Merge with Linux 2.5.48.

[linux-2.6/linux-mips.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>

#define __KERNEL_SYSCALLS__
#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/mempool.h>
#include <linux/unistd.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
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);

/*
 * When an asynchronous RPC task is activated within a bottom half
 * handler, or while executing another RPC task, it is put on
 * schedq, and rpciod is woken up.
 */
static RPC_WAITQ(schedq, "schedq");

/*
 * 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_WAIT_QUEUE_HEAD(rpciod_idle);
static DECLARE_WAIT_QUEUE_HEAD(rpciod_killer);
static DECLARE_MUTEX(rpciod_sema);
static unsigned int             rpciod_users;
static pid_t                    rpciod_pid;
static int                      rpc_inhibit;

/*
 * Spinlock for wait queues. Access to the latter also has to be
 * interrupt-safe in order to allow timers to wake up sleeping tasks.
 */
static spinlock_t rpc_queue_lock = SPIN_LOCK_UNLOCKED;
/*
 * Spinlock for other critical sections of code.
 */
static spinlock_t rpc_sched_lock = SPIN_LOCK_UNLOCKED;

/*
 * Disable the timer for a given RPC task. Should be called with
 * rpc_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 *);

        spin_lock_bh(&rpc_queue_lock);
        callback = task->tk_timeout_fn;
        task->tk_timeout_fn = NULL;
        spin_unlock_bh(&rpc_queue_lock);
        if (callback) {
                dprintk("RPC: %4d running timer\n", task->tk_pid);
                callback(task);
        }
}

/*
 * 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;
        mod_timer(&task->tk_timer, jiffies + task->tk_timeout);
}

/*
 * Set up a timer for an already sleeping task.
 */
void rpc_add_timer(struct rpc_task *task, rpc_action timer)
{
        spin_lock_bh(&rpc_queue_lock);
        if (!RPC_IS_RUNNING(task))
                __rpc_add_timer(task, timer);
        spin_unlock_bh(&rpc_queue_lock);
}

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

/*
 * 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 inline int
__rpc_add_wait_queue(struct rpc_wait_queue *queue, struct rpc_task *task)
{
        if (task->tk_rpcwait == queue)
                return 0;

        if (task->tk_rpcwait) {
                printk(KERN_WARNING "RPC: doubly enqueued task!\n");
                return -EWOULDBLOCK;
        }
        if (RPC_IS_SWAPPER(task))
                list_add(&task->tk_list, &queue->tasks);
        else
                list_add_tail(&task->tk_list, &queue->tasks);
        task->tk_rpcwait = queue;

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

        return 0;
}

int
rpc_add_wait_queue(struct rpc_wait_queue *q, struct rpc_task *task)
{
        int             result;

        spin_lock_bh(&rpc_queue_lock);
        result = __rpc_add_wait_queue(q, task);
        spin_unlock_bh(&rpc_queue_lock);
        return result;
}

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

        if (!queue)
                return;

        list_del(&task->tk_list);
        task->tk_rpcwait = NULL;

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

void
rpc_remove_wait_queue(struct rpc_task *task)
{
        if (!task->tk_rpcwait)
                return;
        spin_lock_bh(&rpc_queue_lock);
        __rpc_remove_wait_queue(task);
        spin_unlock_bh(&rpc_queue_lock);
}

/*
 * 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 inline void
rpc_make_runnable(struct rpc_task *task)
{
        if (task->tk_timeout_fn) {
                printk(KERN_ERR "RPC: task w/ running timer in rpc_make_runnable!!\n");
                return;
        }
        rpc_set_running(task);
        if (RPC_IS_ASYNC(task)) {
                if (RPC_IS_SLEEPING(task)) {
                        int status;
                        status = __rpc_add_wait_queue(&schedq, task);
                        if (status < 0) {
                                printk(KERN_WARNING "RPC: failed to add task to queue: error: %d!\n", status);
                                task->tk_status = status;
                                return;
                        }
                        rpc_clear_sleeping(task);
                        if (waitqueue_active(&rpciod_idle))
                                wake_up(&rpciod_idle);
                }
        } else {
                rpc_clear_sleeping(task);
                if (waitqueue_active(&task->tk_wait))
                        wake_up(&task->tk_wait);
        }
}

/*
 * Place a newly initialized task on the schedq.
 */
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_set_sleeping(task);
        rpc_make_runnable(task);
}

/*
 *      For other people who may need to wake the I/O daemon
 *      but should (for now) know nothing about its innards
 */
void rpciod_wake_up(void)
{
        if(rpciod_pid==0)
                printk(KERN_ERR "rpciod: wot no daemon?\n");
        if (waitqueue_active(&rpciod_idle))
                wake_up(&rpciod_idle);
}

/*
 * 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)
{
        int status;

        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_set_sleeping(task);
        }

        status = __rpc_add_wait_queue(q, task);
        if (status) {
                printk(KERN_WARNING "RPC: failed to add task to queue: error: %d!\n", status);
                task->tk_status = status;
        } else {
                rpc_clear_running(task);
                if (task->tk_callback) {
                        dprintk(KERN_ERR "RPC: %4d overwrites an active callback\n", task->tk_pid);
                        BUG();
                }
                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(&rpc_queue_lock);
        __rpc_sleep_on(q, task, action, timer);
        spin_unlock_bh(&rpc_queue_lock);
}

/**
 * __rpc_wake_up_task - wake up a single rpc_task
 * @task: task to be woken up
 *
 * Caller must hold rpc_queue_lock
 */
static void
__rpc_wake_up_task(struct rpc_task *task)
{
        dprintk("RPC: %4d __rpc_wake_up_task (now %ld inh %d)\n",
                                        task->tk_pid, jiffies, rpc_inhibit);

#ifdef RPC_DEBUG
        if (task->tk_magic != 0xf00baa) {
                printk(KERN_ERR "RPC: attempt to wake up non-existing task!\n");
                rpc_debug = ~0;
                rpc_show_tasks();
                return;
        }
#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;
        }
        if (RPC_IS_RUNNING(task))
                return;

        __rpc_disable_timer(task);
        if (task->tk_rpcwait != &schedq)
                __rpc_remove_wait_queue(task);

        rpc_make_runnable(task);

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

/*
 * 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_IS_RUNNING(task))
                return;
        spin_lock_bh(&rpc_queue_lock);
        __rpc_wake_up_task(task);
        spin_unlock_bh(&rpc_queue_lock);
}

/*
 * 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(&rpc_queue_lock);
        task_for_first(task, &queue->tasks)
                __rpc_wake_up_task(task);
        spin_unlock_bh(&rpc_queue_lock);

        return task;
}

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

        spin_lock_bh(&rpc_queue_lock);
        while (!list_empty(&queue->tasks))
                task_for_first(task, &queue->tasks)
                        __rpc_wake_up_task(task);
        spin_unlock_bh(&rpc_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 rpc_queue_lock
 */
void
rpc_wake_up_status(struct rpc_wait_queue *queue, int status)
{
        struct rpc_task *task;

        spin_lock_bh(&rpc_queue_lock);
        while (!list_empty(&queue->tasks)) {
                task_for_first(task, &queue->tasks) {
                        task->tk_status = status;
                        __rpc_wake_up_task(task);
                }
        }
        spin_unlock_bh(&rpc_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);

        if (!RPC_IS_RUNNING(task)) {
                printk(KERN_WARNING "RPC: rpc_execute called for sleeping task!!\n");
                return 0;
        }

 restarted:
        while (1) {
                /*
                 * 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;
                        save_callback(task);
                }

                /*
                 * Perform the next FSM step.
                 * tk_action may be NULL when the task has been killed
                 * by someone else.
                 */
                if (RPC_IS_RUNNING(task)) {
                        /*
                         * Garbage collection of pending timers...
                         */
                        rpc_delete_timer(task);
                        if (!task->tk_action)
                                break;
                        task->tk_action(task);
                }

                /*
                 * Check whether task is sleeping.
                 */
                spin_lock_bh(&rpc_queue_lock);
                if (!RPC_IS_RUNNING(task)) {
                        rpc_set_sleeping(task);
                        if (RPC_IS_ASYNC(task)) {
                                spin_unlock_bh(&rpc_queue_lock);
                                return 0;
                        }
                }
                spin_unlock_bh(&rpc_queue_lock);

                while (RPC_IS_SLEEPING(task)) {
                        /* sync task: sleep here */
                        dprintk("RPC: %4d sync task going to sleep\n",
                                                        task->tk_pid);
                        if (current->pid == rpciod_pid)
                                printk(KERN_ERR "RPC: rpciod waiting on sync task!\n");

                        __wait_event(task->tk_wait, !RPC_IS_SLEEPING(task));
                        dprintk("RPC: %4d sync task resuming\n", task->tk_pid);

                        /*
                         * 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 (task->tk_client->cl_intr && signalled()) {
                                dprintk("RPC: %4d got signal\n", task->tk_pid);
                                task->tk_flags |= RPC_TASK_KILLED;
                                rpc_exit(task, -ERESTARTSYS);
                                rpc_wake_up_task(task);
                        }
                }
        }

        if (task->tk_exit) {
                task->tk_exit(task);
                /* 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)
{
        int status = -EIO;
        if (rpc_inhibit) {
                printk(KERN_INFO "RPC: execution inhibited!\n");
                goto out_release;
        }

        status = -EWOULDBLOCK;
        if (task->tk_active) {
                printk(KERN_ERR "RPC: active task was run twice!\n");
                goto out_err;
        }

        task->tk_active = 1;
        rpc_set_running(task);
        return __rpc_execute(task);
 out_release:
        rpc_release_task(task);
 out_err:
        return status;
}

/*
 * This is our own little scheduler for async RPC tasks.
 */
static void
__rpc_schedule(void)
{
        struct rpc_task *task;
        int             count = 0;

        dprintk("RPC:      rpc_schedule enter\n");
        while (1) {
                spin_lock_bh(&rpc_queue_lock);

                task_for_first(task, &schedq.tasks) {
                        __rpc_remove_wait_queue(task);
                        spin_unlock_bh(&rpc_queue_lock);

                        __rpc_execute(task);
                } else {
                        spin_unlock_bh(&rpc_queue_lock);
                        break;
                }

                if (++count >= 200 || need_resched()) {
                        count = 0;
                        schedule();
                }
        }
        dprintk("RPC:      rpc_schedule leave\n");
}

/*
 * 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;
}

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
 */
inline 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;
        init_waitqueue_head(&task->tk_wait);
        if (current->uid != current->fsuid || current->gid != current->fsgid)
                task->tk_flags |= RPC_TASK_SETUID;

        /* Initialize retry counters */
        task->tk_garb_retry = 2;
        task->tk_cred_retry = 2;
        task->tk_suid_retry = 1;

        /* Add to global list of all tasks */
        spin_lock(&rpc_sched_lock);
        list_add(&task->tk_task, &all_tasks);
        spin_unlock(&rpc_sched_lock);

        if (clnt)
                atomic_inc(&clnt->cl_users);

#ifdef RPC_DEBUG
        task->tk_magic = 0xf00baa;
        task->tk_pid = rpc_task_id++;
#endif
        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
        if (task->tk_magic != 0xf00baa) {
                printk(KERN_ERR "RPC: attempt to release a non-existing task!\n");
                rpc_debug = ~0;
                rpc_show_tasks();
                return;
        }
#endif

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

        /* Protect the execution below. */
        spin_lock_bh(&rpc_queue_lock);

        /* Disable timer to prevent zombie wakeup */
        __rpc_disable_timer(task);

        /* Remove from any wait queue we're still on */
        __rpc_remove_wait_queue(task);

        task->tk_active = 0;

        spin_unlock_bh(&rpc_queue_lock);

        /* 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 rpc_queue_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)
                if (task == parent)
                        return parent;

        return NULL;
}

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

        spin_lock_bh(&rpc_queue_lock);
        if ((parent = rpc_find_parent(child)) != NULL) {
                parent->tk_status = child->tk_status;
                __rpc_wake_up_task(parent);
        }
        spin_unlock_bh(&rpc_queue_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(&rpc_queue_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(&rpc_queue_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 (!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 inline int
rpciod_task_pending(void)
{
        return !list_empty(&schedq.tasks);
}


/*
 * This is the rpciod kernel thread
 */
static int
rpciod(void *ptr)
{
        wait_queue_head_t *assassin = (wait_queue_head_t*) ptr;
        int             rounds = 0;

        MOD_INC_USE_COUNT;
        lock_kernel();
        /*
         * Let our maker know we're running ...
         */
        rpciod_pid = current->pid;
        up(&rpciod_running);

        daemonize();

        spin_lock_irq(&current->sig->siglock);
        siginitsetinv(&current->blocked, sigmask(SIGKILL));
        recalc_sigpending();
        spin_unlock_irq(&current->sig->siglock);

        strcpy(current->comm, "rpciod");

        dprintk("RPC: rpciod starting (pid %d)\n", rpciod_pid);
        while (rpciod_users) {
                if (signalled()) {
                        rpciod_killall();
                        flush_signals(current);
                }
                __rpc_schedule();

                if (++rounds >= 64) {   /* safeguard */
                        schedule();
                        rounds = 0;
                }

                if (!rpciod_task_pending()) {
                        dprintk("RPC: rpciod back to sleep\n");
                        wait_event_interruptible(rpciod_idle, rpciod_task_pending());
                        dprintk("RPC: switch to rpciod\n");
                        rounds = 0;
                }
        }

        dprintk("RPC: rpciod shutdown commences\n");
        if (!list_empty(&all_tasks)) {
                printk(KERN_ERR "rpciod: active tasks at shutdown?!\n");
                rpciod_killall();
        }

        rpciod_pid = 0;
        wake_up(assassin);

        dprintk("RPC: rpciod exiting\n");
        unlock_kernel();
        MOD_DEC_USE_COUNT;
        return 0;
}

static void
rpciod_killall(void)
{
        unsigned long flags;

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

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

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

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

void
rpciod_down(void)
{
        unsigned long flags;

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

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

        kill_proc(rpciod_pid, SIGKILL, 1);
        /*
         * Usually rpciod will exit very quickly, so we
         * wait briefly before checking the process id.
         */
        clear_thread_flag(TIF_SIGPENDING);
        yield();
        /*
         * Display a message if we're going to wait longer.
         */
        while (rpciod_pid) {
                dprintk("rpciod_down: waiting for pid %d to exit\n", rpciod_pid);
                if (signalled()) {
                        dprintk("rpciod_down: caught signal\n");
                        break;
                }
                interruptible_sleep_on(&rpciod_killer);
        }
        spin_lock_irqsave(&current->sig->siglock, flags);
        recalc_sigpending();
        spin_unlock_irqrestore(&current->sig->siglock, flags);
out:
        up(&rpciod_sema);
        MOD_DEC_USE_COUNT;
}

#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)
                printk("%05d %04d %04x %06d %8p %6d %8p %08ld %8s %8p %8p\n",
                        t->tk_pid, t->tk_msg.rpc_proc->p_proc,
                        t->tk_flags, t->tk_status,
                        t->tk_client, t->tk_client->cl_prog,
                        t->tk_rqstp, t->tk_timeout,
                        t->tk_rpcwait ? rpc_qname(t->tk_rpcwait) : " <NULL> ",
                        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;
}