand->siglock, flags);
        recalc_sigpending();
        spin_unlock_irqrestore(&current->sighand->siglock, flags);
}

/*
 * Start up the rpciod process if it's not already running.
 */
int
rpciod_up(void)
{
        struct workqueue_struct *wq;
        int error = 0;

        down(&rpciod_sema);
        dprintk("rpciod_up: users %d\n", rpciod_users);
        rpciod_users++;
        if (rpciod_workqueue)
                goto out;
        /*
         * If there's no pid, we should be the first user.
         */
        if (rpciod_users > 1)
                printk(KERN_WARNING "rpciod_up: no workqueue, %d users??\n", rpciod_users);
        /*
         * Create the rpciod thread and wait for it to start.
         */
        error = -ENOMEM;
        wq = create_workqueue("rpciod");
        if (wq == NULL) {
                printk(KERN_WARNING "rpciod_up: create workqueue failed, error=%d\n", error);
                rpciod_users--;
                goto out;
        }
        rpciod_workqueue = wq;
        error = 0;
out:
        up(&rpciod_sema);
        return error;
}

void
rpciod_down(void)
{
        down(&rpciod_sema);
        dprintk("rpciod_down sema %d\n", rpciod_users);
        if (rpciod_users) {
                if (--rpciod_users)
                        goto out;
        } else
                printk(KERN_WARNING "rpciod_down: no users??\n");

        if (!rpciod_workqueue) {
                dprintk("rpciod_down: Nothing to do!\n");
                goto out;
        }
        rpciod_killall();

        destroy_workqueue(rpciod_workqueue);
        rpciod_workqueue = NULL;
 out:
        up(&rpciod_sema);
}

#ifdef RPC_DEBUG
void rpc_show_tasks(void)
{
        struct list_head *le;
        struct rpc_task *t;

        spin_lock(&rpc_sched_lock);
        if (list_empty(&all_tasks)) {
                spin_unlock(&rpc_sched_lock);
                return;
        }
        printk("-pid- proc flgs status -client- -prog- --rqstp- -timeout "
                "-rpcwait -action- --exit--\n");
        alltask_for_each(t, le, &all_tasks) {
                const char *rpc_waitq = "none";

                if (RPC_IS_QUEUED(t))
                        rpc_waitq = rpc_qname(t->u.tk_wait.rpc_waitq);

                printk("%05d %04d %04x %06d %8p %6d %8p %08ld %8s %8p %8p\n",
                        t->tk_pid,
                        (t->tk_msg.rpc_proc ? t->tk_msg.rpc_proc->p_proc : -1),
                        t->tk_flags, t->tk_status,
                        t->tk_client,
                        (t->tk_client ? t->tk_client->cl_prog : 0),
                        t->tk_rqstp, t->tk_timeout,
                        rpc_waitq,
                        t->tk_action, t->tk_exit);
        }
        spin_unlock(&rpc_sched_lock);
}
#endif

void
rpc_destroy_mempool(void)
{
        if (rpc_buffer_mempool)
                mempool_destroy(rpc_buffer_mempool);
        if (rpc_task_mempool)
                mempool_destroy(rpc_task_mempool);
        if (rpc_task_slabp && kmem_cache_destroy(rpc_task_slabp))
                printk(KERN_INFO "rpc_task: not all structures were freed\n");
        if (rpc_buffer_slabp && kmem_cache_destroy(rpc_buffer_slabp))
                printk(KERN_INFO "rpc_buffers: not all structures were freed\n");
}

int
rpc_init_mempool(void)
{
        rpc_task_slabp = kmem_cache_create("rpc_tasks",
                                             sizeof(struct rpc_task),
                                             0, SLAB_HWCACHE_ALIGN,
                                             NULL, NULL);
        if (!rpc_task_slabp)
                goto err_nomem;
        rpc_buffer_slabp = kmem_cache_create("rpc_buffers",
                                             RPC_BUFFER_MAXSIZE,
                                             0, SLAB_HWCACHE_ALIGN,
                                             NULL, NULL);
        if (!rpc_buffer_slabp)
                goto err_nomem;
        rpc_task_mempool = mempool_create(RPC_TASK_POOLSIZE,
                                            mempool_alloc_slab,
                                            mempool_free_slab,
                                            rpc_task_slabp);
        if (!rpc_task_mempool)
                goto err_nomem;
        rpc_buffer_mempool = mempool_create(RPC_BUFFER_POOLSIZE,
                                            mempool_alloc_slab,
                                            mempool_free_slab,
                                            rpc_buffer_slabp);
        if (!rpc_buffer_mempool)
                goto err_nomem;
        return 0;
err_nomem:
        rpc_destroy_mempool();
        return -ENOMEM;
}