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