drivers/char/drm/drm_lock.c

   1 /**
   2  * \file drm_lock.h
   3  * IOCTLs for locking
   4  *
   5  * \author Rickard E. (Rik) Faith <faith@valinux.com>
   6  * \author Gareth Hughes <gareth@valinux.com>
   7  */
   8
   9 /*
  10  * Created: Tue Feb  2 08:37:54 1999 by faith@valinux.com
  11  *
  12  * Copyright 1999 Precision Insight, Inc., Cedar Park, Texas.
  13  * Copyright 2000 VA Linux Systems, Inc., Sunnyvale, California.
  14  * All Rights Reserved.
  15  *
  16  * Permission is hereby granted, free of charge, to any person obtaining a
  17  * copy of this software and associated documentation files (the "Software"),
  18  * to deal in the Software without restriction, including without limitation
  19  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  20  * and/or sell copies of the Software, and to permit persons to whom the
  21  * Software is furnished to do so, subject to the following conditions:
  22  *
  23  * The above copyright notice and this permission notice (including the next
  24  * paragraph) shall be included in all copies or substantial portions of the
  25  * Software.
  26  *
  27  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  28  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  29  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  30  * VA LINUX SYSTEMS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
  31  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  32  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  33  * OTHER DEALINGS IN THE SOFTWARE.
  34  */
  35
  36 #include "drmP.h"
  37
  38 static int drm_lock_transfer(drm_device_t *dev,
  39                              __volatile__ unsigned int *lock,
  40                              unsigned int context);
  41 static int drm_notifier(void *priv);
  42
  43 /**
  44  * Lock ioctl.
  45  *
  46  * \param inode device inode.
  47  * \param filp file pointer.
  48  * \param cmd command.
  49  * \param arg user argument, pointing to a drm_lock structure.
  50  * \return zero on success or negative number on failure.
  51  *
  52  * Add the current task to the lock wait queue, and attempt to take to lock.
  53  */
  54 int drm_lock( struct inode *inode, struct file *filp,
  55                unsigned int cmd, unsigned long arg )
  56 {
  57         drm_file_t *priv = filp->private_data;
  58         drm_device_t *dev = priv->head->dev;
  59         DECLARE_WAITQUEUE( entry, current );
  60         drm_lock_t lock;
  61         int ret = 0;
  62
  63         ++priv->lock_count;
  64
  65         if ( copy_from_user( &lock, (drm_lock_t __user *)arg, sizeof(lock) ) )
  66                 return -EFAULT;
  67
  68         if ( lock.context == DRM_KERNEL_CONTEXT ) {
  69                 DRM_ERROR( "Process %d using kernel context %d\n",
  70                            current->pid, lock.context );
  71                 return -EINVAL;
  72         }
  73
  74         DRM_DEBUG( "%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
  75                    lock.context, current->pid,
  76                    dev->lock.hw_lock->lock, lock.flags );
  77
  78         if (drm_core_check_feature(dev, DRIVER_DMA_QUEUE))
  79                 if ( lock.context < 0 )
  80                         return -EINVAL;
  81
  82         add_wait_queue( &dev->lock.lock_queue, &entry );
  83         for (;;) {
  84                 __set_current_state(TASK_INTERRUPTIBLE);
  85                 if ( !dev->lock.hw_lock ) {
  86                         /* Device has been unregistered */
  87                         ret = -EINTR;
  88                         break;
  89                 }
  90                 if ( drm_lock_take( &dev->lock.hw_lock->lock,
  91                                      lock.context ) ) {
  92                         dev->lock.filp      = filp;
  93                         dev->lock.lock_time = jiffies;
  94                         atomic_inc( &dev->counts[_DRM_STAT_LOCKS] );
  95                         break;  /* Got lock */
  96                 }
  97
  98                 /* Contention */
  99                 schedule();
 100                 if ( signal_pending( current ) ) {
 101                         ret = -ERESTARTSYS;
 102                         break;
 103                 }
 104         }
 105         __set_current_state(TASK_RUNNING);
 106         remove_wait_queue( &dev->lock.lock_queue, &entry );
 107
 108         sigemptyset( &dev->sigmask );
 109         sigaddset( &dev->sigmask, SIGSTOP );
 110         sigaddset( &dev->sigmask, SIGTSTP );
 111         sigaddset( &dev->sigmask, SIGTTIN );
 112         sigaddset( &dev->sigmask, SIGTTOU );
 113         dev->sigdata.context = lock.context;
 114         dev->sigdata.lock    = dev->lock.hw_lock;
 115         block_all_signals( drm_notifier,
 116                            &dev->sigdata, &dev->sigmask );
 117
 118         if (dev->driver->dma_ready && (lock.flags & _DRM_LOCK_READY))
 119                 dev->driver->dma_ready(dev);
 120
 121         if ( dev->driver->dma_quiescent && (lock.flags & _DRM_LOCK_QUIESCENT ))
 122                 return dev->driver->dma_quiescent(dev);
 123
 124         /* dev->driver->kernel_context_switch isn't used by any of the x86
 125          *  drivers but is used by the Sparc driver.
 126          */
 127
 128         if (dev->driver->kernel_context_switch &&
 129             dev->last_context != lock.context) {
 130           dev->driver->kernel_context_switch(dev, dev->last_context,
 131                                             lock.context);
 132         }
 133         DRM_DEBUG( "%d %s\n", lock.context, ret ? "interrupted" : "has lock" );
 134
 135         return ret;
 136 }
 137
 138 /**
 139  * Unlock ioctl.
 140  *
 141  * \param inode device inode.
 142  * \param filp file pointer.
 143  * \param cmd command.
 144  * \param arg user argument, pointing to a drm_lock structure.
 145  * \return zero on success or negative number on failure.
 146  *
 147  * Transfer and free the lock.
 148  */
 149 int drm_unlock( struct inode *inode, struct file *filp,
 150                  unsigned int cmd, unsigned long arg )
 151 {
 152         drm_file_t *priv = filp->private_data;
 153         drm_device_t *dev = priv->head->dev;
 154         drm_lock_t lock;
 155
 156         if ( copy_from_user( &lock, (drm_lock_t __user *)arg, sizeof(lock) ) )
 157                 return -EFAULT;
 158
 159         if ( lock.context == DRM_KERNEL_CONTEXT ) {
 160                 DRM_ERROR( "Process %d using kernel context %d\n",
 161                            current->pid, lock.context );
 162                 return -EINVAL;
 163         }
 164
 165         atomic_inc( &dev->counts[_DRM_STAT_UNLOCKS] );
 166
 167         /* kernel_context_switch isn't used by any of the x86 drm
 168          * modules but is required by the Sparc driver.
 169          */
 170         if (dev->driver->kernel_context_switch_unlock)
 171                 dev->driver->kernel_context_switch_unlock(dev, &lock);
 172         else {
 173                 drm_lock_transfer( dev, &dev->lock.hw_lock->lock,
 174                                     DRM_KERNEL_CONTEXT );
 175
 176                 if ( drm_lock_free( dev, &dev->lock.hw_lock->lock,
 177                                      DRM_KERNEL_CONTEXT ) ) {
 178                         DRM_ERROR( "\n" );
 179                 }
 180         }
 181
 182         unblock_all_signals();
 183         return 0;
 184 }
 185
 186 /**
 187  * Take the heavyweight lock.
 188  *
 189  * \param lock lock pointer.
 190  * \param context locking context.
 191  * \return one if the lock is held, or zero otherwise.
 192  *
 193  * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
 194  */
 195 int drm_lock_take(__volatile__ unsigned int *lock, unsigned int context)
 196 {
 197         unsigned int old, new, prev;
 198
 199         do {
 200                 old = *lock;
 201                 if (old & _DRM_LOCK_HELD) new = old | _DRM_LOCK_CONT;
 202                 else                      new = context | _DRM_LOCK_HELD;
 203                 prev = cmpxchg(lock, old, new);
 204         } while (prev != old);
 205         if (_DRM_LOCKING_CONTEXT(old) == context) {
 206                 if (old & _DRM_LOCK_HELD) {
 207                         if (context != DRM_KERNEL_CONTEXT) {
 208                                 DRM_ERROR("%d holds heavyweight lock\n",
 209                                           context);
 210                         }
 211                         return 0;
 212                 }
 213         }
 214         if (new == (context | _DRM_LOCK_HELD)) {
 215                                 /* Have lock */
 216                 return 1;
 217         }
 218         return 0;
 219 }
 220
 221 /**
 222  * This takes a lock forcibly and hands it to context.  Should ONLY be used
 223  * inside *_unlock to give lock to kernel before calling *_dma_schedule.
 224  *
 225  * \param dev DRM device.
 226  * \param lock lock pointer.
 227  * \param context locking context.
 228  * \return always one.
 229  *
 230  * Resets the lock file pointer.
 231  * Marks the lock as held by the given context, via the \p cmpxchg instruction.
 232  */
 233 static int drm_lock_transfer(drm_device_t *dev,
 234                              __volatile__ unsigned int *lock,
 235                              unsigned int context)
 236 {
 237         unsigned int old, new, prev;
 238
 239         dev->lock.filp = NULL;
 240         do {
 241                 old  = *lock;
 242                 new  = context | _DRM_LOCK_HELD;
 243                 prev = cmpxchg(lock, old, new);
 244         } while (prev != old);
 245         return 1;
 246 }
 247
 248 /**
 249  * Free lock.
 250  *
 251  * \param dev DRM device.
 252  * \param lock lock.
 253  * \param context context.
 254  *
 255  * Resets the lock file pointer.
 256  * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
 257  * waiting on the lock queue.
 258  */
 259 int drm_lock_free(drm_device_t *dev,
 260                    __volatile__ unsigned int *lock, unsigned int context)
 261 {
 262         unsigned int old, new, prev;
 263
 264         dev->lock.filp = NULL;
 265         do {
 266                 old  = *lock;
 267                 new  = 0;
 268                 prev = cmpxchg(lock, old, new);
 269         } while (prev != old);
 270         if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
 271                 DRM_ERROR("%d freed heavyweight lock held by %d\n",
 272                           context,
 273                           _DRM_LOCKING_CONTEXT(old));
 274                 return 1;
 275         }
 276         wake_up_interruptible(&dev->lock.lock_queue);
 277         return 0;
 278 }
 279
 280 /**
 281  * If we get here, it means that the process has called DRM_IOCTL_LOCK
 282  * without calling DRM_IOCTL_UNLOCK.
 283  *
 284  * If the lock is not held, then let the signal proceed as usual.  If the lock
 285  * is held, then set the contended flag and keep the signal blocked.
 286  *
 287  * \param priv pointer to a drm_sigdata structure.
 288  * \return one if the signal should be delivered normally, or zero if the
 289  * signal should be blocked.
 290  */
 291 static int drm_notifier(void *priv)
 292 {
 293         drm_sigdata_t *s = (drm_sigdata_t *)priv;
 294         unsigned int  old, new, prev;
 295
 296
 297                                 /* Allow signal delivery if lock isn't held */
 298         if (!s->lock || !_DRM_LOCK_IS_HELD(s->lock->lock)
 299             || _DRM_LOCKING_CONTEXT(s->lock->lock) != s->context) return 1;
 300
 301                                 /* Otherwise, set flag to force call to
 302                                    drmUnlock */
 303         do {
 304                 old  = s->lock->lock;
 305                 new  = old | _DRM_LOCK_CONT;
 306                 prev = cmpxchg(&s->lock->lock, old, new);
 307         } while (prev != old);
 308         return 0;
 309 }