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                         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         /* don't set the block all signals on the master process for now
 111          * really probably not the correct answer but lets us debug xkb
 112          * xserver for now */
 113         if (!file_priv->is_master) {
 114                 sigemptyset(&dev->sigmask);
 115                 sigaddset(&dev->sigmask, SIGSTOP);
 116                 sigaddset(&dev->sigmask, SIGTSTP);
 117                 sigaddset(&dev->sigmask, SIGTTIN);
 118                 sigaddset(&dev->sigmask, SIGTTOU);
 119                 dev->sigdata.context = lock->context;
 120                 dev->sigdata.lock = master->lock.hw_lock;
 121                 block_all_signals(drm_notifier, &dev->sigdata, &dev->sigmask);
 122         }
 123
 124         if (dev->driver->dma_ready && (lock->flags & _DRM_LOCK_READY))
 125                 dev->driver->dma_ready(dev);
 126
 127         if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT))
 128         {
 129                 if (dev->driver->dma_quiescent(dev)) {
 130                         DRM_DEBUG("%d waiting for DMA quiescent\n",
 131                                   lock->context);
 132                         return -EBUSY;
 133                 }
 134         }
 135
 136         if (dev->driver->kernel_context_switch &&
 137             dev->last_context != lock->context) {
 138                 dev->driver->kernel_context_switch(dev, dev->last_context,
 139                                                    lock->context);
 140         }
 141
 142         return 0;
 143 }
 144
 145 /**
 146  * Unlock ioctl.
 147  *
 148  * \param inode device inode.
 149  * \param file_priv DRM file private.
 150  * \param cmd command.
 151  * \param arg user argument, pointing to a drm_lock structure.
 152  * \return zero on success or negative number on failure.
 153  *
 154  * Transfer and free the lock.
 155  */
 156 int drm_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv)
 157 {
 158         struct drm_lock *lock = data;
 159         struct drm_master *master = file_priv->master;
 160
 161         if (lock->context == DRM_KERNEL_CONTEXT) {
 162                 DRM_ERROR("Process %d using kernel context %d\n",
 163                           task_pid_nr(current), lock->context);
 164                 return -EINVAL;
 165         }
 166
 167         atomic_inc(&dev->counts[_DRM_STAT_UNLOCKS]);
 168
 169         /* kernel_context_switch isn't used by any of the x86 drm
 170          * modules but is required by the Sparc driver.
 171          */
 172         if (dev->driver->kernel_context_switch_unlock)
 173                 dev->driver->kernel_context_switch_unlock(dev);
 174         else {
 175                 if (drm_lock_free(&master->lock, lock->context)) {
 176                         /* FIXME: Should really bail out here. */
 177                 }
 178         }
 179
 180         unblock_all_signals();
 181         return 0;
 182 }
 183
 184 /**
 185  * Take the heavyweight lock.
 186  *
 187  * \param lock lock pointer.
 188  * \param context locking context.
 189  * \return one if the lock is held, or zero otherwise.
 190  *
 191  * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
 192  */
 193 int drm_lock_take(struct drm_lock_data *lock_data,
 194                   unsigned int context)
 195 {
 196         unsigned int old, new, prev;
 197         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 198
 199         spin_lock_bh(&lock_data->spinlock);
 200         do {
 201                 old = *lock;
 202                 if (old & _DRM_LOCK_HELD)
 203                         new = old | _DRM_LOCK_CONT;
 204                 else {
 205                         new = context | _DRM_LOCK_HELD |
 206                                 ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
 207                                  _DRM_LOCK_CONT : 0);
 208                 }
 209                 prev = cmpxchg(lock, old, new);
 210         } while (prev != old);
 211         spin_unlock_bh(&lock_data->spinlock);
 212
 213         if (_DRM_LOCKING_CONTEXT(old) == context) {
 214                 if (old & _DRM_LOCK_HELD) {
 215                         if (context != DRM_KERNEL_CONTEXT) {
 216                                 DRM_ERROR("%d holds heavyweight lock\n",
 217                                           context);
 218                         }
 219                         return 0;
 220                 }
 221         }
 222
 223         if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) {
 224                 /* Have lock */
 225                 return 1;
 226         }
 227         return 0;
 228 }
 229 EXPORT_SYMBOL(drm_lock_take);
 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 EXPORT_SYMBOL(drm_lock_free);
 298
 299 /**
 300  * If we get here, it means that the process has called DRM_IOCTL_LOCK
 301  * without calling DRM_IOCTL_UNLOCK.
 302  *
 303  * If the lock is not held, then let the signal proceed as usual.  If the lock
 304  * is held, then set the contended flag and keep the signal blocked.
 305  *
 306  * \param priv pointer to a drm_sigdata structure.
 307  * \return one if the signal should be delivered normally, or zero if the
 308  * signal should be blocked.
 309  */
 310 static int drm_notifier(void *priv)
 311 {
 312         struct drm_sigdata *s = (struct drm_sigdata *) priv;
 313         unsigned int old, new, prev;
 314
 315         /* Allow signal delivery if lock isn't held */
 316         if (!s->lock || !_DRM_LOCK_IS_HELD(s->lock->lock)
 317             || _DRM_LOCKING_CONTEXT(s->lock->lock) != s->context)
 318                 return 1;
 319
 320         /* Otherwise, set flag to force call to
 321            drmUnlock */
 322         do {
 323                 old = s->lock->lock;
 324                 new = old | _DRM_LOCK_CONT;
 325                 prev = cmpxchg(&s->lock->lock, old, new);
 326         } while (prev != old);
 327         return 0;
 328 }
 329
 330 /**
 331  * This function returns immediately and takes the hw lock
 332  * with the kernel context if it is free, otherwise it gets the highest priority when and if
 333  * it is eventually released.
 334  *
 335  * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held
 336  * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause
 337  * a deadlock, which is why the "idlelock" was invented).
 338  *
 339  * This should be sufficient to wait for GPU idle without
 340  * having to worry about starvation.
 341  */
 342
 343 void drm_idlelock_take(struct drm_lock_data *lock_data)
 344 {
 345         int ret = 0;
 346
 347         spin_lock_bh(&lock_data->spinlock);
 348         lock_data->kernel_waiters++;
 349         if (!lock_data->idle_has_lock) {
 350
 351                 spin_unlock_bh(&lock_data->spinlock);
 352                 ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
 353                 spin_lock_bh(&lock_data->spinlock);
 354
 355                 if (ret == 1)
 356                         lock_data->idle_has_lock = 1;
 357         }
 358         spin_unlock_bh(&lock_data->spinlock);
 359 }
 360 EXPORT_SYMBOL(drm_idlelock_take);
 361
 362 void drm_idlelock_release(struct drm_lock_data *lock_data)
 363 {
 364         unsigned int old, prev;
 365         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 366
 367         spin_lock_bh(&lock_data->spinlock);
 368         if (--lock_data->kernel_waiters == 0) {
 369                 if (lock_data->idle_has_lock) {
 370                         do {
 371                                 old = *lock;
 372                                 prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT);
 373                         } while (prev != old);
 374                         wake_up_interruptible(&lock_data->lock_queue);
 375                         lock_data->idle_has_lock = 0;
 376                 }
 377         }
 378         spin_unlock_bh(&lock_data->spinlock);
 379 }
 380 EXPORT_SYMBOL(drm_idlelock_release);
 381
 382
 383 int drm_i_have_hw_lock(struct drm_device *dev, struct drm_file *file_priv)
 384 {
 385         struct drm_master *master = file_priv->master;
 386         return (file_priv->lock_count && master->lock.hw_lock &&
 387                 _DRM_LOCK_IS_HELD(master->lock.hw_lock->lock) &&
 388                 master->lock.file_priv == file_priv);
 389 }
 390
 391 EXPORT_SYMBOL(drm_i_have_hw_lock);