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   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
 158         if (lock->context == DRM_KERNEL_CONTEXT) {
 159                 DRM_ERROR("Process %d using kernel context %d\n",
 160                           task_pid_nr(current), lock->context);
 161                 return -EINVAL;
 162         }
 163
 164         atomic_inc(&dev->counts[_DRM_STAT_UNLOCKS]);
 165
 166         /* kernel_context_switch isn't used by any of the x86 drm
 167          * modules but is required by the Sparc driver.
 168          */
 169         if (dev->driver->kernel_context_switch_unlock)
 170                 dev->driver->kernel_context_switch_unlock(dev);
 171         else {
 172                 if (drm_lock_free(&dev->lock,lock->context)) {
 173                         /* FIXME: Should really bail out here. */
 174                 }
 175         }
 176
 177         unblock_all_signals();
 178         return 0;
 179 }
 180
 181 /**
 182  * Take the heavyweight lock.
 183  *
 184  * \param lock lock pointer.
 185  * \param context locking context.
 186  * \return one if the lock is held, or zero otherwise.
 187  *
 188  * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
 189  */
 190 int drm_lock_take(struct drm_lock_data *lock_data,
 191                   unsigned int context)
 192 {
 193         unsigned int old, new, prev;
 194         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 195
 196         spin_lock_bh(&lock_data->spinlock);
 197         do {
 198                 old = *lock;
 199                 if (old & _DRM_LOCK_HELD)
 200                         new = old | _DRM_LOCK_CONT;
 201                 else {
 202                         new = context | _DRM_LOCK_HELD |
 203                                 ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
 204                                  _DRM_LOCK_CONT : 0);
 205                 }
 206                 prev = cmpxchg(lock, old, new);
 207         } while (prev != old);
 208         spin_unlock_bh(&lock_data->spinlock);
 209
 210         if (_DRM_LOCKING_CONTEXT(old) == context) {
 211                 if (old & _DRM_LOCK_HELD) {
 212                         if (context != DRM_KERNEL_CONTEXT) {
 213                                 DRM_ERROR("%d holds heavyweight lock\n",
 214                                           context);
 215                         }
 216                         return 0;
 217                 }
 218         }
 219
 220         if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) {
 221                 /* Have lock */
 222                 return 1;
 223         }
 224         return 0;
 225 }
 226 EXPORT_SYMBOL(drm_lock_take);
 227
 228 /**
 229  * This takes a lock forcibly and hands it to context.  Should ONLY be used
 230  * inside *_unlock to give lock to kernel before calling *_dma_schedule.
 231  *
 232  * \param dev DRM device.
 233  * \param lock lock pointer.
 234  * \param context locking context.
 235  * \return always one.
 236  *
 237  * Resets the lock file pointer.
 238  * Marks the lock as held by the given context, via the \p cmpxchg instruction.
 239  */
 240 static int drm_lock_transfer(struct drm_lock_data *lock_data,
 241                              unsigned int context)
 242 {
 243         unsigned int old, new, prev;
 244         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 245
 246         lock_data->file_priv = NULL;
 247         do {
 248                 old = *lock;
 249                 new = context | _DRM_LOCK_HELD;
 250                 prev = cmpxchg(lock, old, new);
 251         } while (prev != old);
 252         return 1;
 253 }
 254
 255 /**
 256  * Free lock.
 257  *
 258  * \param dev DRM device.
 259  * \param lock lock.
 260  * \param context context.
 261  *
 262  * Resets the lock file pointer.
 263  * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
 264  * waiting on the lock queue.
 265  */
 266 int drm_lock_free(struct drm_lock_data *lock_data, unsigned int context)
 267 {
 268         unsigned int old, new, prev;
 269         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 270
 271         spin_lock_bh(&lock_data->spinlock);
 272         if (lock_data->kernel_waiters != 0) {
 273                 drm_lock_transfer(lock_data, 0);
 274                 lock_data->idle_has_lock = 1;
 275                 spin_unlock_bh(&lock_data->spinlock);
 276                 return 1;
 277         }
 278         spin_unlock_bh(&lock_data->spinlock);
 279
 280         do {
 281                 old = *lock;
 282                 new = _DRM_LOCKING_CONTEXT(old);
 283                 prev = cmpxchg(lock, old, new);
 284         } while (prev != old);
 285
 286         if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
 287                 DRM_ERROR("%d freed heavyweight lock held by %d\n",
 288                           context, _DRM_LOCKING_CONTEXT(old));
 289                 return 1;
 290         }
 291         wake_up_interruptible(&lock_data->lock_queue);
 292         return 0;
 293 }
 294 EXPORT_SYMBOL(drm_lock_free);
 295
 296 /**
 297  * If we get here, it means that the process has called DRM_IOCTL_LOCK
 298  * without calling DRM_IOCTL_UNLOCK.
 299  *
 300  * If the lock is not held, then let the signal proceed as usual.  If the lock
 301  * is held, then set the contended flag and keep the signal blocked.
 302  *
 303  * \param priv pointer to a drm_sigdata structure.
 304  * \return one if the signal should be delivered normally, or zero if the
 305  * signal should be blocked.
 306  */
 307 static int drm_notifier(void *priv)
 308 {
 309         struct drm_sigdata *s = (struct drm_sigdata *) priv;
 310         unsigned int old, new, prev;
 311
 312         /* Allow signal delivery if lock isn't held */
 313         if (!s->lock || !_DRM_LOCK_IS_HELD(s->lock->lock)
 314             || _DRM_LOCKING_CONTEXT(s->lock->lock) != s->context)
 315                 return 1;
 316
 317         /* Otherwise, set flag to force call to
 318            drmUnlock */
 319         do {
 320                 old = s->lock->lock;
 321                 new = old | _DRM_LOCK_CONT;
 322                 prev = cmpxchg(&s->lock->lock, old, new);
 323         } while (prev != old);
 324         return 0;
 325 }
 326
 327 /**
 328  * This function returns immediately and takes the hw lock
 329  * with the kernel context if it is free, otherwise it gets the highest priority when and if
 330  * it is eventually released.
 331  *
 332  * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held
 333  * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause
 334  * a deadlock, which is why the "idlelock" was invented).
 335  *
 336  * This should be sufficient to wait for GPU idle without
 337  * having to worry about starvation.
 338  */
 339
 340 void drm_idlelock_take(struct drm_lock_data *lock_data)
 341 {
 342         int ret = 0;
 343
 344         spin_lock_bh(&lock_data->spinlock);
 345         lock_data->kernel_waiters++;
 346         if (!lock_data->idle_has_lock) {
 347
 348                 spin_unlock_bh(&lock_data->spinlock);
 349                 ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
 350                 spin_lock_bh(&lock_data->spinlock);
 351
 352                 if (ret == 1)
 353                         lock_data->idle_has_lock = 1;
 354         }
 355         spin_unlock_bh(&lock_data->spinlock);
 356 }
 357 EXPORT_SYMBOL(drm_idlelock_take);
 358
 359 void drm_idlelock_release(struct drm_lock_data *lock_data)
 360 {
 361         unsigned int old, prev;
 362         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 363
 364         spin_lock_bh(&lock_data->spinlock);
 365         if (--lock_data->kernel_waiters == 0) {
 366                 if (lock_data->idle_has_lock) {
 367                         do {
 368                                 old = *lock;
 369                                 prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT);
 370                         } while (prev != old);
 371                         wake_up_interruptible(&lock_data->lock_queue);
 372                         lock_data->idle_has_lock = 0;
 373                 }
 374         }
 375         spin_unlock_bh(&lock_data->spinlock);
 376 }
 377 EXPORT_SYMBOL(drm_idlelock_release);
 378
 379
 380 int drm_i_have_hw_lock(struct drm_device *dev, struct drm_file *file_priv)
 381 {
 382         return (file_priv->lock_count && dev->lock.hw_lock &&
 383                 _DRM_LOCK_IS_HELD(dev->lock.hw_lock->lock) &&
 384                 dev->lock.file_priv == file_priv);
 385 }
 386
 387 EXPORT_SYMBOL(drm_i_have_hw_lock);