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         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                           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                   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                         send_sig(SIGTERM, current, 0);
  84                         ret = -EINTR;
  85                         break;
  86                 }
  87                 if (drm_lock_take(&master->lock, lock->context)) {
  88                         master->lock.file_priv = file_priv;
  89                         master->lock.lock_time = jiffies;
  90                         atomic_inc(&dev->counts[_DRM_STAT_LOCKS]);
  91                         break;  /* Got lock */
  92                 }
  93
  94                 /* Contention */
  95                 schedule();
  96                 if (signal_pending(current)) {
  97                         ret = -EINTR;
  98                         break;
  99                 }
 100         }
 101         spin_lock_bh(&master->lock.spinlock);
 102         master->lock.user_waiters--;
 103         spin_unlock_bh(&master->lock.spinlock);
 104         __set_current_state(TASK_RUNNING);
 105         remove_wait_queue(&master->lock.lock_queue, &entry);
 106
 107         DRM_DEBUG("%d %s\n", lock->context,
 108                   ret ? "interrupted" : "has lock");
 109         if (ret) return ret;
 110
 111         /* don't set the block all signals on the master process for now
 112          * really probably not the correct answer but lets us debug xkb
 113          * xserver for now */
 114         if (!file_priv->is_master) {
 115                 sigemptyset(&dev->sigmask);
 116                 sigaddset(&dev->sigmask, SIGSTOP);
 117                 sigaddset(&dev->sigmask, SIGTSTP);
 118                 sigaddset(&dev->sigmask, SIGTTIN);
 119                 sigaddset(&dev->sigmask, SIGTTOU);
 120                 dev->sigdata.context = lock->context;
 121                 dev->sigdata.lock = master->lock.hw_lock;
 122                 block_all_signals(drm_notifier, &dev->sigdata, &dev->sigmask);
 123         }
 124
 125         if (dev->driver->dma_ready && (lock->flags & _DRM_LOCK_READY))
 126                 dev->driver->dma_ready(dev);
 127
 128         if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT))
 129         {
 130                 if (dev->driver->dma_quiescent(dev)) {
 131                         DRM_DEBUG("%d waiting for DMA quiescent\n",
 132                                   lock->context);
 133                         return -EBUSY;
 134                 }
 135         }
 136
 137         if (dev->driver->kernel_context_switch &&
 138             dev->last_context != lock->context) {
 139                 dev->driver->kernel_context_switch(dev, dev->last_context,
 140                                                    lock->context);
 141         }
 142
 143         return 0;
 144 }
 145
 146 /**
 147  * Unlock ioctl.
 148  *
 149  * \param inode device inode.
 150  * \param file_priv DRM file private.
 151  * \param cmd command.
 152  * \param arg user argument, pointing to a drm_lock structure.
 153  * \return zero on success or negative number on failure.
 154  *
 155  * Transfer and free the lock.
 156  */
 157 int drm_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv)
 158 {
 159         struct drm_lock *lock = data;
 160         struct drm_master *master = file_priv->master;
 161
 162         if (lock->context == DRM_KERNEL_CONTEXT) {
 163                 DRM_ERROR("Process %d using kernel context %d\n",
 164                           task_pid_nr(current), lock->context);
 165                 return -EINVAL;
 166         }
 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(&master->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 EXPORT_SYMBOL(drm_lock_take);
 231
 232 /**
 233  * This takes a lock forcibly and hands it to context.  Should ONLY be used
 234  * inside *_unlock to give lock to kernel before calling *_dma_schedule.
 235  *
 236  * \param dev DRM device.
 237  * \param lock lock pointer.
 238  * \param context locking context.
 239  * \return always one.
 240  *
 241  * Resets the lock file pointer.
 242  * Marks the lock as held by the given context, via the \p cmpxchg instruction.
 243  */
 244 static int drm_lock_transfer(struct drm_lock_data *lock_data,
 245                              unsigned int context)
 246 {
 247         unsigned int old, new, prev;
 248         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 249
 250         lock_data->file_priv = NULL;
 251         do {
 252                 old = *lock;
 253                 new = context | _DRM_LOCK_HELD;
 254                 prev = cmpxchg(lock, old, new);
 255         } while (prev != old);
 256         return 1;
 257 }
 258
 259 /**
 260  * Free lock.
 261  *
 262  * \param dev DRM device.
 263  * \param lock lock.
 264  * \param context context.
 265  *
 266  * Resets the lock file pointer.
 267  * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
 268  * waiting on the lock queue.
 269  */
 270 int drm_lock_free(struct drm_lock_data *lock_data, unsigned int context)
 271 {
 272         unsigned int old, new, prev;
 273         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 274
 275         spin_lock_bh(&lock_data->spinlock);
 276         if (lock_data->kernel_waiters != 0) {
 277                 drm_lock_transfer(lock_data, 0);
 278                 lock_data->idle_has_lock = 1;
 279                 spin_unlock_bh(&lock_data->spinlock);
 280                 return 1;
 281         }
 282         spin_unlock_bh(&lock_data->spinlock);
 283
 284         do {
 285                 old = *lock;
 286                 new = _DRM_LOCKING_CONTEXT(old);
 287                 prev = cmpxchg(lock, old, new);
 288         } while (prev != old);
 289
 290         if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
 291                 DRM_ERROR("%d freed heavyweight lock held by %d\n",
 292                           context, _DRM_LOCKING_CONTEXT(old));
 293                 return 1;
 294         }
 295         wake_up_interruptible(&lock_data->lock_queue);
 296         return 0;
 297 }
 298 EXPORT_SYMBOL(drm_lock_free);
 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_bh(&lock_data->spinlock);
 349         lock_data->kernel_waiters++;
 350         if (!lock_data->idle_has_lock) {
 351
 352                 spin_unlock_bh(&lock_data->spinlock);
 353                 ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
 354                 spin_lock_bh(&lock_data->spinlock);
 355
 356                 if (ret == 1)
 357                         lock_data->idle_has_lock = 1;
 358         }
 359         spin_unlock_bh(&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_bh(&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_bh(&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         struct drm_master *master = file_priv->master;
 387         return (file_priv->lock_count && master->lock.hw_lock &&
 388                 _DRM_LOCK_IS_HELD(master->lock.hw_lock->lock) &&
 389                 master->lock.file_priv == file_priv);
 390 }
 391
 392 EXPORT_SYMBOL(drm_i_have_hw_lock);