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_notifier(void *priv);
  39
  40 /**
  41  * Lock ioctl.
  42  *
  43  * \param inode device inode.
  44  * \param file_priv DRM file private.
  45  * \param cmd command.
  46  * \param arg user argument, pointing to a drm_lock structure.
  47  * \return zero on success or negative number on failure.
  48  *
  49  * Add the current task to the lock wait queue, and attempt to take to lock.
  50  */
  51 int drm_lock(struct inode *inode, struct drm_file *file_priv,
  52              unsigned int cmd, unsigned long arg)
  53 {
  54         struct drm_device *dev = file_priv->head->dev;
  55         DECLARE_WAITQUEUE(entry, current);
  56         struct drm_lock lock;
  57         int ret = 0;
  58
  59         ++file_priv->lock_count;
  60
  61         if (copy_from_user(&lock, (struct drm_lock __user *) arg, sizeof(lock)))
  62                 return -EFAULT;
  63
  64         if (lock.context == DRM_KERNEL_CONTEXT) {
  65                 DRM_ERROR("Process %d using kernel context %d\n",
  66                           current->pid, lock.context);
  67                 return -EINVAL;
  68         }
  69
  70         DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
  71                   lock.context, current->pid,
  72                   dev->lock.hw_lock->lock, lock.flags);
  73
  74         if (drm_core_check_feature(dev, DRIVER_DMA_QUEUE))
  75                 if (lock.context < 0)
  76                         return -EINVAL;
  77
  78         add_wait_queue(&dev->lock.lock_queue, &entry);
  79         spin_lock(&dev->lock.spinlock);
  80         dev->lock.user_waiters++;
  81         spin_unlock(&dev->lock.spinlock);
  82         for (;;) {
  83                 __set_current_state(TASK_INTERRUPTIBLE);
  84                 if (!dev->lock.hw_lock) {
  85                         /* Device has been unregistered */
  86                         ret = -EINTR;
  87                         break;
  88                 }
  89                 if (drm_lock_take(&dev->lock, lock.context)) {
  90                         dev->lock.file_priv = file_priv;
  91                         dev->lock.lock_time = jiffies;
  92                         atomic_inc(&dev->counts[_DRM_STAT_LOCKS]);
  93                         break;  /* Got lock */
  94                 }
  95
  96                 /* Contention */
  97                 schedule();
  98                 if (signal_pending(current)) {
  99                         ret = -ERESTARTSYS;
 100                         break;
 101                 }
 102         }
 103         spin_lock(&dev->lock.spinlock);
 104         dev->lock.user_waiters--;
 105         spin_unlock(&dev->lock.spinlock);
 106         __set_current_state(TASK_RUNNING);
 107         remove_wait_queue(&dev->lock.lock_queue, &entry);
 108
 109         DRM_DEBUG( "%d %s\n", lock.context, ret ? "interrupted" : "has lock" );
 110         if (ret) return ret;
 111
 112         sigemptyset(&dev->sigmask);
 113         sigaddset(&dev->sigmask, SIGSTOP);
 114         sigaddset(&dev->sigmask, SIGTSTP);
 115         sigaddset(&dev->sigmask, SIGTTIN);
 116         sigaddset(&dev->sigmask, SIGTTOU);
 117         dev->sigdata.context = lock.context;
 118         dev->sigdata.lock = dev->lock.hw_lock;
 119         block_all_signals(drm_notifier, &dev->sigdata, &dev->sigmask);
 120
 121         if (dev->driver->dma_ready && (lock.flags & _DRM_LOCK_READY))
 122                 dev->driver->dma_ready(dev);
 123
 124         if (dev->driver->dma_quiescent && (lock.flags & _DRM_LOCK_QUIESCENT)) {
 125                 if (dev->driver->dma_quiescent(dev)) {
 126                         DRM_DEBUG("%d waiting for DMA quiescent\n", lock.context);
 127                         return -EBUSY;
 128                 }
 129         }
 130
 131         if (dev->driver->kernel_context_switch &&
 132             dev->last_context != lock.context) {
 133                 dev->driver->kernel_context_switch(dev, dev->last_context,
 134                                                    lock.context);
 135         }
 136
 137         return 0;
 138 }
 139
 140 /**
 141  * Unlock ioctl.
 142  *
 143  * \param inode device inode.
 144  * \param file_priv DRM file private.
 145  * \param cmd command.
 146  * \param arg user argument, pointing to a drm_lock structure.
 147  * \return zero on success or negative number on failure.
 148  *
 149  * Transfer and free the lock.
 150  */
 151 int drm_unlock(struct inode *inode, struct drm_file *file_priv,
 152                unsigned int cmd, unsigned long arg)
 153 {
 154         struct drm_device *dev = file_priv->head->dev;
 155         struct drm_lock lock;
 156         unsigned long irqflags;
 157
 158         if (copy_from_user(&lock, (struct drm_lock __user *) arg, sizeof(lock)))
 159                 return -EFAULT;
 160
 161         if (lock.context == DRM_KERNEL_CONTEXT) {
 162                 DRM_ERROR("Process %d using kernel context %d\n",
 163                           current->pid, lock.context);
 164                 return -EINVAL;
 165         }
 166
 167         spin_lock_irqsave(&dev->tasklet_lock, irqflags);
 168
 169         if (dev->locked_tasklet_func) {
 170                 dev->locked_tasklet_func(dev);
 171
 172                 dev->locked_tasklet_func = NULL;
 173         }
 174
 175         spin_unlock_irqrestore(&dev->tasklet_lock, irqflags);
 176
 177         atomic_inc(&dev->counts[_DRM_STAT_UNLOCKS]);
 178
 179         /* kernel_context_switch isn't used by any of the x86 drm
 180          * modules but is required by the Sparc driver.
 181          */
 182         if (dev->driver->kernel_context_switch_unlock)
 183                 dev->driver->kernel_context_switch_unlock(dev);
 184         else {
 185                 if (drm_lock_free(&dev->lock,lock.context)) {
 186                         /* FIXME: Should really bail out here. */
 187                 }
 188         }
 189
 190         unblock_all_signals();
 191         return 0;
 192 }
 193
 194 /**
 195  * Take the heavyweight lock.
 196  *
 197  * \param lock lock pointer.
 198  * \param context locking context.
 199  * \return one if the lock is held, or zero otherwise.
 200  *
 201  * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
 202  */
 203 int drm_lock_take(struct drm_lock_data *lock_data,
 204                   unsigned int context)
 205 {
 206         unsigned int old, new, prev;
 207         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 208
 209         spin_lock(&lock_data->spinlock);
 210         do {
 211                 old = *lock;
 212                 if (old & _DRM_LOCK_HELD)
 213                         new = old | _DRM_LOCK_CONT;
 214                 else {
 215                         new = context | _DRM_LOCK_HELD |
 216                                 ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
 217                                  _DRM_LOCK_CONT : 0);
 218                 }
 219                 prev = cmpxchg(lock, old, new);
 220         } while (prev != old);
 221         spin_unlock(&lock_data->spinlock);
 222
 223         if (_DRM_LOCKING_CONTEXT(old) == context) {
 224                 if (old & _DRM_LOCK_HELD) {
 225                         if (context != DRM_KERNEL_CONTEXT) {
 226                                 DRM_ERROR("%d holds heavyweight lock\n",
 227                                           context);
 228                         }
 229                         return 0;
 230                 }
 231         }
 232
 233         if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) {
 234                 /* Have lock */
 235                 return 1;
 236         }
 237         return 0;
 238 }
 239
 240 /**
 241  * This takes a lock forcibly and hands it to context.  Should ONLY be used
 242  * inside *_unlock to give lock to kernel before calling *_dma_schedule.
 243  *
 244  * \param dev DRM device.
 245  * \param lock lock pointer.
 246  * \param context locking context.
 247  * \return always one.
 248  *
 249  * Resets the lock file pointer.
 250  * Marks the lock as held by the given context, via the \p cmpxchg instruction.
 251  */
 252 static int drm_lock_transfer(struct drm_lock_data *lock_data,
 253                              unsigned int context)
 254 {
 255         unsigned int old, new, prev;
 256         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 257
 258         lock_data->file_priv = NULL;
 259         do {
 260                 old = *lock;
 261                 new = context | _DRM_LOCK_HELD;
 262                 prev = cmpxchg(lock, old, new);
 263         } while (prev != old);
 264         return 1;
 265 }
 266
 267 /**
 268  * Free lock.
 269  *
 270  * \param dev DRM device.
 271  * \param lock lock.
 272  * \param context context.
 273  *
 274  * Resets the lock file pointer.
 275  * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
 276  * waiting on the lock queue.
 277  */
 278 int drm_lock_free(struct drm_lock_data *lock_data, unsigned int context)
 279 {
 280         unsigned int old, new, prev;
 281         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 282
 283         spin_lock(&lock_data->spinlock);
 284         if (lock_data->kernel_waiters != 0) {
 285                 drm_lock_transfer(lock_data, 0);
 286                 lock_data->idle_has_lock = 1;
 287                 spin_unlock(&lock_data->spinlock);
 288                 return 1;
 289         }
 290         spin_unlock(&lock_data->spinlock);
 291
 292         do {
 293                 old = *lock;
 294                 new = _DRM_LOCKING_CONTEXT(old);
 295                 prev = cmpxchg(lock, old, new);
 296         } while (prev != old);
 297
 298         if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
 299                 DRM_ERROR("%d freed heavyweight lock held by %d\n",
 300                           context, _DRM_LOCKING_CONTEXT(old));
 301                 return 1;
 302         }
 303         wake_up_interruptible(&lock_data->lock_queue);
 304         return 0;
 305 }
 306
 307 /**
 308  * If we get here, it means that the process has called DRM_IOCTL_LOCK
 309  * without calling DRM_IOCTL_UNLOCK.
 310  *
 311  * If the lock is not held, then let the signal proceed as usual.  If the lock
 312  * is held, then set the contended flag and keep the signal blocked.
 313  *
 314  * \param priv pointer to a drm_sigdata structure.
 315  * \return one if the signal should be delivered normally, or zero if the
 316  * signal should be blocked.
 317  */
 318 static int drm_notifier(void *priv)
 319 {
 320         struct drm_sigdata *s = (struct drm_sigdata *) priv;
 321         unsigned int old, new, prev;
 322
 323         /* Allow signal delivery if lock isn't held */
 324         if (!s->lock || !_DRM_LOCK_IS_HELD(s->lock->lock)
 325             || _DRM_LOCKING_CONTEXT(s->lock->lock) != s->context)
 326                 return 1;
 327
 328         /* Otherwise, set flag to force call to
 329            drmUnlock */
 330         do {
 331                 old = s->lock->lock;
 332                 new = old | _DRM_LOCK_CONT;
 333                 prev = cmpxchg(&s->lock->lock, old, new);
 334         } while (prev != old);
 335         return 0;
 336 }
 337
 338 /**
 339  * This function returns immediately and takes the hw lock
 340  * with the kernel context if it is free, otherwise it gets the highest priority when and if
 341  * it is eventually released.
 342  *
 343  * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held
 344  * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause
 345  * a deadlock, which is why the "idlelock" was invented).
 346  *
 347  * This should be sufficient to wait for GPU idle without
 348  * having to worry about starvation.
 349  */
 350
 351 void drm_idlelock_take(struct drm_lock_data *lock_data)
 352 {
 353         int ret = 0;
 354
 355         spin_lock(&lock_data->spinlock);
 356         lock_data->kernel_waiters++;
 357         if (!lock_data->idle_has_lock) {
 358
 359                 spin_unlock(&lock_data->spinlock);
 360                 ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
 361                 spin_lock(&lock_data->spinlock);
 362
 363                 if (ret == 1)
 364                         lock_data->idle_has_lock = 1;
 365         }
 366         spin_unlock(&lock_data->spinlock);
 367 }
 368 EXPORT_SYMBOL(drm_idlelock_take);
 369
 370 void drm_idlelock_release(struct drm_lock_data *lock_data)
 371 {
 372         unsigned int old, prev;
 373         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 374
 375         spin_lock(&lock_data->spinlock);
 376         if (--lock_data->kernel_waiters == 0) {
 377                 if (lock_data->idle_has_lock) {
 378                         do {
 379                                 old = *lock;
 380                                 prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT);
 381                         } while (prev != old);
 382                         wake_up_interruptible(&lock_data->lock_queue);
 383                         lock_data->idle_has_lock = 0;
 384                 }
 385         }
 386         spin_unlock(&lock_data->spinlock);
 387 }
 388 EXPORT_SYMBOL(drm_idlelock_release);
 389
 390
 391 int drm_i_have_hw_lock(struct drm_file *file_priv)
 392 {
 393         DRM_DEVICE;
 394
 395         return (file_priv->lock_count && dev->lock.hw_lock &&
 396                 _DRM_LOCK_IS_HELD(dev->lock.hw_lock->lock) &&
 397                 dev->lock.file_priv == file_priv);
 398 }
 399
 400 EXPORT_SYMBOL(drm_i_have_hw_lock);