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 <linux/export.h>
  37 #include <drm/drmP.h>
  38
  39 static int drm_notifier(void *priv);
  40
  41 static int drm_lock_take(struct drm_lock_data *lock_data, unsigned int context);
  42
  43 /**
  44  * Lock ioctl.
  45  *
  46  * \param inode device inode.
  47  * \param file_priv DRM file private.
  48  * \param cmd command.
  49  * \param arg user argument, pointing to a drm_lock structure.
  50  * \return zero on success or negative number on failure.
  51  *
  52  * Add the current task to the lock wait queue, and attempt to take to lock.
  53  */
  54 int drm_lock(struct drm_device *dev, void *data, struct drm_file *file_priv)
  55 {
  56         DECLARE_WAITQUEUE(entry, current);
  57         struct drm_lock *lock = data;
  58         struct drm_master *master = file_priv->master;
  59         int ret = 0;
  60
  61         ++file_priv->lock_count;
  62
  63         if (lock->context == DRM_KERNEL_CONTEXT) {
  64                 DRM_ERROR("Process %d using kernel context %d\n",
  65                           task_pid_nr(current), lock->context);
  66                 return -EINVAL;
  67         }
  68
  69         DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
  70                   lock->context, task_pid_nr(current),
  71                   master->lock.hw_lock->lock, lock->flags);
  72
  73         add_wait_queue(&master->lock.lock_queue, &entry);
  74         spin_lock_bh(&master->lock.spinlock);
  75         master->lock.user_waiters++;
  76         spin_unlock_bh(&master->lock.spinlock);
  77
  78         for (;;) {
  79                 __set_current_state(TASK_INTERRUPTIBLE);
  80                 if (!master->lock.hw_lock) {
  81                         /* Device has been unregistered */
  82                         send_sig(SIGTERM, current, 0);
  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                 mutex_unlock(&drm_global_mutex);
  95                 schedule();
  96                 mutex_lock(&drm_global_mutex);
  97                 if (signal_pending(current)) {
  98                         ret = -EINTR;
  99                         break;
 100                 }
 101         }
 102         spin_lock_bh(&master->lock.spinlock);
 103         master->lock.user_waiters--;
 104         spin_unlock_bh(&master->lock.spinlock);
 105         __set_current_state(TASK_RUNNING);
 106         remove_wait_queue(&master->lock.lock_queue, &entry);
 107
 108         DRM_DEBUG("%d %s\n", lock->context,
 109                   ret ? "interrupted" : "has lock");
 110         if (ret) return ret;
 111
 112         /* don't set the block all signals on the master process for now
 113          * really probably not the correct answer but lets us debug xkb
 114          * xserver for now */
 115         if (!file_priv->is_master) {
 116                 sigemptyset(&dev->sigmask);
 117                 sigaddset(&dev->sigmask, SIGSTOP);
 118                 sigaddset(&dev->sigmask, SIGTSTP);
 119                 sigaddset(&dev->sigmask, SIGTTIN);
 120                 sigaddset(&dev->sigmask, SIGTTOU);
 121                 dev->sigdata.context = lock->context;
 122                 dev->sigdata.lock = master->lock.hw_lock;
 123                 block_all_signals(drm_notifier, &dev->sigdata, &dev->sigmask);
 124         }
 125
 126         if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT))
 127         {
 128                 if (dev->driver->dma_quiescent(dev)) {
 129                         DRM_DEBUG("%d waiting for DMA quiescent\n",
 130                                   lock->context);
 131                         return -EBUSY;
 132                 }
 133         }
 134
 135         return 0;
 136 }
 137
 138 /**
 139  * Unlock ioctl.
 140  *
 141  * \param inode device inode.
 142  * \param file_priv DRM file private.
 143  * \param cmd command.
 144  * \param arg user argument, pointing to a drm_lock structure.
 145  * \return zero on success or negative number on failure.
 146  *
 147  * Transfer and free the lock.
 148  */
 149 int drm_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv)
 150 {
 151         struct drm_lock *lock = data;
 152         struct drm_master *master = file_priv->master;
 153
 154         if (lock->context == DRM_KERNEL_CONTEXT) {
 155                 DRM_ERROR("Process %d using kernel context %d\n",
 156                           task_pid_nr(current), lock->context);
 157                 return -EINVAL;
 158         }
 159
 160         atomic_inc(&dev->counts[_DRM_STAT_UNLOCKS]);
 161
 162         if (drm_lock_free(&master->lock, lock->context)) {
 163                 /* FIXME: Should really bail out here. */
 164         }
 165
 166         unblock_all_signals();
 167         return 0;
 168 }
 169
 170 /**
 171  * Take the heavyweight lock.
 172  *
 173  * \param lock lock pointer.
 174  * \param context locking context.
 175  * \return one if the lock is held, or zero otherwise.
 176  *
 177  * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
 178  */
 179 static
 180 int drm_lock_take(struct drm_lock_data *lock_data,
 181                   unsigned int context)
 182 {
 183         unsigned int old, new, prev;
 184         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 185
 186         spin_lock_bh(&lock_data->spinlock);
 187         do {
 188                 old = *lock;
 189                 if (old & _DRM_LOCK_HELD)
 190                         new = old | _DRM_LOCK_CONT;
 191                 else {
 192                         new = context | _DRM_LOCK_HELD |
 193                                 ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
 194                                  _DRM_LOCK_CONT : 0);
 195                 }
 196                 prev = cmpxchg(lock, old, new);
 197         } while (prev != old);
 198         spin_unlock_bh(&lock_data->spinlock);
 199
 200         if (_DRM_LOCKING_CONTEXT(old) == context) {
 201                 if (old & _DRM_LOCK_HELD) {
 202                         if (context != DRM_KERNEL_CONTEXT) {
 203                                 DRM_ERROR("%d holds heavyweight lock\n",
 204                                           context);
 205                         }
 206                         return 0;
 207                 }
 208         }
 209
 210         if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) {
 211                 /* Have lock */
 212                 return 1;
 213         }
 214         return 0;
 215 }
 216
 217 /**
 218  * This takes a lock forcibly and hands it to context.  Should ONLY be used
 219  * inside *_unlock to give lock to kernel before calling *_dma_schedule.
 220  *
 221  * \param dev DRM device.
 222  * \param lock lock pointer.
 223  * \param context locking context.
 224  * \return always one.
 225  *
 226  * Resets the lock file pointer.
 227  * Marks the lock as held by the given context, via the \p cmpxchg instruction.
 228  */
 229 static int drm_lock_transfer(struct drm_lock_data *lock_data,
 230                              unsigned int context)
 231 {
 232         unsigned int old, new, prev;
 233         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 234
 235         lock_data->file_priv = NULL;
 236         do {
 237                 old = *lock;
 238                 new = context | _DRM_LOCK_HELD;
 239                 prev = cmpxchg(lock, old, new);
 240         } while (prev != old);
 241         return 1;
 242 }
 243
 244 /**
 245  * Free lock.
 246  *
 247  * \param dev DRM device.
 248  * \param lock lock.
 249  * \param context context.
 250  *
 251  * Resets the lock file pointer.
 252  * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
 253  * waiting on the lock queue.
 254  */
 255 int drm_lock_free(struct drm_lock_data *lock_data, unsigned int context)
 256 {
 257         unsigned int old, new, prev;
 258         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 259
 260         spin_lock_bh(&lock_data->spinlock);
 261         if (lock_data->kernel_waiters != 0) {
 262                 drm_lock_transfer(lock_data, 0);
 263                 lock_data->idle_has_lock = 1;
 264                 spin_unlock_bh(&lock_data->spinlock);
 265                 return 1;
 266         }
 267         spin_unlock_bh(&lock_data->spinlock);
 268
 269         do {
 270                 old = *lock;
 271                 new = _DRM_LOCKING_CONTEXT(old);
 272                 prev = cmpxchg(lock, old, new);
 273         } while (prev != old);
 274
 275         if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
 276                 DRM_ERROR("%d freed heavyweight lock held by %d\n",
 277                           context, _DRM_LOCKING_CONTEXT(old));
 278                 return 1;
 279         }
 280         wake_up_interruptible(&lock_data->lock_queue);
 281         return 0;
 282 }
 283
 284 /**
 285  * If we get here, it means that the process has called DRM_IOCTL_LOCK
 286  * without calling DRM_IOCTL_UNLOCK.
 287  *
 288  * If the lock is not held, then let the signal proceed as usual.  If the lock
 289  * is held, then set the contended flag and keep the signal blocked.
 290  *
 291  * \param priv pointer to a drm_sigdata structure.
 292  * \return one if the signal should be delivered normally, or zero if the
 293  * signal should be blocked.
 294  */
 295 static int drm_notifier(void *priv)
 296 {
 297         struct drm_sigdata *s = (struct drm_sigdata *) priv;
 298         unsigned int old, new, prev;
 299
 300         /* Allow signal delivery if lock isn't held */
 301         if (!s->lock || !_DRM_LOCK_IS_HELD(s->lock->lock)
 302             || _DRM_LOCKING_CONTEXT(s->lock->lock) != s->context)
 303                 return 1;
 304
 305         /* Otherwise, set flag to force call to
 306            drmUnlock */
 307         do {
 308                 old = s->lock->lock;
 309                 new = old | _DRM_LOCK_CONT;
 310                 prev = cmpxchg(&s->lock->lock, old, new);
 311         } while (prev != old);
 312         return 0;
 313 }
 314
 315 /**
 316  * This function returns immediately and takes the hw lock
 317  * with the kernel context if it is free, otherwise it gets the highest priority when and if
 318  * it is eventually released.
 319  *
 320  * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held
 321  * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause
 322  * a deadlock, which is why the "idlelock" was invented).
 323  *
 324  * This should be sufficient to wait for GPU idle without
 325  * having to worry about starvation.
 326  */
 327
 328 void drm_idlelock_take(struct drm_lock_data *lock_data)
 329 {
 330         int ret;
 331
 332         spin_lock_bh(&lock_data->spinlock);
 333         lock_data->kernel_waiters++;
 334         if (!lock_data->idle_has_lock) {
 335
 336                 spin_unlock_bh(&lock_data->spinlock);
 337                 ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
 338                 spin_lock_bh(&lock_data->spinlock);
 339
 340                 if (ret == 1)
 341                         lock_data->idle_has_lock = 1;
 342         }
 343         spin_unlock_bh(&lock_data->spinlock);
 344 }
 345 EXPORT_SYMBOL(drm_idlelock_take);
 346
 347 void drm_idlelock_release(struct drm_lock_data *lock_data)
 348 {
 349         unsigned int old, prev;
 350         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 351
 352         spin_lock_bh(&lock_data->spinlock);
 353         if (--lock_data->kernel_waiters == 0) {
 354                 if (lock_data->idle_has_lock) {
 355                         do {
 356                                 old = *lock;
 357                                 prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT);
 358                         } while (prev != old);
 359                         wake_up_interruptible(&lock_data->lock_queue);
 360                         lock_data->idle_has_lock = 0;
 361                 }
 362         }
 363         spin_unlock_bh(&lock_data->spinlock);
 364 }
 365 EXPORT_SYMBOL(drm_idlelock_release);
 366
 367 int drm_i_have_hw_lock(struct drm_device *dev, struct drm_file *file_priv)
 368 {
 369         struct drm_master *master = file_priv->master;
 370         return (file_priv->lock_count && master->lock.hw_lock &&
 371                 _DRM_LOCK_IS_HELD(master->lock.hw_lock->lock) &&
 372                 master->lock.file_priv == file_priv);
 373 }