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 /**
  39  * Lock ioctl.
  40  *
  41  * \param inode device inode.
  42  * \param filp file pointer.
  43  * \param cmd command.
  44  * \param arg user argument, pointing to a drm_lock structure.
  45  * \return zero on success or negative number on failure.
  46  *
  47  * Add the current task to the lock wait queue, and attempt to take to lock.
  48  */
  49 int drm_lock( struct inode *inode, struct file *filp,
  50                unsigned int cmd, unsigned long arg )
  51 {
  52         drm_file_t *priv = filp->private_data;
  53         drm_device_t *dev = priv->head->dev;
  54         DECLARE_WAITQUEUE( entry, current );
  55         drm_lock_t lock;
  56         int ret = 0;
  57
  58         ++priv->lock_count;
  59
  60         if ( copy_from_user( &lock, (drm_lock_t __user *)arg, sizeof(lock) ) )
  61                 return -EFAULT;
  62
  63         if ( lock.context == DRM_KERNEL_CONTEXT ) {
  64                 DRM_ERROR( "Process %d using kernel context %d\n",
  65                            current->pid, lock.context );
  66                 return -EINVAL;
  67         }
  68
  69         DRM_DEBUG( "%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
  70                    lock.context, current->pid,
  71                    dev->lock.hw_lock->lock, lock.flags );
  72
  73         if (drm_core_check_feature(dev, DRIVER_DMA_QUEUE))
  74                 if ( lock.context < 0 )
  75                         return -EINVAL;
  76
  77         add_wait_queue( &dev->lock.lock_queue, &entry );
  78         for (;;) {
  79                 __set_current_state(TASK_INTERRUPTIBLE);
  80                 if ( !dev->lock.hw_lock ) {
  81                         /* Device has been unregistered */
  82                         ret = -EINTR;
  83                         break;
  84                 }
  85                 if ( drm_lock_take( &dev->lock.hw_lock->lock,
  86                                      lock.context ) ) {
  87                         dev->lock.filp      = filp;
  88                         dev->lock.lock_time = jiffies;
  89                         atomic_inc( &dev->counts[_DRM_STAT_LOCKS] );
  90                         break;  /* Got lock */
  91                 }
  92
  93                 /* Contention */
  94                 schedule();
  95                 if ( signal_pending( current ) ) {
  96                         ret = -ERESTARTSYS;
  97                         break;
  98                 }
  99         }
 100         __set_current_state(TASK_RUNNING);
 101         remove_wait_queue( &dev->lock.lock_queue, &entry );
 102
 103         sigemptyset( &dev->sigmask );
 104         sigaddset( &dev->sigmask, SIGSTOP );
 105         sigaddset( &dev->sigmask, SIGTSTP );
 106         sigaddset( &dev->sigmask, SIGTTIN );
 107         sigaddset( &dev->sigmask, SIGTTOU );
 108         dev->sigdata.context = lock.context;
 109         dev->sigdata.lock    = dev->lock.hw_lock;
 110         block_all_signals( drm_notifier,
 111                            &dev->sigdata, &dev->sigmask );
 112
 113         if (dev->driver->dma_ready && (lock.flags & _DRM_LOCK_READY))
 114                 dev->driver->dma_ready(dev);
 115
 116         if ( dev->driver->dma_quiescent && (lock.flags & _DRM_LOCK_QUIESCENT ))
 117                 return dev->driver->dma_quiescent(dev);
 118
 119         /* dev->driver->kernel_context_switch isn't used by any of the x86
 120          *  drivers but is used by the Sparc driver.
 121          */
 122
 123         if (dev->driver->kernel_context_switch &&
 124             dev->last_context != lock.context) {
 125           dev->driver->kernel_context_switch(dev, dev->last_context,
 126                                             lock.context);
 127         }
 128         DRM_DEBUG( "%d %s\n", lock.context, ret ? "interrupted" : "has lock" );
 129
 130         return ret;
 131 }
 132
 133 /**
 134  * Unlock ioctl.
 135  *
 136  * \param inode device inode.
 137  * \param filp file pointer.
 138  * \param cmd command.
 139  * \param arg user argument, pointing to a drm_lock structure.
 140  * \return zero on success or negative number on failure.
 141  *
 142  * Transfer and free the lock.
 143  */
 144 int drm_unlock( struct inode *inode, struct file *filp,
 145                  unsigned int cmd, unsigned long arg )
 146 {
 147         drm_file_t *priv = filp->private_data;
 148         drm_device_t *dev = priv->head->dev;
 149         drm_lock_t lock;
 150
 151         if ( copy_from_user( &lock, (drm_lock_t __user *)arg, sizeof(lock) ) )
 152                 return -EFAULT;
 153
 154         if ( lock.context == DRM_KERNEL_CONTEXT ) {
 155                 DRM_ERROR( "Process %d using kernel context %d\n",
 156                            current->pid, lock.context );
 157                 return -EINVAL;
 158         }
 159
 160         atomic_inc( &dev->counts[_DRM_STAT_UNLOCKS] );
 161
 162         /* kernel_context_switch isn't used by any of the x86 drm
 163          * modules but is required by the Sparc driver.
 164          */
 165         if (dev->driver->kernel_context_switch_unlock)
 166                 dev->driver->kernel_context_switch_unlock(dev, &lock);
 167         else {
 168                 drm_lock_transfer( dev, &dev->lock.hw_lock->lock,
 169                                     DRM_KERNEL_CONTEXT );
 170
 171                 if ( drm_lock_free( dev, &dev->lock.hw_lock->lock,
 172                                      DRM_KERNEL_CONTEXT ) ) {
 173                         DRM_ERROR( "\n" );
 174                 }
 175         }
 176
 177         unblock_all_signals();
 178         return 0;
 179 }
 180
 181 /**
 182  * Take the heavyweight lock.
 183  *
 184  * \param lock lock pointer.
 185  * \param context locking context.
 186  * \return one if the lock is held, or zero otherwise.
 187  *
 188  * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
 189  */
 190 int drm_lock_take(__volatile__ unsigned int *lock, unsigned int context)
 191 {
 192         unsigned int old, new, prev;
 193
 194         do {
 195                 old = *lock;
 196                 if (old & _DRM_LOCK_HELD) new = old | _DRM_LOCK_CONT;
 197                 else                      new = context | _DRM_LOCK_HELD;
 198                 prev = cmpxchg(lock, old, new);
 199         } while (prev != old);
 200         if (_DRM_LOCKING_CONTEXT(old) == context) {
 201                 if (old & _DRM_LOCK_HELD) {
 202                         if (context != DRM_KERNEL_CONTEXT) {
 203                                 DRM_ERROR("%d holds heavyweight lock\n",
 204                                           context);
 205                         }
 206                         return 0;
 207                 }
 208         }
 209         if (new == (context | _DRM_LOCK_HELD)) {
 210                                 /* Have lock */
 211                 return 1;
 212         }
 213         return 0;
 214 }
 215
 216 /**
 217  * This takes a lock forcibly and hands it to context.  Should ONLY be used
 218  * inside *_unlock to give lock to kernel before calling *_dma_schedule.
 219  *
 220  * \param dev DRM device.
 221  * \param lock lock pointer.
 222  * \param context locking context.
 223  * \return always one.
 224  *
 225  * Resets the lock file pointer.
 226  * Marks the lock as held by the given context, via the \p cmpxchg instruction.
 227  */
 228 int drm_lock_transfer(drm_device_t *dev,
 229                        __volatile__ unsigned int *lock, unsigned int context)
 230 {
 231         unsigned int old, new, prev;
 232
 233         dev->lock.filp = NULL;
 234         do {
 235                 old  = *lock;
 236                 new  = context | _DRM_LOCK_HELD;
 237                 prev = cmpxchg(lock, old, new);
 238         } while (prev != old);
 239         return 1;
 240 }
 241
 242 /**
 243  * Free lock.
 244  *
 245  * \param dev DRM device.
 246  * \param lock lock.
 247  * \param context context.
 248  *
 249  * Resets the lock file pointer.
 250  * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
 251  * waiting on the lock queue.
 252  */
 253 int drm_lock_free(drm_device_t *dev,
 254                    __volatile__ unsigned int *lock, unsigned int context)
 255 {
 256         unsigned int old, new, prev;
 257
 258         dev->lock.filp = NULL;
 259         do {
 260                 old  = *lock;
 261                 new  = 0;
 262                 prev = cmpxchg(lock, old, new);
 263         } while (prev != old);
 264         if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
 265                 DRM_ERROR("%d freed heavyweight lock held by %d\n",
 266                           context,
 267                           _DRM_LOCKING_CONTEXT(old));
 268                 return 1;
 269         }
 270         wake_up_interruptible(&dev->lock.lock_queue);
 271         return 0;
 272 }
 273
 274 /**
 275  * If we get here, it means that the process has called DRM_IOCTL_LOCK
 276  * without calling DRM_IOCTL_UNLOCK.
 277  *
 278  * If the lock is not held, then let the signal proceed as usual.  If the lock
 279  * is held, then set the contended flag and keep the signal blocked.
 280  *
 281  * \param priv pointer to a drm_sigdata structure.
 282  * \return one if the signal should be delivered normally, or zero if the
 283  * signal should be blocked.
 284  */
 285 int drm_notifier(void *priv)
 286 {
 287         drm_sigdata_t *s = (drm_sigdata_t *)priv;
 288         unsigned int  old, new, prev;
 289
 290
 291                                 /* Allow signal delivery if lock isn't held */
 292         if (!s->lock || !_DRM_LOCK_IS_HELD(s->lock->lock)
 293             || _DRM_LOCKING_CONTEXT(s->lock->lock) != s->context) return 1;
 294
 295                                 /* Otherwise, set flag to force call to
 296                                    drmUnlock */
 297         do {
 298                 old  = s->lock->lock;
 299                 new  = old | _DRM_LOCK_CONT;
 300                 prev = cmpxchg(&s->lock->lock, old, new);
 301         } while (prev != old);
 302         return 0;
 303 }