drivers/char/drm/drm_lock.c

   1 /**
   2  * \file drm_lock.c
   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, lock.context)) {
  91                         dev->lock.filp = filp;
  92                         dev->lock.lock_time = jiffies;
  93                         atomic_inc(&dev->counts[_DRM_STAT_LOCKS]);
  94                         break;  /* Got lock */
  95                 }
  96
  97                 /* Contention */
  98                 schedule();
  99                 if (signal_pending(current)) {
 100                         ret = -ERESTARTSYS;
 101                         break;
 102                 }
 103         }
 104         __set_current_state(TASK_RUNNING);
 105         remove_wait_queue(&dev->lock.lock_queue, &entry);
 106
 107         DRM_DEBUG("%d %s\n", lock.context, ret ? "interrupted" : "has lock");
 108         if (ret)
 109                 return ret;
 110
 111         sigemptyset(&dev->sigmask);
 112         sigaddset(&dev->sigmask, SIGSTOP);
 113         sigaddset(&dev->sigmask, SIGTSTP);
 114         sigaddset(&dev->sigmask, SIGTTIN);
 115         sigaddset(&dev->sigmask, SIGTTOU);
 116         dev->sigdata.context = lock.context;
 117         dev->sigdata.lock = dev->lock.hw_lock;
 118         block_all_signals(drm_notifier, &dev->sigdata, &dev->sigmask);
 119
 120         if (dev->driver->dma_ready && (lock.flags & _DRM_LOCK_READY))
 121                 dev->driver->dma_ready(dev);
 122
 123         if (dev->driver->dma_quiescent && (lock.flags & _DRM_LOCK_QUIESCENT)) {
 124                 if (dev->driver->dma_quiescent(dev)) {
 125                         DRM_DEBUG("%d waiting for DMA quiescent\n", lock.context);
 126                         return DRM_ERR(EBUSY);
 127                 }
 128         }
 129
 130         /* dev->driver->kernel_context_switch isn't used by any of the x86
 131          *  drivers but is used by the Sparc driver.
 132          */
 133         if (dev->driver->kernel_context_switch &&
 134             dev->last_context != lock.context) {
 135                 dev->driver->kernel_context_switch(dev, dev->last_context,
 136                                                    lock.context);
 137         }
 138         return 0;
 139 }
 140
 141 /**
 142  * Unlock ioctl.
 143  *
 144  * \param inode device inode.
 145  * \param filp file pointer.
 146  * \param cmd command.
 147  * \param arg user argument, pointing to a drm_lock structure.
 148  * \return zero on success or negative number on failure.
 149  *
 150  * Transfer and free the lock.
 151  */
 152 int drm_unlock(struct inode *inode, struct file *filp,
 153                unsigned int cmd, unsigned long arg)
 154 {
 155         drm_file_t *priv = filp->private_data;
 156         drm_device_t *dev = priv->head->dev;
 157         drm_lock_t lock;
 158
 159         if (copy_from_user(&lock, (drm_lock_t __user *) arg, sizeof(lock)))
 160                 return -EFAULT;
 161
 162         if (lock.context == DRM_KERNEL_CONTEXT) {
 163                 DRM_ERROR("Process %d using kernel context %d\n",
 164                           current->pid, lock.context);
 165                 return -EINVAL;
 166         }
 167
 168         atomic_inc(&dev->counts[_DRM_STAT_UNLOCKS]);
 169
 170         /* kernel_context_switch isn't used by any of the x86 drm
 171          * modules but is required by the Sparc driver.
 172          */
 173         if (dev->driver->kernel_context_switch_unlock)
 174                 dev->driver->kernel_context_switch_unlock(dev, &lock);
 175         else {
 176                 drm_lock_transfer(dev, &dev->lock.hw_lock->lock,
 177                                   DRM_KERNEL_CONTEXT);
 178
 179                 if (drm_lock_free(dev, &dev->lock.hw_lock->lock,
 180                                   DRM_KERNEL_CONTEXT)) {
 181                         DRM_ERROR("\n");
 182                 }
 183         }
 184
 185         unblock_all_signals();
 186         return 0;
 187 }
 188
 189 /**
 190  * Take the heavyweight lock.
 191  *
 192  * \param lock lock pointer.
 193  * \param context locking context.
 194  * \return one if the lock is held, or zero otherwise.
 195  *
 196  * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
 197  */
 198 int drm_lock_take(__volatile__ unsigned int *lock, unsigned int context)
 199 {
 200         unsigned int old, new, prev;
 201
 202         do {
 203                 old = *lock;
 204                 if (old & _DRM_LOCK_HELD)
 205                         new = old | _DRM_LOCK_CONT;
 206                 else
 207                         new = context | _DRM_LOCK_HELD;
 208                 prev = cmpxchg(lock, old, new);
 209         } while (prev != old);
 210         if (_DRM_LOCKING_CONTEXT(old) == context) {
 211                 if (old & _DRM_LOCK_HELD) {
 212                         if (context != DRM_KERNEL_CONTEXT) {
 213                                 DRM_ERROR("%d holds heavyweight lock\n",
 214                                           context);
 215                         }
 216                         return 0;
 217                 }
 218         }
 219         if (new == (context | _DRM_LOCK_HELD)) {
 220                 /* Have lock */
 221                 return 1;
 222         }
 223         return 0;
 224 }
 225
 226 /**
 227  * This takes a lock forcibly and hands it to context.  Should ONLY be used
 228  * inside *_unlock to give lock to kernel before calling *_dma_schedule.
 229  *
 230  * \param dev DRM device.
 231  * \param lock lock pointer.
 232  * \param context locking context.
 233  * \return always one.
 234  *
 235  * Resets the lock file pointer.
 236  * Marks the lock as held by the given context, via the \p cmpxchg instruction.
 237  */
 238 static int drm_lock_transfer(drm_device_t * dev,
 239                              __volatile__ unsigned int *lock,
 240                              unsigned int context)
 241 {
 242         unsigned int old, new, prev;
 243
 244         dev->lock.filp = NULL;
 245         do {
 246                 old = *lock;
 247                 new = context | _DRM_LOCK_HELD;
 248                 prev = cmpxchg(lock, old, new);
 249         } while (prev != old);
 250         return 1;
 251 }
 252
 253 /**
 254  * Free lock.
 255  *
 256  * \param dev DRM device.
 257  * \param lock lock.
 258  * \param context context.
 259  *
 260  * Resets the lock file pointer.
 261  * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
 262  * waiting on the lock queue.
 263  */
 264 int drm_lock_free(drm_device_t * dev,
 265                   __volatile__ unsigned int *lock, unsigned int context)
 266 {
 267         unsigned int old, new, prev;
 268
 269         dev->lock.filp = NULL;
 270         do {
 271                 old = *lock;
 272                 new = 0;
 273                 prev = cmpxchg(lock, old, new);
 274         } while (prev != old);
 275         if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
 276                 DRM_ERROR("%d freed heavyweight lock held by %d\n",
 277                           context, _DRM_LOCKING_CONTEXT(old));
 278                 return 1;
 279         }
 280         wake_up_interruptible(&dev->lock.lock_queue);
 281         return 0;
 282 }
 283
 284 /**
 285  * If we get here, it means that the process has called DRM_IOCTL_LOCK
 286  * without calling DRM_IOCTL_UNLOCK.
 287  *
 288  * If the lock is not held, then let the signal proceed as usual.  If the lock
 289  * is held, then set the contended flag and keep the signal blocked.
 290  *
 291  * \param priv pointer to a drm_sigdata structure.
 292  * \return one if the signal should be delivered normally, or zero if the
 293  * signal should be blocked.
 294  */
 295 static int drm_notifier(void *priv)
 296 {
 297         drm_sigdata_t *s = (drm_sigdata_t *) priv;
 298         unsigned int old, new, prev;
 299
 300         /* Allow signal delivery if lock isn't held */
 301         if (!s->lock || !_DRM_LOCK_IS_HELD(s->lock->lock)
 302             || _DRM_LOCKING_CONTEXT(s->lock->lock) != s->context)
 303                 return 1;
 304
 305         /* Otherwise, set flag to force call to
 306            drmUnlock */
 307         do {
 308                 old = s->lock->lock;
 309                 new = old | _DRM_LOCK_CONT;
 310                 prev = cmpxchg(&s->lock->lock, old, new);
 311         } while (prev != old);
 312         return 0;
 313 }