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