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                 mutex_unlock(&drm_global_mutex);
  96                 schedule();
  97                 mutex_lock(&drm_global_mutex);
  98                 if (signal_pending(current)) {
  99                         ret = -EINTR;
 100                         break;
 101                 }
 102         }
 103         spin_lock_bh(&master->lock.spinlock);
 104         master->lock.user_waiters--;
 105         spin_unlock_bh(&master->lock.spinlock);
 106         __set_current_state(TASK_RUNNING);
 107         remove_wait_queue(&master->lock.lock_queue, &entry);
 108
 109         DRM_DEBUG("%d %s\n", lock->context,
 110                   ret ? "interrupted" : "has lock");
 111         if (ret) return ret;
 112
 113         /* don't set the block all signals on the master process for now
 114          * really probably not the correct answer but lets us debug xkb
 115          * xserver for now */
 116         if (!file_priv->is_master) {
 117                 sigemptyset(&dev->sigmask);
 118                 sigaddset(&dev->sigmask, SIGSTOP);
 119                 sigaddset(&dev->sigmask, SIGTSTP);
 120                 sigaddset(&dev->sigmask, SIGTTIN);
 121                 sigaddset(&dev->sigmask, SIGTTOU);
 122                 dev->sigdata.context = lock->context;
 123                 dev->sigdata.lock = master->lock.hw_lock;
 124                 block_all_signals(drm_notifier, &dev->sigdata, &dev->sigmask);
 125         }
 126
 127         if (dev->driver->dma_ready && (lock->flags & _DRM_LOCK_READY))
 128                 dev->driver->dma_ready(dev);
 129
 130         if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT))
 131         {
 132                 if (dev->driver->dma_quiescent(dev)) {
 133                         DRM_DEBUG("%d waiting for DMA quiescent\n",
 134                                   lock->context);
 135                         return -EBUSY;
 136                 }
 137         }
 138
 139         if (dev->driver->kernel_context_switch &&
 140             dev->last_context != lock->context) {
 141                 dev->driver->kernel_context_switch(dev, dev->last_context,
 142                                                    lock->context);
 143         }
 144
 145         return 0;
 146 }
 147
 148 /**
 149  * Unlock ioctl.
 150  *
 151  * \param inode device inode.
 152  * \param file_priv DRM file private.
 153  * \param cmd command.
 154  * \param arg user argument, pointing to a drm_lock structure.
 155  * \return zero on success or negative number on failure.
 156  *
 157  * Transfer and free the lock.
 158  */
 159 int drm_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv)
 160 {
 161         struct drm_lock *lock = data;
 162         struct drm_master *master = file_priv->master;
 163
 164         if (lock->context == DRM_KERNEL_CONTEXT) {
 165                 DRM_ERROR("Process %d using kernel context %d\n",
 166                           task_pid_nr(current), lock->context);
 167                 return -EINVAL;
 168         }
 169
 170         atomic_inc(&dev->counts[_DRM_STAT_UNLOCKS]);
 171
 172         /* kernel_context_switch isn't used by any of the x86 drm
 173          * modules but is required by the Sparc driver.
 174          */
 175         if (dev->driver->kernel_context_switch_unlock)
 176                 dev->driver->kernel_context_switch_unlock(dev);
 177         else {
 178                 if (drm_lock_free(&master->lock, lock->context)) {
 179                         /* FIXME: Should really bail out here. */
 180                 }
 181         }
 182
 183         unblock_all_signals();
 184         return 0;
 185 }
 186
 187 /**
 188  * Take the heavyweight lock.
 189  *
 190  * \param lock lock pointer.
 191  * \param context locking context.
 192  * \return one if the lock is held, or zero otherwise.
 193  *
 194  * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
 195  */
 196 int drm_lock_take(struct drm_lock_data *lock_data,
 197                   unsigned int context)
 198 {
 199         unsigned int old, new, prev;
 200         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 201
 202         spin_lock_bh(&lock_data->spinlock);
 203         do {
 204                 old = *lock;
 205                 if (old & _DRM_LOCK_HELD)
 206                         new = old | _DRM_LOCK_CONT;
 207                 else {
 208                         new = context | _DRM_LOCK_HELD |
 209                                 ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
 210                                  _DRM_LOCK_CONT : 0);
 211                 }
 212                 prev = cmpxchg(lock, old, new);
 213         } while (prev != old);
 214         spin_unlock_bh(&lock_data->spinlock);
 215
 216         if (_DRM_LOCKING_CONTEXT(old) == context) {
 217                 if (old & _DRM_LOCK_HELD) {
 218                         if (context != DRM_KERNEL_CONTEXT) {
 219                                 DRM_ERROR("%d holds heavyweight lock\n",
 220                                           context);
 221                         }
 222                         return 0;
 223                 }
 224         }
 225
 226         if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) {
 227                 /* Have lock */
 228                 return 1;
 229         }
 230         return 0;
 231 }
 232 EXPORT_SYMBOL(drm_lock_take);
 233
 234 /**
 235  * This takes a lock forcibly and hands it to context.  Should ONLY be used
 236  * inside *_unlock to give lock to kernel before calling *_dma_schedule.
 237  *
 238  * \param dev DRM device.
 239  * \param lock lock pointer.
 240  * \param context locking context.
 241  * \return always one.
 242  *
 243  * Resets the lock file pointer.
 244  * Marks the lock as held by the given context, via the \p cmpxchg instruction.
 245  */
 246 static int drm_lock_transfer(struct drm_lock_data *lock_data,
 247                              unsigned int context)
 248 {
 249         unsigned int old, new, prev;
 250         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 251
 252         lock_data->file_priv = NULL;
 253         do {
 254                 old = *lock;
 255                 new = context | _DRM_LOCK_HELD;
 256                 prev = cmpxchg(lock, old, new);
 257         } while (prev != old);
 258         return 1;
 259 }
 260
 261 /**
 262  * Free lock.
 263  *
 264  * \param dev DRM device.
 265  * \param lock lock.
 266  * \param context context.
 267  *
 268  * Resets the lock file pointer.
 269  * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
 270  * waiting on the lock queue.
 271  */
 272 int drm_lock_free(struct drm_lock_data *lock_data, unsigned int context)
 273 {
 274         unsigned int old, new, prev;
 275         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 276
 277         spin_lock_bh(&lock_data->spinlock);
 278         if (lock_data->kernel_waiters != 0) {
 279                 drm_lock_transfer(lock_data, 0);
 280                 lock_data->idle_has_lock = 1;
 281                 spin_unlock_bh(&lock_data->spinlock);
 282                 return 1;
 283         }
 284         spin_unlock_bh(&lock_data->spinlock);
 285
 286         do {
 287                 old = *lock;
 288                 new = _DRM_LOCKING_CONTEXT(old);
 289                 prev = cmpxchg(lock, old, new);
 290         } while (prev != old);
 291
 292         if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
 293                 DRM_ERROR("%d freed heavyweight lock held by %d\n",
 294                           context, _DRM_LOCKING_CONTEXT(old));
 295                 return 1;
 296         }
 297         wake_up_interruptible(&lock_data->lock_queue);
 298         return 0;
 299 }
 300 EXPORT_SYMBOL(drm_lock_free);
 301
 302 /**
 303  * If we get here, it means that the process has called DRM_IOCTL_LOCK
 304  * without calling DRM_IOCTL_UNLOCK.
 305  *
 306  * If the lock is not held, then let the signal proceed as usual.  If the lock
 307  * is held, then set the contended flag and keep the signal blocked.
 308  *
 309  * \param priv pointer to a drm_sigdata structure.
 310  * \return one if the signal should be delivered normally, or zero if the
 311  * signal should be blocked.
 312  */
 313 static int drm_notifier(void *priv)
 314 {
 315         struct drm_sigdata *s = (struct drm_sigdata *) priv;
 316         unsigned int old, new, prev;
 317
 318         /* Allow signal delivery if lock isn't held */
 319         if (!s->lock || !_DRM_LOCK_IS_HELD(s->lock->lock)
 320             || _DRM_LOCKING_CONTEXT(s->lock->lock) != s->context)
 321                 return 1;
 322
 323         /* Otherwise, set flag to force call to
 324            drmUnlock */
 325         do {
 326                 old = s->lock->lock;
 327                 new = old | _DRM_LOCK_CONT;
 328                 prev = cmpxchg(&s->lock->lock, old, new);
 329         } while (prev != old);
 330         return 0;
 331 }
 332
 333 /**
 334  * This function returns immediately and takes the hw lock
 335  * with the kernel context if it is free, otherwise it gets the highest priority when and if
 336  * it is eventually released.
 337  *
 338  * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held
 339  * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause
 340  * a deadlock, which is why the "idlelock" was invented).
 341  *
 342  * This should be sufficient to wait for GPU idle without
 343  * having to worry about starvation.
 344  */
 345
 346 void drm_idlelock_take(struct drm_lock_data *lock_data)
 347 {
 348         int ret = 0;
 349
 350         spin_lock_bh(&lock_data->spinlock);
 351         lock_data->kernel_waiters++;
 352         if (!lock_data->idle_has_lock) {
 353
 354                 spin_unlock_bh(&lock_data->spinlock);
 355                 ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
 356                 spin_lock_bh(&lock_data->spinlock);
 357
 358                 if (ret == 1)
 359                         lock_data->idle_has_lock = 1;
 360         }
 361         spin_unlock_bh(&lock_data->spinlock);
 362 }
 363 EXPORT_SYMBOL(drm_idlelock_take);
 364
 365 void drm_idlelock_release(struct drm_lock_data *lock_data)
 366 {
 367         unsigned int old, prev;
 368         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 369
 370         spin_lock_bh(&lock_data->spinlock);
 371         if (--lock_data->kernel_waiters == 0) {
 372                 if (lock_data->idle_has_lock) {
 373                         do {
 374                                 old = *lock;
 375                                 prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT);
 376                         } while (prev != old);
 377                         wake_up_interruptible(&lock_data->lock_queue);
 378                         lock_data->idle_has_lock = 0;
 379                 }
 380         }
 381         spin_unlock_bh(&lock_data->spinlock);
 382 }
 383 EXPORT_SYMBOL(drm_idlelock_release);
 384
 385
 386 int drm_i_have_hw_lock(struct drm_device *dev, struct drm_file *file_priv)
 387 {
 388         struct drm_master *master = file_priv->master;
 389         return (file_priv->lock_count && master->lock.hw_lock &&
 390                 _DRM_LOCK_IS_HELD(master->lock.hw_lock->lock) &&
 391                 master->lock.file_priv == file_priv);
 392 }
 393
 394 EXPORT_SYMBOL(drm_i_have_hw_lock);