drivers/gpu/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_bh(&dev->lock.spinlock);
  75         dev->lock.user_waiters++;
  76         spin_unlock_bh(&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_bh(&dev->lock.spinlock);
  99         dev->lock.user_waiters--;
 100         spin_unlock_bh(&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         void (*tasklet_func)(struct drm_device *);
 154
 155         if (lock->context == DRM_KERNEL_CONTEXT) {
 156                 DRM_ERROR("Process %d using kernel context %d\n",
 157                           task_pid_nr(current), lock->context);
 158                 return -EINVAL;
 159         }
 160
 161         spin_lock_irqsave(&dev->tasklet_lock, irqflags);
 162         tasklet_func = dev->locked_tasklet_func;
 163         dev->locked_tasklet_func = NULL;
 164         spin_unlock_irqrestore(&dev->tasklet_lock, irqflags);
 165         if (tasklet_func != NULL)
 166                 tasklet_func(dev);
 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);
 175         else {
 176                 if (drm_lock_free(&dev->lock,lock->context)) {
 177                         /* FIXME: Should really bail out here. */
 178                 }
 179         }
 180
 181         unblock_all_signals();
 182         return 0;
 183 }
 184
 185 /**
 186  * Take the heavyweight lock.
 187  *
 188  * \param lock lock pointer.
 189  * \param context locking context.
 190  * \return one if the lock is held, or zero otherwise.
 191  *
 192  * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
 193  */
 194 int drm_lock_take(struct drm_lock_data *lock_data,
 195                   unsigned int context)
 196 {
 197         unsigned int old, new, prev;
 198         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 199
 200         spin_lock_bh(&lock_data->spinlock);
 201         do {
 202                 old = *lock;
 203                 if (old & _DRM_LOCK_HELD)
 204                         new = old | _DRM_LOCK_CONT;
 205                 else {
 206                         new = context | _DRM_LOCK_HELD |
 207                                 ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
 208                                  _DRM_LOCK_CONT : 0);
 209                 }
 210                 prev = cmpxchg(lock, old, new);
 211         } while (prev != old);
 212         spin_unlock_bh(&lock_data->spinlock);
 213
 214         if (_DRM_LOCKING_CONTEXT(old) == context) {
 215                 if (old & _DRM_LOCK_HELD) {
 216                         if (context != DRM_KERNEL_CONTEXT) {
 217                                 DRM_ERROR("%d holds heavyweight lock\n",
 218                                           context);
 219                         }
 220                         return 0;
 221                 }
 222         }
 223
 224         if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) {
 225                 /* Have lock */
 226                 return 1;
 227         }
 228         return 0;
 229 }
 230
 231 /**
 232  * This takes a lock forcibly and hands it to context.  Should ONLY be used
 233  * inside *_unlock to give lock to kernel before calling *_dma_schedule.
 234  *
 235  * \param dev DRM device.
 236  * \param lock lock pointer.
 237  * \param context locking context.
 238  * \return always one.
 239  *
 240  * Resets the lock file pointer.
 241  * Marks the lock as held by the given context, via the \p cmpxchg instruction.
 242  */
 243 static int drm_lock_transfer(struct drm_lock_data *lock_data,
 244                              unsigned int context)
 245 {
 246         unsigned int old, new, prev;
 247         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 248
 249         lock_data->file_priv = NULL;
 250         do {
 251                 old = *lock;
 252                 new = context | _DRM_LOCK_HELD;
 253                 prev = cmpxchg(lock, old, new);
 254         } while (prev != old);
 255         return 1;
 256 }
 257
 258 /**
 259  * Free lock.
 260  *
 261  * \param dev DRM device.
 262  * \param lock lock.
 263  * \param context context.
 264  *
 265  * Resets the lock file pointer.
 266  * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
 267  * waiting on the lock queue.
 268  */
 269 int drm_lock_free(struct drm_lock_data *lock_data, unsigned int context)
 270 {
 271         unsigned int old, new, prev;
 272         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 273
 274         spin_lock_bh(&lock_data->spinlock);
 275         if (lock_data->kernel_waiters != 0) {
 276                 drm_lock_transfer(lock_data, 0);
 277                 lock_data->idle_has_lock = 1;
 278                 spin_unlock_bh(&lock_data->spinlock);
 279                 return 1;
 280         }
 281         spin_unlock_bh(&lock_data->spinlock);
 282
 283         do {
 284                 old = *lock;
 285                 new = _DRM_LOCKING_CONTEXT(old);
 286                 prev = cmpxchg(lock, old, new);
 287         } while (prev != old);
 288
 289         if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
 290                 DRM_ERROR("%d freed heavyweight lock held by %d\n",
 291                           context, _DRM_LOCKING_CONTEXT(old));
 292                 return 1;
 293         }
 294         wake_up_interruptible(&lock_data->lock_queue);
 295         return 0;
 296 }
 297
 298 /**
 299  * If we get here, it means that the process has called DRM_IOCTL_LOCK
 300  * without calling DRM_IOCTL_UNLOCK.
 301  *
 302  * If the lock is not held, then let the signal proceed as usual.  If the lock
 303  * is held, then set the contended flag and keep the signal blocked.
 304  *
 305  * \param priv pointer to a drm_sigdata structure.
 306  * \return one if the signal should be delivered normally, or zero if the
 307  * signal should be blocked.
 308  */
 309 static int drm_notifier(void *priv)
 310 {
 311         struct drm_sigdata *s = (struct drm_sigdata *) priv;
 312         unsigned int old, new, prev;
 313
 314         /* Allow signal delivery if lock isn't held */
 315         if (!s->lock || !_DRM_LOCK_IS_HELD(s->lock->lock)
 316             || _DRM_LOCKING_CONTEXT(s->lock->lock) != s->context)
 317                 return 1;
 318
 319         /* Otherwise, set flag to force call to
 320            drmUnlock */
 321         do {
 322                 old = s->lock->lock;
 323                 new = old | _DRM_LOCK_CONT;
 324                 prev = cmpxchg(&s->lock->lock, old, new);
 325         } while (prev != old);
 326         return 0;
 327 }
 328
 329 /**
 330  * This function returns immediately and takes the hw lock
 331  * with the kernel context if it is free, otherwise it gets the highest priority when and if
 332  * it is eventually released.
 333  *
 334  * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held
 335  * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause
 336  * a deadlock, which is why the "idlelock" was invented).
 337  *
 338  * This should be sufficient to wait for GPU idle without
 339  * having to worry about starvation.
 340  */
 341
 342 void drm_idlelock_take(struct drm_lock_data *lock_data)
 343 {
 344         int ret = 0;
 345
 346         spin_lock_bh(&lock_data->spinlock);
 347         lock_data->kernel_waiters++;
 348         if (!lock_data->idle_has_lock) {
 349
 350                 spin_unlock_bh(&lock_data->spinlock);
 351                 ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
 352                 spin_lock_bh(&lock_data->spinlock);
 353
 354                 if (ret == 1)
 355                         lock_data->idle_has_lock = 1;
 356         }
 357         spin_unlock_bh(&lock_data->spinlock);
 358 }
 359 EXPORT_SYMBOL(drm_idlelock_take);
 360
 361 void drm_idlelock_release(struct drm_lock_data *lock_data)
 362 {
 363         unsigned int old, prev;
 364         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 365
 366         spin_lock_bh(&lock_data->spinlock);
 367         if (--lock_data->kernel_waiters == 0) {
 368                 if (lock_data->idle_has_lock) {
 369                         do {
 370                                 old = *lock;
 371                                 prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT);
 372                         } while (prev != old);
 373                         wake_up_interruptible(&lock_data->lock_queue);
 374                         lock_data->idle_has_lock = 0;
 375                 }
 376         }
 377         spin_unlock_bh(&lock_data->spinlock);
 378 }
 379 EXPORT_SYMBOL(drm_idlelock_release);
 380
 381
 382 int drm_i_have_hw_lock(struct drm_device *dev, struct drm_file *file_priv)
 383 {
 384         return (file_priv->lock_count && dev->lock.hw_lock &&
 385                 _DRM_LOCK_IS_HELD(dev->lock.hw_lock->lock) &&
 386                 dev->lock.file_priv == file_priv);
 387 }
 388
 389 EXPORT_SYMBOL(drm_i_have_hw_lock);