drivers/connector/cn_queue.c

   1 /*
   2  *      cn_queue.c
   3  *
   4  * 2004+ Copyright (c) Evgeniy Polyakov <zbr@ioremap.net>
   5  * All rights reserved.
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  20  *
  21  */
  22
  23 #include <linux/kernel.h>
  24 #include <linux/module.h>
  25 #include <linux/list.h>
  26 #include <linux/workqueue.h>
  27 #include <linux/spinlock.h>
  28 #include <linux/slab.h>
  29 #include <linux/skbuff.h>
  30 #include <linux/suspend.h>
  31 #include <linux/connector.h>
  32 #include <linux/delay.h>
  33
  34
  35 /*
  36  * This job is sent to the kevent workqueue.
  37  * While no event is once sent to any callback, the connector workqueue
  38  * is not created to avoid a useless waiting kernel task.
  39  * Once the first event is received, we create this dedicated workqueue which
  40  * is necessary because the flow of data can be high and we don't want
  41  * to encumber keventd with that.
  42  */
  43 static void cn_queue_create(struct work_struct *work)
  44 {
  45         struct cn_queue_dev *dev;
  46
  47         dev = container_of(work, struct cn_queue_dev, wq_creation);
  48
  49         dev->cn_queue = create_singlethread_workqueue(dev->name);
  50         /* If we fail, we will use keventd for all following connector jobs */
  51         WARN_ON(!dev->cn_queue);
  52 }
  53
  54 /*
  55  * Queue a data sent to a callback.
  56  * If the connector workqueue is already created, we queue the job on it.
  57  * Otherwise, we queue the job to kevent and queue the connector workqueue
  58  * creation too.
  59  */
  60 int queue_cn_work(struct cn_callback_entry *cbq, struct work_struct *work)
  61 {
  62         struct cn_queue_dev *pdev = cbq->pdev;
  63
  64         if (likely(pdev->cn_queue))
  65                 return queue_work(pdev->cn_queue, work);
  66
  67         /* Don't create the connector workqueue twice */
  68         if (atomic_inc_return(&pdev->wq_requested) == 1)
  69                 schedule_work(&pdev->wq_creation);
  70         else
  71                 atomic_dec(&pdev->wq_requested);
  72
  73         return schedule_work(work);
  74 }
  75
  76 void cn_queue_wrapper(struct work_struct *work)
  77 {
  78         struct cn_callback_entry *cbq =
  79                 container_of(work, struct cn_callback_entry, work);
  80         struct cn_callback_data *d = &cbq->data;
  81         struct cn_msg *msg = NLMSG_DATA(nlmsg_hdr(d->skb));
  82         struct netlink_skb_parms *nsp = &NETLINK_CB(d->skb);
  83
  84         d->callback(msg, nsp);
  85
  86         kfree_skb(d->skb);
  87         d->skb = NULL;
  88
  89         kfree(d->free);
  90 }
  91
  92 static struct cn_callback_entry *
  93 cn_queue_alloc_callback_entry(char *name, struct cb_id *id,
  94                               void (*callback)(struct cn_msg *, struct netlink_skb_parms *))
  95 {
  96         struct cn_callback_entry *cbq;
  97
  98         cbq = kzalloc(sizeof(*cbq), GFP_KERNEL);
  99         if (!cbq) {
 100                 printk(KERN_ERR "Failed to create new callback queue.\n");
 101                 return NULL;
 102         }
 103
 104         snprintf(cbq->id.name, sizeof(cbq->id.name), "%s", name);
 105         memcpy(&cbq->id.id, id, sizeof(struct cb_id));
 106         cbq->data.callback = callback;
 107
 108         INIT_WORK(&cbq->work, &cn_queue_wrapper);
 109         return cbq;
 110 }
 111
 112 static void cn_queue_free_callback(struct cn_callback_entry *cbq)
 113 {
 114         /* The first jobs have been sent to kevent, flush them too */
 115         flush_scheduled_work();
 116         if (cbq->pdev->cn_queue)
 117                 flush_workqueue(cbq->pdev->cn_queue);
 118
 119         kfree(cbq);
 120 }
 121
 122 int cn_cb_equal(struct cb_id *i1, struct cb_id *i2)
 123 {
 124         return ((i1->idx == i2->idx) && (i1->val == i2->val));
 125 }
 126
 127 int cn_queue_add_callback(struct cn_queue_dev *dev, char *name, struct cb_id *id,
 128                           void (*callback)(struct cn_msg *, struct netlink_skb_parms *))
 129 {
 130         struct cn_callback_entry *cbq, *__cbq;
 131         int found = 0;
 132
 133         cbq = cn_queue_alloc_callback_entry(name, id, callback);
 134         if (!cbq)
 135                 return -ENOMEM;
 136
 137         atomic_inc(&dev->refcnt);
 138         cbq->pdev = dev;
 139
 140         spin_lock_bh(&dev->queue_lock);
 141         list_for_each_entry(__cbq, &dev->queue_list, callback_entry) {
 142                 if (cn_cb_equal(&__cbq->id.id, id)) {
 143                         found = 1;
 144                         break;
 145                 }
 146         }
 147         if (!found)
 148                 list_add_tail(&cbq->callback_entry, &dev->queue_list);
 149         spin_unlock_bh(&dev->queue_lock);
 150
 151         if (found) {
 152                 cn_queue_free_callback(cbq);
 153                 atomic_dec(&dev->refcnt);
 154                 return -EINVAL;
 155         }
 156
 157         cbq->seq = 0;
 158         cbq->group = cbq->id.id.idx;
 159
 160         return 0;
 161 }
 162
 163 void cn_queue_del_callback(struct cn_queue_dev *dev, struct cb_id *id)
 164 {
 165         struct cn_callback_entry *cbq, *n;
 166         int found = 0;
 167
 168         spin_lock_bh(&dev->queue_lock);
 169         list_for_each_entry_safe(cbq, n, &dev->queue_list, callback_entry) {
 170                 if (cn_cb_equal(&cbq->id.id, id)) {
 171                         list_del(&cbq->callback_entry);
 172                         found = 1;
 173                         break;
 174                 }
 175         }
 176         spin_unlock_bh(&dev->queue_lock);
 177
 178         if (found) {
 179                 cn_queue_free_callback(cbq);
 180                 atomic_dec(&dev->refcnt);
 181         }
 182 }
 183
 184 struct cn_queue_dev *cn_queue_alloc_dev(char *name, struct sock *nls)
 185 {
 186         struct cn_queue_dev *dev;
 187
 188         dev = kzalloc(sizeof(*dev), GFP_KERNEL);
 189         if (!dev)
 190                 return NULL;
 191
 192         snprintf(dev->name, sizeof(dev->name), "%s", name);
 193         atomic_set(&dev->refcnt, 0);
 194         INIT_LIST_HEAD(&dev->queue_list);
 195         spin_lock_init(&dev->queue_lock);
 196         init_waitqueue_head(&dev->wq_created);
 197
 198         dev->nls = nls;
 199
 200         INIT_WORK(&dev->wq_creation, cn_queue_create);
 201
 202         return dev;
 203 }
 204
 205 void cn_queue_free_dev(struct cn_queue_dev *dev)
 206 {
 207         struct cn_callback_entry *cbq, *n;
 208         long timeout;
 209         DEFINE_WAIT(wait);
 210
 211         /* Flush the first pending jobs queued on kevent */
 212         flush_scheduled_work();
 213
 214         /* If the connector workqueue creation is still pending, wait for it */
 215         prepare_to_wait(&dev->wq_created, &wait, TASK_UNINTERRUPTIBLE);
 216         if (atomic_read(&dev->wq_requested) && !dev->cn_queue) {
 217                 timeout = schedule_timeout(HZ * 2);
 218                 if (!timeout && !dev->cn_queue)
 219                         WARN_ON(1);
 220         }
 221         finish_wait(&dev->wq_created, &wait);
 222
 223         if (dev->cn_queue) {
 224                 flush_workqueue(dev->cn_queue);
 225                 destroy_workqueue(dev->cn_queue);
 226         }
 227
 228         spin_lock_bh(&dev->queue_lock);
 229         list_for_each_entry_safe(cbq, n, &dev->queue_list, callback_entry)
 230                 list_del(&cbq->callback_entry);
 231         spin_unlock_bh(&dev->queue_lock);
 232
 233         while (atomic_read(&dev->refcnt)) {
 234                 printk(KERN_INFO "Waiting for %s to become free: refcnt=%d.\n",
 235                        dev->name, atomic_read(&dev->refcnt));
 236                 msleep(1000);
 237         }
 238
 239         kfree(dev);
 240         dev = NULL;
 241 }