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         int ret = 0;
  56
  57         ++file_priv->lock_count;
  58
  59         if (lock->context == DRM_KERNEL_CONTEXT) {
  60                 DRM_ERROR("Process %d using kernel context %d\n",
  61                           task_pid_nr(current), lock->context);
  62                 return -EINVAL;
  63         }
  64
  65         DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
  66                   lock->context, task_pid_nr(current),
  67                   dev->lock.hw_lock->lock, lock->flags);
  68
  69         if (drm_core_check_feature(dev, DRIVER_DMA_QUEUE))
  70                 if (lock->context < 0)
  71                         return -EINVAL;
  72
  73         add_wait_queue(&dev->lock.lock_queue, &entry);
  74         spin_lock_bh(&dev->lock.spinlock);
  75         dev->lock.user_waiters++;
  76         spin_unlock_bh(&dev->lock.spinlock);
  77         for (;;) {
  78                 __set_current_state(TASK_INTERRUPTIBLE);
  79                 if (!dev->lock.hw_lock) {
  80                         /* Device has been unregistered */
  81                         ret = -EINTR;
  82                         break;
  83                 }
  84                 if (drm_lock_take(&dev->lock, lock->context)) {
  85                         dev->lock.file_priv = file_priv;
  86                         dev->lock.lock_time = jiffies;
  87                         atomic_inc(&dev->counts[_DRM_STAT_LOCKS]);
  88                         break;  /* Got lock */
  89                 }
  90
  91                 /* Contention */
  92                 schedule();
  93                 if (signal_pending(current)) {
  94                         ret = -ERESTARTSYS;
  95                         break;
  96                 }
  97         }
  98         spin_lock_bh(&dev->lock.spinlock);
  99         dev->lock.user_waiters--;
 100         spin_unlock_bh(&dev->lock.spinlock);
 101         __set_current_state(TASK_RUNNING);
 102         remove_wait_queue(&dev->lock.lock_queue, &entry);
 103
 104         DRM_DEBUG("%d %s\n", lock->context,
 105                   ret ? "interrupted" : "has lock");
 106         if (ret) return ret;
 107
 108         /* don't set the block all signals on the master process for now
 109          * really probably not the correct answer but lets us debug xkb
 110          * xserver for now */
 111         if (!file_priv->master) {
 112                 sigemptyset(&dev->sigmask);
 113                 sigaddset(&dev->sigmask, SIGSTOP);
 114                 sigaddset(&dev->sigmask, SIGTSTP);
 115                 sigaddset(&dev->sigmask, SIGTTIN);
 116                 sigaddset(&dev->sigmask, SIGTTOU);
 117                 dev->sigdata.context = lock->context;
 118                 dev->sigdata.lock = dev->lock.hw_lock;
 119                 block_all_signals(drm_notifier, &dev->sigdata, &dev->sigmask);
 120         }
 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         {
 127                 if (dev->driver->dma_quiescent(dev)) {
 128                         DRM_DEBUG("%d waiting for DMA quiescent\n",
 129                                   lock->context);
 130                         return -EBUSY;
 131                 }
 132         }
 133
 134         if (dev->driver->kernel_context_switch &&
 135             dev->last_context != lock->context) {
 136                 dev->driver->kernel_context_switch(dev, dev->last_context,
 137                                                    lock->context);
 138         }
 139
 140         return 0;
 141 }
 142
 143 /**
 144  * Unlock ioctl.
 145  *
 146  * \param inode device inode.
 147  * \param file_priv DRM file private.
 148  * \param cmd command.
 149  * \param arg user argument, pointing to a drm_lock structure.
 150  * \return zero on success or negative number on failure.
 151  *
 152  * Transfer and free the lock.
 153  */
 154 int drm_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv)
 155 {
 156         struct drm_lock *lock = data;
 157         unsigned long irqflags;
 158         void (*tasklet_func)(struct drm_device *);
 159
 160         if (lock->context == DRM_KERNEL_CONTEXT) {
 161                 DRM_ERROR("Process %d using kernel context %d\n",
 162                           task_pid_nr(current), lock->context);
 163                 return -EINVAL;
 164         }
 165
 166         spin_lock_irqsave(&dev->tasklet_lock, irqflags);
 167         tasklet_func = dev->locked_tasklet_func;
 168         dev->locked_tasklet_func = NULL;
 169         spin_unlock_irqrestore(&dev->tasklet_lock, irqflags);
 170         if (tasklet_func != NULL)
 171                 tasklet_func(dev);
 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(&dev->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                 return 1;
 232         }
 233         return 0;
 234 }
 235
 236 /**
 237  * This takes a lock forcibly and hands it to context.  Should ONLY be used
 238  * inside *_unlock to give lock to kernel before calling *_dma_schedule.
 239  *
 240  * \param dev DRM device.
 241  * \param lock lock pointer.
 242  * \param context locking context.
 243  * \return always one.
 244  *
 245  * Resets the lock file pointer.
 246  * Marks the lock as held by the given context, via the \p cmpxchg instruction.
 247  */
 248 static int drm_lock_transfer(struct drm_lock_data *lock_data,
 249                              unsigned int context)
 250 {
 251         unsigned int old, new, prev;
 252         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 253
 254         lock_data->file_priv = NULL;
 255         do {
 256                 old = *lock;
 257                 new = context | _DRM_LOCK_HELD;
 258                 prev = cmpxchg(lock, old, new);
 259         } while (prev != old);
 260         return 1;
 261 }
 262
 263 /**
 264  * Free lock.
 265  *
 266  * \param dev DRM device.
 267  * \param lock lock.
 268  * \param context context.
 269  *
 270  * Resets the lock file pointer.
 271  * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
 272  * waiting on the lock queue.
 273  */
 274 int drm_lock_free(struct drm_lock_data *lock_data, unsigned int context)
 275 {
 276         unsigned int old, new, prev;
 277         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 278
 279         spin_lock_bh(&lock_data->spinlock);
 280         if (lock_data->kernel_waiters != 0) {
 281                 drm_lock_transfer(lock_data, 0);
 282                 lock_data->idle_has_lock = 1;
 283                 spin_unlock_bh(&lock_data->spinlock);
 284                 return 1;
 285         }
 286         spin_unlock_bh(&lock_data->spinlock);
 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
 351         spin_lock_bh(&lock_data->spinlock);
 352         lock_data->kernel_waiters++;
 353         if (!lock_data->idle_has_lock) {
 354
 355                 spin_unlock_bh(&lock_data->spinlock);
 356                 ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
 357                 spin_lock_bh(&lock_data->spinlock);
 358
 359                 if (ret == 1)
 360                         lock_data->idle_has_lock = 1;
 361         }
 362         spin_unlock_bh(&lock_data->spinlock);
 363 }
 364 EXPORT_SYMBOL(drm_idlelock_take);
 365
 366 void drm_idlelock_release(struct drm_lock_data *lock_data)
 367 {
 368         unsigned int old, prev;
 369         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 370
 371         spin_lock_bh(&lock_data->spinlock);
 372         if (--lock_data->kernel_waiters == 0) {
 373                 if (lock_data->idle_has_lock) {
 374                         do {
 375                                 old = *lock;
 376                                 prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT);
 377                         } while (prev != old);
 378                         wake_up_interruptible(&lock_data->lock_queue);
 379                         lock_data->idle_has_lock = 0;
 380                 }
 381         }
 382         spin_unlock_bh(&lock_data->spinlock);
 383 }
 384 EXPORT_SYMBOL(drm_idlelock_release);
 385
 386
 387 int drm_i_have_hw_lock(struct drm_device *dev, struct drm_file *file_priv)
 388 {
 389         return (file_priv->lock_count && dev->lock.hw_lock &&
 390                 _DRM_LOCK_IS_HELD(dev->lock.hw_lock->lock) &&
 391                 dev->lock.file_priv == file_priv);
 392 }
 393
 394 EXPORT_SYMBOL(drm_i_have_hw_lock);