libata: unify mechanism to request follow-up SRST

[linux-2.6/pdupreez.git] / net / sched / sch_generic.c

/*
 * net/sched/sch_generic.c      Generic packet scheduler routines.
 *
 *              This program is free software; you can redistribute it and/or
 *              modify it under the terms of the GNU General Public License
 *              as published by the Free Software Foundation; either version
 *              2 of the License, or (at your option) any later version.
 *
 * Authors:     Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
 *              Jamal Hadi Salim, <hadi@cyberus.ca> 990601
 *              - Ingress support
 */

#include <linux/bitops.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/rtnetlink.h>
#include <linux/init.h>
#include <linux/rcupdate.h>
#include <linux/list.h>
#include <net/pkt_sched.h>

/* Main transmission queue. */

/* Modifications to data participating in scheduling must be protected with
 * dev->queue_lock spinlock.
 *
 * The idea is the following:
 * - enqueue, dequeue are serialized via top level device
 *   spinlock dev->queue_lock.
 * - ingress filtering is serialized via top level device
 *   spinlock dev->ingress_lock.
 * - updates to tree and tree walking are only done under the rtnl mutex.
 */

void qdisc_lock_tree(struct net_device *dev)
        __acquires(dev->queue_lock)
        __acquires(dev->ingress_lock)
{
        spin_lock_bh(&dev->queue_lock);
        spin_lock(&dev->ingress_lock);
}
EXPORT_SYMBOL(qdisc_lock_tree);

void qdisc_unlock_tree(struct net_device *dev)
        __releases(dev->ingress_lock)
        __releases(dev->queue_lock)
{
        spin_unlock(&dev->ingress_lock);
        spin_unlock_bh(&dev->queue_lock);
}
EXPORT_SYMBOL(qdisc_unlock_tree);

static inline int qdisc_qlen(struct Qdisc *q)
{
        return q->q.qlen;
}

static inline int dev_requeue_skb(struct sk_buff *skb, struct net_device *dev,
                                  struct Qdisc *q)
{
        if (unlikely(skb->next))
                dev->gso_skb = skb;
        else
                q->ops->requeue(skb, q);

        netif_schedule(dev);
        return 0;
}

static inline struct sk_buff *dev_dequeue_skb(struct net_device *dev,
                                              struct Qdisc *q)
{
        struct sk_buff *skb;

        if ((skb = dev->gso_skb))
                dev->gso_skb = NULL;
        else
                skb = q->dequeue(q);

        return skb;
}

static inline int handle_dev_cpu_collision(struct sk_buff *skb,
                                           struct net_device *dev,
                                           struct Qdisc *q)
{
        int ret;

        if (unlikely(dev->xmit_lock_owner == smp_processor_id())) {
                /*
                 * Same CPU holding the lock. It may be a transient
                 * configuration error, when hard_start_xmit() recurses. We
                 * detect it by checking xmit owner and drop the packet when
                 * deadloop is detected. Return OK to try the next skb.
                 */
                kfree_skb(skb);
                if (net_ratelimit())
                        printk(KERN_WARNING "Dead loop on netdevice %s, "
                               "fix it urgently!\n", dev->name);
                ret = qdisc_qlen(q);
        } else {
                /*
                 * Another cpu is holding lock, requeue & delay xmits for
                 * some time.
                 */
                __get_cpu_var(netdev_rx_stat).cpu_collision++;
                ret = dev_requeue_skb(skb, dev, q);
        }

        return ret;
}

/*
 * NOTE: Called under dev->queue_lock with locally disabled BH.
 *
 * __LINK_STATE_QDISC_RUNNING guarantees only one CPU can process this
 * device at a time. dev->queue_lock serializes queue accesses for
 * this device AND dev->qdisc pointer itself.
 *
 *  netif_tx_lock serializes accesses to device driver.
 *
 *  dev->queue_lock and netif_tx_lock are mutually exclusive,
 *  if one is grabbed, another must be free.
 *
 * Note, that this procedure can be called by a watchdog timer
 *
 * Returns to the caller:
 *                              0  - queue is empty or throttled.
 *                              >0 - queue is not empty.
 *
 */
static inline int qdisc_restart(struct net_device *dev)
{
        struct Qdisc *q = dev->qdisc;
        struct sk_buff *skb;
        int ret = NETDEV_TX_BUSY;

        /* Dequeue packet */
        if (unlikely((skb = dev_dequeue_skb(dev, q)) == NULL))
                return 0;


        /* And release queue */
        spin_unlock(&dev->queue_lock);

        HARD_TX_LOCK(dev, smp_processor_id());
        if (!netif_subqueue_stopped(dev, skb))
                ret = dev_hard_start_xmit(skb, dev);
        HARD_TX_UNLOCK(dev);

        spin_lock(&dev->queue_lock);
        q = dev->qdisc;

        switch (ret) {
        case NETDEV_TX_OK:
                /* Driver sent out skb successfully */
                ret = qdisc_qlen(q);
                break;

        case NETDEV_TX_LOCKED:
                /* Driver try lock failed */
                ret = handle_dev_cpu_collision(skb, dev, q);
                break;

        default:
                /* Driver returned NETDEV_TX_BUSY - requeue skb */
                if (unlikely (ret != NETDEV_TX_BUSY && net_ratelimit()))
                        printk(KERN_WARNING "BUG %s code %d qlen %d\n",
                               dev->name, ret, q->q.qlen);

                ret = dev_requeue_skb(skb, dev, q);
                break;
        }

        return ret;
}

void __qdisc_run(struct net_device *dev)
{
        unsigned long start_time = jiffies;

        while (qdisc_restart(dev)) {
                if (netif_queue_stopped(dev))
                        break;

                /*
                 * Postpone processing if
                 * 1. another process needs the CPU;
                 * 2. we've been doing it for too long.
                 */
                if (need_resched() || jiffies != start_time) {
                        netif_schedule(dev);
                        break;
                }
        }

        clear_bit(__LINK_STATE_QDISC_RUNNING, &dev->state);
}

static void dev_watchdog(unsigned long arg)
{
        struct net_device *dev = (struct net_device *)arg;

        netif_tx_lock(dev);
        if (dev->qdisc != &noop_qdisc) {
                if (netif_device_present(dev) &&
                    netif_running(dev) &&
                    netif_carrier_ok(dev)) {
                        if (netif_queue_stopped(dev) &&
                            time_after(jiffies, dev->trans_start + dev->watchdog_timeo)) {

                                printk(KERN_INFO "NETDEV WATCHDOG: %s: transmit timed out\n",
                                       dev->name);
                                dev->tx_timeout(dev);
                        }
                        if (!mod_timer(&dev->watchdog_timer, round_jiffies(jiffies + dev->watchdog_timeo)))
                                dev_hold(dev);
                }
        }
        netif_tx_unlock(dev);

        dev_put(dev);
}

void __netdev_watchdog_up(struct net_device *dev)
{
        if (dev->tx_timeout) {
                if (dev->watchdog_timeo <= 0)
                        dev->watchdog_timeo = 5*HZ;
                if (!mod_timer(&dev->watchdog_timer,
                               round_jiffies(jiffies + dev->watchdog_timeo)))
                        dev_hold(dev);
        }
}

static void dev_watchdog_up(struct net_device *dev)
{
        __netdev_watchdog_up(dev);
}

static void dev_watchdog_down(struct net_device *dev)
{
        netif_tx_lock_bh(dev);
        if (del_timer(&dev->watchdog_timer))
                dev_put(dev);
        netif_tx_unlock_bh(dev);
}

/**
 *      netif_carrier_on - set carrier
 *      @dev: network device
 *
 * Device has detected that carrier.
 */
void netif_carrier_on(struct net_device *dev)
{
        if (test_and_clear_bit(__LINK_STATE_NOCARRIER, &dev->state)) {
                linkwatch_fire_event(dev);
                if (netif_running(dev))
                        __netdev_watchdog_up(dev);
        }
}
EXPORT_SYMBOL(netif_carrier_on);

/**
 *      netif_carrier_off - clear carrier
 *      @dev: network device
 *
 * Device has detected loss of carrier.
 */
void netif_carrier_off(struct net_device *dev)
{
        if (!test_and_set_bit(__LINK_STATE_NOCARRIER, &dev->state))
                linkwatch_fire_event(dev);
}
EXPORT_SYMBOL(netif_carrier_off);

/* "NOOP" scheduler: the best scheduler, recommended for all interfaces
   under all circumstances. It is difficult to invent anything faster or
   cheaper.
 */

static int noop_enqueue(struct sk_buff *skb, struct Qdisc * qdisc)
{
        kfree_skb(skb);
        return NET_XMIT_CN;
}

static struct sk_buff *noop_dequeue(struct Qdisc * qdisc)
{
        return NULL;
}

static int noop_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
{
        if (net_ratelimit())
                printk(KERN_DEBUG "%s deferred output. It is buggy.\n",
                       skb->dev->name);
        kfree_skb(skb);
        return NET_XMIT_CN;
}

struct Qdisc_ops noop_qdisc_ops __read_mostly = {
        .id             =       "noop",
        .priv_size      =       0,
        .enqueue        =       noop_enqueue,
        .dequeue        =       noop_dequeue,
        .requeue        =       noop_requeue,
        .owner          =       THIS_MODULE,
};

struct Qdisc noop_qdisc = {
        .enqueue        =       noop_enqueue,
        .dequeue        =       noop_dequeue,
        .flags          =       TCQ_F_BUILTIN,
        .ops            =       &noop_qdisc_ops,
        .list           =       LIST_HEAD_INIT(noop_qdisc.list),
};
EXPORT_SYMBOL(noop_qdisc);

static struct Qdisc_ops noqueue_qdisc_ops __read_mostly = {
        .id             =       "noqueue",
        .priv_size      =       0,
        .enqueue        =       noop_enqueue,
        .dequeue        =       noop_dequeue,
        .requeue        =       noop_requeue,
        .owner          =       THIS_MODULE,
};

static struct Qdisc noqueue_qdisc = {
        .enqueue        =       NULL,
        .dequeue        =       noop_dequeue,
        .flags          =       TCQ_F_BUILTIN,
        .ops            =       &noqueue_qdisc_ops,
        .list           =       LIST_HEAD_INIT(noqueue_qdisc.list),
};


static const u8 prio2band[TC_PRIO_MAX+1] =
        { 1, 2, 2, 2, 1, 2, 0, 0 , 1, 1, 1, 1, 1, 1, 1, 1 };

/* 3-band FIFO queue: old style, but should be a bit faster than
   generic prio+fifo combination.
 */

#define PFIFO_FAST_BANDS 3

static inline struct sk_buff_head *prio2list(struct sk_buff *skb,
                                             struct Qdisc *qdisc)
{
        struct sk_buff_head *list = qdisc_priv(qdisc);
        return list + prio2band[skb->priority & TC_PRIO_MAX];
}

static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc* qdisc)
{
        struct sk_buff_head *list = prio2list(skb, qdisc);

        if (skb_queue_len(list) < qdisc->dev->tx_queue_len) {
                qdisc->q.qlen++;
                return __qdisc_enqueue_tail(skb, qdisc, list);
        }

        return qdisc_drop(skb, qdisc);
}

static struct sk_buff *pfifo_fast_dequeue(struct Qdisc* qdisc)
{
        int prio;
        struct sk_buff_head *list = qdisc_priv(qdisc);

        for (prio = 0; prio < PFIFO_FAST_BANDS; prio++) {
                if (!skb_queue_empty(list + prio)) {
                        qdisc->q.qlen--;
                        return __qdisc_dequeue_head(qdisc, list + prio);
                }
        }

        return NULL;
}

static int pfifo_fast_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
{
        qdisc->q.qlen++;
        return __qdisc_requeue(skb, qdisc, prio2list(skb, qdisc));
}

static void pfifo_fast_reset(struct Qdisc* qdisc)
{
        int prio;
        struct sk_buff_head *list = qdisc_priv(qdisc);

        for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
                __qdisc_reset_queue(qdisc, list + prio);

        qdisc->qstats.backlog = 0;
        qdisc->q.qlen = 0;
}

static int pfifo_fast_dump(struct Qdisc *qdisc, struct sk_buff *skb)
{
        struct tc_prio_qopt opt = { .bands = PFIFO_FAST_BANDS };

        memcpy(&opt.priomap, prio2band, TC_PRIO_MAX+1);
        NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
        return skb->len;

nla_put_failure:
        return -1;
}

static int pfifo_fast_init(struct Qdisc *qdisc, struct nlattr *opt)
{
        int prio;
        struct sk_buff_head *list = qdisc_priv(qdisc);

        for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
                skb_queue_head_init(list + prio);

        return 0;
}

static struct Qdisc_ops pfifo_fast_ops __read_mostly = {
        .id             =       "pfifo_fast",
        .priv_size      =       PFIFO_FAST_BANDS * sizeof(struct sk_buff_head),
        .enqueue        =       pfifo_fast_enqueue,
        .dequeue        =       pfifo_fast_dequeue,
        .requeue        =       pfifo_fast_requeue,
        .init           =       pfifo_fast_init,
        .reset          =       pfifo_fast_reset,
        .dump           =       pfifo_fast_dump,
        .owner          =       THIS_MODULE,
};

struct Qdisc *qdisc_alloc(struct net_device *dev, struct Qdisc_ops *ops)
{
        void *p;
        struct Qdisc *sch;
        unsigned int size;
        int err = -ENOBUFS;

        /* ensure that the Qdisc and the private data are 32-byte aligned */
        size = QDISC_ALIGN(sizeof(*sch));
        size += ops->priv_size + (QDISC_ALIGNTO - 1);

        p = kzalloc(size, GFP_KERNEL);
        if (!p)
                goto errout;
        sch = (struct Qdisc *) QDISC_ALIGN((unsigned long) p);
        sch->padded = (char *) sch - (char *) p;

        INIT_LIST_HEAD(&sch->list);
        skb_queue_head_init(&sch->q);
        sch->ops = ops;
        sch->enqueue = ops->enqueue;
        sch->dequeue = ops->dequeue;
        sch->dev = dev;
        dev_hold(dev);
        atomic_set(&sch->refcnt, 1);

        return sch;
errout:
        return ERR_PTR(-err);
}

struct Qdisc * qdisc_create_dflt(struct net_device *dev, struct Qdisc_ops *ops,
                                 unsigned int parentid)
{
        struct Qdisc *sch;

        sch = qdisc_alloc(dev, ops);
        if (IS_ERR(sch))
                goto errout;
        sch->stats_lock = &dev->queue_lock;
        sch->parent = parentid;

        if (!ops->init || ops->init(sch, NULL) == 0)
                return sch;

        qdisc_destroy(sch);
errout:
        return NULL;
}
EXPORT_SYMBOL(qdisc_create_dflt);

/* Under dev->queue_lock and BH! */

void qdisc_reset(struct Qdisc *qdisc)
{
        const struct Qdisc_ops *ops = qdisc->ops;

        if (ops->reset)
                ops->reset(qdisc);
}
EXPORT_SYMBOL(qdisc_reset);

/* this is the rcu callback function to clean up a qdisc when there
 * are no further references to it */

static void __qdisc_destroy(struct rcu_head *head)
{
        struct Qdisc *qdisc = container_of(head, struct Qdisc, q_rcu);
        kfree((char *) qdisc - qdisc->padded);
}

/* Under dev->queue_lock and BH! */

void qdisc_destroy(struct Qdisc *qdisc)
{
        const struct Qdisc_ops  *ops = qdisc->ops;

        if (qdisc->flags & TCQ_F_BUILTIN ||
            !atomic_dec_and_test(&qdisc->refcnt))
                return;

        list_del(&qdisc->list);
        gen_kill_estimator(&qdisc->bstats, &qdisc->rate_est);
        if (ops->reset)
                ops->reset(qdisc);
        if (ops->destroy)
                ops->destroy(qdisc);

        module_put(ops->owner);
        dev_put(qdisc->dev);
        call_rcu(&qdisc->q_rcu, __qdisc_destroy);
}
EXPORT_SYMBOL(qdisc_destroy);

void dev_activate(struct net_device *dev)
{
        /* No queueing discipline is attached to device;
           create default one i.e. pfifo_fast for devices,
           which need queueing and noqueue_qdisc for
           virtual interfaces
         */

        if (dev->qdisc_sleeping == &noop_qdisc) {
                struct Qdisc *qdisc;
                if (dev->tx_queue_len) {
                        qdisc = qdisc_create_dflt(dev, &pfifo_fast_ops,
                                                  TC_H_ROOT);
                        if (qdisc == NULL) {
                                printk(KERN_INFO "%s: activation failed\n", dev->name);
                                return;
                        }
                        list_add_tail(&qdisc->list, &dev->qdisc_list);
                } else {
                        qdisc =  &noqueue_qdisc;
                }
                dev->qdisc_sleeping = qdisc;
        }

        if (!netif_carrier_ok(dev))
                /* Delay activation until next carrier-on event */
                return;

        spin_lock_bh(&dev->queue_lock);
        rcu_assign_pointer(dev->qdisc, dev->qdisc_sleeping);
        if (dev->qdisc != &noqueue_qdisc) {
                dev->trans_start = jiffies;
                dev_watchdog_up(dev);
        }
        spin_unlock_bh(&dev->queue_lock);
}

void dev_deactivate(struct net_device *dev)
{
        struct Qdisc *qdisc;
        struct sk_buff *skb;
        int running;

        spin_lock_bh(&dev->queue_lock);
        qdisc = dev->qdisc;
        dev->qdisc = &noop_qdisc;

        qdisc_reset(qdisc);

        skb = dev->gso_skb;
        dev->gso_skb = NULL;
        spin_unlock_bh(&dev->queue_lock);

        kfree_skb(skb);

        dev_watchdog_down(dev);

        /* Wait for outstanding qdisc-less dev_queue_xmit calls. */
        synchronize_rcu();

        /* Wait for outstanding qdisc_run calls. */
        do {
                while (test_bit(__LINK_STATE_QDISC_RUNNING, &dev->state))
                        yield();

                /*
                 * Double-check inside queue lock to ensure that all effects
                 * of the queue run are visible when we return.
                 */
                spin_lock_bh(&dev->queue_lock);
                running = test_bit(__LINK_STATE_QDISC_RUNNING, &dev->state);
                spin_unlock_bh(&dev->queue_lock);

                /*
                 * The running flag should never be set at this point because
                 * we've already set dev->qdisc to noop_qdisc *inside* the same
                 * pair of spin locks.  That is, if any qdisc_run starts after
                 * our initial test it should see the noop_qdisc and then
                 * clear the RUNNING bit before dropping the queue lock.  So
                 * if it is set here then we've found a bug.
                 */
        } while (WARN_ON_ONCE(running));
}

void dev_init_scheduler(struct net_device *dev)
{
        qdisc_lock_tree(dev);
        dev->qdisc = &noop_qdisc;
        dev->qdisc_sleeping = &noop_qdisc;
        INIT_LIST_HEAD(&dev->qdisc_list);
        qdisc_unlock_tree(dev);

        setup_timer(&dev->watchdog_timer, dev_watchdog, (unsigned long)dev);
}

void dev_shutdown(struct net_device *dev)
{
        struct Qdisc *qdisc;

        qdisc_lock_tree(dev);
        qdisc = dev->qdisc_sleeping;
        dev->qdisc = &noop_qdisc;
        dev->qdisc_sleeping = &noop_qdisc;
        qdisc_destroy(qdisc);
#if defined(CONFIG_NET_SCH_INGRESS) || defined(CONFIG_NET_SCH_INGRESS_MODULE)
        if ((qdisc = dev->qdisc_ingress) != NULL) {
                dev->qdisc_ingress = NULL;
                qdisc_destroy(qdisc);
        }
#endif
        BUG_TRAP(!timer_pending(&dev->watchdog_timer));
        qdisc_unlock_tree(dev);
}