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 filp file pointer.
  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 file *filp,
  52              unsigned int cmd, unsigned long arg)
  53 {
  54         drm_file_t *priv = filp->private_data;
  55         drm_device_t *dev = priv->head->dev;
  56         DECLARE_WAITQUEUE(entry, current);
  57         drm_lock_t lock;
  58         int ret = 0;
  59
  60         ++priv->lock_count;
  61
  62         if (copy_from_user(&lock, (drm_lock_t __user *) arg, sizeof(lock)))
  63                 return -EFAULT;
  64
  65         if (lock.context == DRM_KERNEL_CONTEXT) {
  66                 DRM_ERROR("Process %d using kernel context %d\n",
  67                           current->pid, lock.context);
  68                 return -EINVAL;
  69         }
  70
  71         DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
  72                   lock.context, current->pid,
  73                   dev->lock.hw_lock->lock, lock.flags);
  74
  75         if (drm_core_check_feature(dev, DRIVER_DMA_QUEUE))
  76                 if (lock.context < 0)
  77                         return -EINVAL;
  78
  79         add_wait_queue(&dev->lock.lock_queue, &entry);
  80         spin_lock(&dev->lock.spinlock);
  81         dev->lock.user_waiters++;
  82         spin_unlock(&dev->lock.spinlock);
  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, 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         spin_lock(&dev->lock.spinlock);
 105         dev->lock.user_waiters--;
 106         spin_unlock(&dev->lock.spinlock);
 107         __set_current_state(TASK_RUNNING);
 108         remove_wait_queue(&dev->lock.lock_queue, &entry);
 109
 110         DRM_DEBUG( "%d %s\n", lock.context, ret ? "interrupted" : "has lock" );
 111         if (ret) return ret;
 112
 113         sigemptyset(&dev->sigmask);
 114         sigaddset(&dev->sigmask, SIGSTOP);
 115         sigaddset(&dev->sigmask, SIGTSTP);
 116         sigaddset(&dev->sigmask, SIGTTIN);
 117         sigaddset(&dev->sigmask, SIGTTOU);
 118         dev->sigdata.context = lock.context;
 119         dev->sigdata.lock = dev->lock.hw_lock;
 120         block_all_signals(drm_notifier, &dev->sigdata, &dev->sigmask);
 121
 122         if (dev->driver->dma_ready && (lock.flags & _DRM_LOCK_READY))
 123                 dev->driver->dma_ready(dev);
 124
 125         if (dev->driver->dma_quiescent && (lock.flags & _DRM_LOCK_QUIESCENT)) {
 126                 if (dev->driver->dma_quiescent(dev)) {
 127                         DRM_DEBUG("%d waiting for DMA quiescent\n", lock.context);
 128                         return DRM_ERR(EBUSY);
 129                 }
 130         }
 131
 132         if (dev->driver->kernel_context_switch &&
 133             dev->last_context != lock.context) {
 134                 dev->driver->kernel_context_switch(dev, dev->last_context,
 135                                                    lock.context);
 136         }
 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         unsigned long irqflags;
 159
 160         if (copy_from_user(&lock, (drm_lock_t __user *) arg, sizeof(lock)))
 161                 return -EFAULT;
 162
 163         if (lock.context == DRM_KERNEL_CONTEXT) {
 164                 DRM_ERROR("Process %d using kernel context %d\n",
 165                           current->pid, lock.context);
 166                 return -EINVAL;
 167         }
 168
 169         spin_lock_irqsave(&dev->tasklet_lock, irqflags);
 170
 171         if (dev->locked_tasklet_func) {
 172                 dev->locked_tasklet_func(dev);
 173
 174                 dev->locked_tasklet_func = NULL;
 175         }
 176
 177         spin_unlock_irqrestore(&dev->tasklet_lock, irqflags);
 178
 179         atomic_inc(&dev->counts[_DRM_STAT_UNLOCKS]);
 180
 181         /* kernel_context_switch isn't used by any of the x86 drm
 182          * modules but is required by the Sparc driver.
 183          */
 184         if (dev->driver->kernel_context_switch_unlock)
 185                 dev->driver->kernel_context_switch_unlock(dev);
 186         else {
 187                 if (drm_lock_free(&dev->lock,lock.context)) {
 188                         /* FIXME: Should really bail out here. */
 189                 }
 190         }
 191
 192         unblock_all_signals();
 193         return 0;
 194 }
 195
 196 /**
 197  * Take the heavyweight lock.
 198  *
 199  * \param lock lock pointer.
 200  * \param context locking context.
 201  * \return one if the lock is held, or zero otherwise.
 202  *
 203  * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
 204  */
 205 int drm_lock_take(drm_lock_data_t *lock_data,
 206                   unsigned int context)
 207 {
 208         unsigned int old, new, prev;
 209         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 210
 211         spin_lock(&lock_data->spinlock);
 212         do {
 213                 old = *lock;
 214                 if (old & _DRM_LOCK_HELD)
 215                         new = old | _DRM_LOCK_CONT;
 216                 else {
 217                         new = context | _DRM_LOCK_HELD |
 218                                 ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
 219                                  _DRM_LOCK_CONT : 0);
 220                 }
 221                 prev = cmpxchg(lock, old, new);
 222         } while (prev != old);
 223         spin_unlock(&lock_data->spinlock);
 224
 225         if (_DRM_LOCKING_CONTEXT(old) == context) {
 226                 if (old & _DRM_LOCK_HELD) {
 227                         if (context != DRM_KERNEL_CONTEXT) {
 228                                 DRM_ERROR("%d holds heavyweight lock\n",
 229                                           context);
 230                         }
 231                         return 0;
 232                 }
 233         }
 234
 235         if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) {
 236                 /* Have lock */
 237                 return 1;
 238         }
 239         return 0;
 240 }
 241
 242 /**
 243  * This takes a lock forcibly and hands it to context.  Should ONLY be used
 244  * inside *_unlock to give lock to kernel before calling *_dma_schedule.
 245  *
 246  * \param dev DRM device.
 247  * \param lock lock pointer.
 248  * \param context locking context.
 249  * \return always one.
 250  *
 251  * Resets the lock file pointer.
 252  * Marks the lock as held by the given context, via the \p cmpxchg instruction.
 253  */
 254 static int drm_lock_transfer(drm_lock_data_t *lock_data,
 255                              unsigned int context)
 256 {
 257         unsigned int old, new, prev;
 258         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 259
 260         lock_data->filp = NULL;
 261         do {
 262                 old = *lock;
 263                 new = context | _DRM_LOCK_HELD;
 264                 prev = cmpxchg(lock, old, new);
 265         } while (prev != old);
 266         return 1;
 267 }
 268
 269 /**
 270  * Free lock.
 271  *
 272  * \param dev DRM device.
 273  * \param lock lock.
 274  * \param context context.
 275  *
 276  * Resets the lock file pointer.
 277  * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
 278  * waiting on the lock queue.
 279  */
 280 int drm_lock_free(drm_lock_data_t *lock_data, unsigned int context)
 281 {
 282         unsigned int old, new, prev;
 283         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 284
 285         spin_lock(&lock_data->spinlock);
 286         if (lock_data->kernel_waiters != 0) {
 287                 drm_lock_transfer(lock_data, 0);
 288                 lock_data->idle_has_lock = 1;
 289                 spin_unlock(&lock_data->spinlock);
 290                 return 1;
 291         }
 292         spin_unlock(&lock_data->spinlock);
 293
 294         do {
 295                 old = *lock;
 296                 new = _DRM_LOCKING_CONTEXT(old);
 297                 prev = cmpxchg(lock, old, new);
 298         } while (prev != old);
 299
 300         if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
 301                 DRM_ERROR("%d freed heavyweight lock held by %d\n",
 302                           context, _DRM_LOCKING_CONTEXT(old));
 303                 return 1;
 304         }
 305         wake_up_interruptible(&lock_data->lock_queue);
 306         return 0;
 307 }
 308
 309 /**
 310  * If we get here, it means that the process has called DRM_IOCTL_LOCK
 311  * without calling DRM_IOCTL_UNLOCK.
 312  *
 313  * If the lock is not held, then let the signal proceed as usual.  If the lock
 314  * is held, then set the contended flag and keep the signal blocked.
 315  *
 316  * \param priv pointer to a drm_sigdata structure.
 317  * \return one if the signal should be delivered normally, or zero if the
 318  * signal should be blocked.
 319  */
 320 static int drm_notifier(void *priv)
 321 {
 322         drm_sigdata_t *s = (drm_sigdata_t *) priv;
 323         unsigned int old, new, prev;
 324
 325         /* Allow signal delivery if lock isn't held */
 326         if (!s->lock || !_DRM_LOCK_IS_HELD(s->lock->lock)
 327             || _DRM_LOCKING_CONTEXT(s->lock->lock) != s->context)
 328                 return 1;
 329
 330         /* Otherwise, set flag to force call to
 331            drmUnlock */
 332         do {
 333                 old = s->lock->lock;
 334                 new = old | _DRM_LOCK_CONT;
 335                 prev = cmpxchg(&s->lock->lock, old, new);
 336         } while (prev != old);
 337         return 0;
 338 }
 339
 340 /**
 341  * This function returns immediately and takes the hw lock
 342  * with the kernel context if it is free, otherwise it gets the highest priority when and if
 343  * it is eventually released.
 344  *
 345  * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held
 346  * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause
 347  * a deadlock, which is why the "idlelock" was invented).
 348  *
 349  * This should be sufficient to wait for GPU idle without
 350  * having to worry about starvation.
 351  */
 352
 353 void drm_idlelock_take(drm_lock_data_t *lock_data)
 354 {
 355         int ret = 0;
 356
 357         spin_lock(&lock_data->spinlock);
 358         lock_data->kernel_waiters++;
 359         if (!lock_data->idle_has_lock) {
 360
 361                 spin_unlock(&lock_data->spinlock);
 362                 ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
 363                 spin_lock(&lock_data->spinlock);
 364
 365                 if (ret == 1)
 366                         lock_data->idle_has_lock = 1;
 367         }
 368         spin_unlock(&lock_data->spinlock);
 369 }
 370 EXPORT_SYMBOL(drm_idlelock_take);
 371
 372 void drm_idlelock_release(drm_lock_data_t *lock_data)
 373 {
 374         unsigned int old, prev;
 375         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 376
 377         spin_lock(&lock_data->spinlock);
 378         if (--lock_data->kernel_waiters == 0) {
 379                 if (lock_data->idle_has_lock) {
 380                         do {
 381                                 old = *lock;
 382                                 prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT);
 383                         } while (prev != old);
 384                         wake_up_interruptible(&lock_data->lock_queue);
 385                         lock_data->idle_has_lock = 0;
 386                 }
 387         }
 388         spin_unlock(&lock_data->spinlock);
 389 }
 390 EXPORT_SYMBOL(drm_idlelock_release);
 391
 392
 393 int drm_i_have_hw_lock(struct file *filp)
 394 {
 395         DRM_DEVICE;
 396
 397         return (priv->lock_count && dev->lock.hw_lock &&
 398                 _DRM_LOCK_IS_HELD(dev->lock.hw_lock->lock) &&
 399                 dev->lock.filp == filp);
 400 }
 401
 402 EXPORT_SYMBOL(drm_i_have_hw_lock);