drivers/char/drm/lock.c

   1 /* lock.c -- IOCTLs for locking -*- linux-c -*-
   2  * Created: Tue Feb  2 08:37:54 1999 by faith@precisioninsight.com
   3  *
   4  * Copyright 1999 Precision Insight, Inc., Cedar Park, Texas.
   5  * Copyright 2000 VA Linux Systems, Inc., Sunnyvale, California.
   6  * All Rights Reserved.
   7  *
   8  * Permission is hereby granted, free of charge, to any person obtaining a
   9  * copy of this software and associated documentation files (the "Software"),
  10  * to deal in the Software without restriction, including without limitation
  11  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  12  * and/or sell copies of the Software, and to permit persons to whom the
  13  * Software is furnished to do so, subject to the following conditions:
  14  *
  15  * The above copyright notice and this permission notice (including the next
  16  * paragraph) shall be included in all copies or substantial portions of the
  17  * Software.
  18  *
  19  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  20  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  21  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  22  * PRECISION INSIGHT AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
  23  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  24  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  25  * DEALINGS IN THE SOFTWARE.
  26  *
  27  * Authors:
  28  *    Rickard E. (Rik) Faith <faith@valinux.com>
  29  *
  30  */
  31
  32 #define __NO_VERSION__
  33 #include "drmP.h"
  34
  35 int drm_block(struct inode *inode, struct file *filp, unsigned int cmd,
  36               unsigned long arg)
  37 {
  38         DRM_DEBUG("\n");
  39         return 0;
  40 }
  41
  42 int drm_unblock(struct inode *inode, struct file *filp, unsigned int cmd,
  43                 unsigned long arg)
  44 {
  45         DRM_DEBUG("\n");
  46         return 0;
  47 }
  48
  49 int drm_lock_take(__volatile__ unsigned int *lock, unsigned int context)
  50 {
  51         unsigned int old, new, prev;
  52
  53         DRM_DEBUG("%d attempts\n", context);
  54         do {
  55                 old = *lock;
  56                 if (old & _DRM_LOCK_HELD) new = old | _DRM_LOCK_CONT;
  57                 else                      new = context | _DRM_LOCK_HELD;
  58                 prev = cmpxchg(lock, old, new);
  59         } while (prev != old);
  60         if (_DRM_LOCKING_CONTEXT(old) == context) {
  61                 if (old & _DRM_LOCK_HELD) {
  62                         if (context != DRM_KERNEL_CONTEXT) {
  63                                 DRM_ERROR("%d holds heavyweight lock\n",
  64                                           context);
  65                         }
  66                         return 0;
  67                 }
  68         }
  69         if (new == (context | _DRM_LOCK_HELD)) {
  70                                 /* Have lock */
  71                 DRM_DEBUG("%d\n", context);
  72                 return 1;
  73         }
  74         DRM_DEBUG("%d unable to get lock held by %d\n",
  75                   context, _DRM_LOCKING_CONTEXT(old));
  76         return 0;
  77 }
  78
  79 /* This takes a lock forcibly and hands it to context.  Should ONLY be used
  80    inside *_unlock to give lock to kernel before calling *_dma_schedule. */
  81 int drm_lock_transfer(drm_device_t *dev,
  82                       __volatile__ unsigned int *lock, unsigned int context)
  83 {
  84         unsigned int old, new, prev;
  85
  86         dev->lock.pid = 0;
  87         do {
  88                 old  = *lock;
  89                 new  = context | _DRM_LOCK_HELD;
  90                 prev = cmpxchg(lock, old, new);
  91         } while (prev != old);
  92         DRM_DEBUG("%d => %d\n", _DRM_LOCKING_CONTEXT(old), context);
  93         return 1;
  94 }
  95
  96 int drm_lock_free(drm_device_t *dev,
  97                   __volatile__ unsigned int *lock, unsigned int context)
  98 {
  99         unsigned int old, new, prev;
 100         pid_t        pid = dev->lock.pid;
 101
 102         DRM_DEBUG("%d\n", context);
 103         dev->lock.pid = 0;
 104         do {
 105                 old  = *lock;
 106                 new  = 0;
 107                 prev = cmpxchg(lock, old, new);
 108         } while (prev != old);
 109         if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
 110                 DRM_ERROR("%d freed heavyweight lock held by %d (pid %d)\n",
 111                           context,
 112                           _DRM_LOCKING_CONTEXT(old),
 113                           pid);
 114                 return 1;
 115         }
 116         wake_up_interruptible(&dev->lock.lock_queue);
 117         return 0;
 118 }
 119
 120 static int drm_flush_queue(drm_device_t *dev, int context)
 121 {
 122         DECLARE_WAITQUEUE(entry, current);
 123         int               ret   = 0;
 124         drm_queue_t       *q    = dev->queuelist[context];
 125
 126         DRM_DEBUG("\n");
 127
 128         atomic_inc(&q->use_count);
 129         if (atomic_read(&q->use_count) > 1) {
 130                 atomic_inc(&q->block_write);
 131                 current->state = TASK_INTERRUPTIBLE;
 132                 add_wait_queue(&q->flush_queue, &entry);
 133                 atomic_inc(&q->block_count);
 134                 for (;;) {
 135                         if (!DRM_BUFCOUNT(&q->waitlist)) break;
 136                         schedule();
 137                         if (signal_pending(current)) {
 138                                 ret = -EINTR; /* Can't restart */
 139                                 break;
 140                         }
 141                 }
 142                 atomic_dec(&q->block_count);
 143                 current->state = TASK_RUNNING;
 144                 remove_wait_queue(&q->flush_queue, &entry);
 145         }
 146         atomic_dec(&q->use_count);
 147         atomic_inc(&q->total_flushed);
 148
 149                                 /* NOTE: block_write is still incremented!
 150                                    Use drm_flush_unlock_queue to decrement. */
 151         return ret;
 152 }
 153
 154 static int drm_flush_unblock_queue(drm_device_t *dev, int context)
 155 {
 156         drm_queue_t       *q    = dev->queuelist[context];
 157
 158         DRM_DEBUG("\n");
 159
 160         atomic_inc(&q->use_count);
 161         if (atomic_read(&q->use_count) > 1) {
 162                 if (atomic_read(&q->block_write)) {
 163                         atomic_dec(&q->block_write);
 164                         wake_up_interruptible(&q->write_queue);
 165                 }
 166         }
 167         atomic_dec(&q->use_count);
 168         return 0;
 169 }
 170
 171 int drm_flush_block_and_flush(drm_device_t *dev, int context,
 172                               drm_lock_flags_t flags)
 173 {
 174         int ret = 0;
 175         int i;
 176
 177         DRM_DEBUG("\n");
 178
 179         if (flags & _DRM_LOCK_FLUSH) {
 180                 ret = drm_flush_queue(dev, DRM_KERNEL_CONTEXT);
 181                 if (!ret) ret = drm_flush_queue(dev, context);
 182         }
 183         if (flags & _DRM_LOCK_FLUSH_ALL) {
 184                 for (i = 0; !ret && i < dev->queue_count; i++) {
 185                         ret = drm_flush_queue(dev, i);
 186                 }
 187         }
 188         return ret;
 189 }
 190
 191 int drm_flush_unblock(drm_device_t *dev, int context, drm_lock_flags_t flags)
 192 {
 193         int ret = 0;
 194         int i;
 195
 196         DRM_DEBUG("\n");
 197
 198         if (flags & _DRM_LOCK_FLUSH) {
 199                 ret = drm_flush_unblock_queue(dev, DRM_KERNEL_CONTEXT);
 200                 if (!ret) ret = drm_flush_unblock_queue(dev, context);
 201         }
 202         if (flags & _DRM_LOCK_FLUSH_ALL) {
 203                 for (i = 0; !ret && i < dev->queue_count; i++) {
 204                         ret = drm_flush_unblock_queue(dev, i);
 205                 }
 206         }
 207
 208         return ret;
 209 }
 210
 211 int drm_finish(struct inode *inode, struct file *filp, unsigned int cmd,
 212                unsigned long arg)
 213 {
 214         drm_file_t        *priv   = filp->private_data;
 215         drm_device_t      *dev    = priv->dev;
 216         int               ret     = 0;
 217         drm_lock_t        lock;
 218
 219         DRM_DEBUG("\n");
 220
 221         if (copy_from_user(&lock, (drm_lock_t *)arg, sizeof(lock)))
 222                 return -EFAULT;
 223         ret = drm_flush_block_and_flush(dev, lock.context, lock.flags);
 224         drm_flush_unblock(dev, lock.context, lock.flags);
 225         return ret;
 226 }
 227
 228 /* If we get here, it means that the process has called DRM_IOCTL_LOCK
 229    without calling DRM_IOCTL_UNLOCK.
 230
 231    If the lock is not held, then let the signal proceed as usual.
 232
 233    If the lock is held, then set the contended flag and keep the signal
 234    blocked.
 235
 236
 237    Return 1 if the signal should be delivered normally.
 238    Return 0 if the signal should be blocked.  */
 239
 240 int drm_notifier(void *priv)
 241 {
 242         drm_sigdata_t *s = (drm_sigdata_t *)priv;
 243         unsigned int  old, new, prev;
 244
 245
 246                                 /* Allow signal delivery if lock isn't held */
 247         if (!_DRM_LOCK_IS_HELD(s->lock->lock)
 248             || _DRM_LOCKING_CONTEXT(s->lock->lock) != s->context) return 1;
 249
 250                                 /* Otherwise, set flag to force call to
 251                                    drmUnlock */
 252         do {
 253                 old  = s->lock->lock;
 254                 new  = old | _DRM_LOCK_CONT;
 255                 prev = cmpxchg(&s->lock->lock, old, new);
 256         } while (prev != old);
 257         return 0;
 258 }