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