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 static int drm_lock_take(struct drm_lock_data *lock_data, unsigned int context);
  41
  42 /**
  43  * Lock ioctl.
  44  *
  45  * \param inode device inode.
  46  * \param file_priv DRM file private.
  47  * \param cmd command.
  48  * \param arg user argument, pointing to a drm_lock structure.
  49  * \return zero on success or negative number on failure.
  50  *
  51  * Add the current task to the lock wait queue, and attempt to take to lock.
  52  */
  53 int drm_lock(struct drm_device *dev, void *data, struct drm_file *file_priv)
  54 {
  55         DECLARE_WAITQUEUE(entry, current);
  56         struct drm_lock *lock = data;
  57         struct drm_master *master = file_priv->master;
  58         int ret = 0;
  59
  60         ++file_priv->lock_count;
  61
  62         if (lock->context == DRM_KERNEL_CONTEXT) {
  63                 DRM_ERROR("Process %d using kernel context %d\n",
  64                           task_pid_nr(current), lock->context);
  65                 return -EINVAL;
  66         }
  67
  68         DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
  69                   lock->context, task_pid_nr(current),
  70                   master->lock.hw_lock->lock, lock->flags);
  71
  72         if (drm_core_check_feature(dev, DRIVER_DMA_QUEUE))
  73                 if (lock->context < 0)
  74                         return -EINVAL;
  75
  76         add_wait_queue(&master->lock.lock_queue, &entry);
  77         spin_lock_bh(&master->lock.spinlock);
  78         master->lock.user_waiters++;
  79         spin_unlock_bh(&master->lock.spinlock);
  80
  81         for (;;) {
  82                 __set_current_state(TASK_INTERRUPTIBLE);
  83                 if (!master->lock.hw_lock) {
  84                         /* Device has been unregistered */
  85                         send_sig(SIGTERM, current, 0);
  86                         ret = -EINTR;
  87                         break;
  88                 }
  89                 if (drm_lock_take(&master->lock, lock->context)) {
  90                         master->lock.file_priv = file_priv;
  91                         master->lock.lock_time = jiffies;
  92                         atomic_inc(&dev->counts[_DRM_STAT_LOCKS]);
  93                         break;  /* Got lock */
  94                 }
  95
  96                 /* Contention */
  97                 mutex_unlock(&drm_global_mutex);
  98                 schedule();
  99                 mutex_lock(&drm_global_mutex);
 100                 if (signal_pending(current)) {
 101                         ret = -EINTR;
 102                         break;
 103                 }
 104         }
 105         spin_lock_bh(&master->lock.spinlock);
 106         master->lock.user_waiters--;
 107         spin_unlock_bh(&master->lock.spinlock);
 108         __set_current_state(TASK_RUNNING);
 109         remove_wait_queue(&master->lock.lock_queue, &entry);
 110
 111         DRM_DEBUG("%d %s\n", lock->context,
 112                   ret ? "interrupted" : "has lock");
 113         if (ret) return ret;
 114
 115         /* don't set the block all signals on the master process for now
 116          * really probably not the correct answer but lets us debug xkb
 117          * xserver for now */
 118         if (!file_priv->is_master) {
 119                 sigemptyset(&dev->sigmask);
 120                 sigaddset(&dev->sigmask, SIGSTOP);
 121                 sigaddset(&dev->sigmask, SIGTSTP);
 122                 sigaddset(&dev->sigmask, SIGTTIN);
 123                 sigaddset(&dev->sigmask, SIGTTOU);
 124                 dev->sigdata.context = lock->context;
 125                 dev->sigdata.lock = master->lock.hw_lock;
 126                 block_all_signals(drm_notifier, &dev->sigdata, &dev->sigmask);
 127         }
 128
 129         if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT))
 130         {
 131                 if (dev->driver->dma_quiescent(dev)) {
 132                         DRM_DEBUG("%d waiting for DMA quiescent\n",
 133                                   lock->context);
 134                         return -EBUSY;
 135                 }
 136         }
 137
 138         return 0;
 139 }
 140
 141 /**
 142  * Unlock ioctl.
 143  *
 144  * \param inode device inode.
 145  * \param file_priv DRM file private.
 146  * \param cmd command.
 147  * \param arg user argument, pointing to a drm_lock structure.
 148  * \return zero on success or negative number on failure.
 149  *
 150  * Transfer and free the lock.
 151  */
 152 int drm_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv)
 153 {
 154         struct drm_lock *lock = data;
 155         struct drm_master *master = file_priv->master;
 156
 157         if (lock->context == DRM_KERNEL_CONTEXT) {
 158                 DRM_ERROR("Process %d using kernel context %d\n",
 159                           task_pid_nr(current), lock->context);
 160                 return -EINVAL;
 161         }
 162
 163         atomic_inc(&dev->counts[_DRM_STAT_UNLOCKS]);
 164
 165         if (drm_lock_free(&master->lock, lock->context)) {
 166                 /* FIXME: Should really bail out here. */
 167         }
 168
 169         unblock_all_signals();
 170         return 0;
 171 }
 172
 173 /**
 174  * Take the heavyweight lock.
 175  *
 176  * \param lock lock pointer.
 177  * \param context locking context.
 178  * \return one if the lock is held, or zero otherwise.
 179  *
 180  * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
 181  */
 182 static
 183 int drm_lock_take(struct drm_lock_data *lock_data,
 184                   unsigned int context)
 185 {
 186         unsigned int old, new, prev;
 187         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 188
 189         spin_lock_bh(&lock_data->spinlock);
 190         do {
 191                 old = *lock;
 192                 if (old & _DRM_LOCK_HELD)
 193                         new = old | _DRM_LOCK_CONT;
 194                 else {
 195                         new = context | _DRM_LOCK_HELD |
 196                                 ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
 197                                  _DRM_LOCK_CONT : 0);
 198                 }
 199                 prev = cmpxchg(lock, old, new);
 200         } while (prev != old);
 201         spin_unlock_bh(&lock_data->spinlock);
 202
 203         if (_DRM_LOCKING_CONTEXT(old) == context) {
 204                 if (old & _DRM_LOCK_HELD) {
 205                         if (context != DRM_KERNEL_CONTEXT) {
 206                                 DRM_ERROR("%d holds heavyweight lock\n",
 207                                           context);
 208                         }
 209                         return 0;
 210                 }
 211         }
 212
 213         if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) {
 214                 /* Have lock */
 215                 return 1;
 216         }
 217         return 0;
 218 }
 219
 220 /**
 221  * This takes a lock forcibly and hands it to context.  Should ONLY be used
 222  * inside *_unlock to give lock to kernel before calling *_dma_schedule.
 223  *
 224  * \param dev DRM device.
 225  * \param lock lock pointer.
 226  * \param context locking context.
 227  * \return always one.
 228  *
 229  * Resets the lock file pointer.
 230  * Marks the lock as held by the given context, via the \p cmpxchg instruction.
 231  */
 232 static int drm_lock_transfer(struct drm_lock_data *lock_data,
 233                              unsigned int context)
 234 {
 235         unsigned int old, new, prev;
 236         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 237
 238         lock_data->file_priv = NULL;
 239         do {
 240                 old = *lock;
 241                 new = context | _DRM_LOCK_HELD;
 242                 prev = cmpxchg(lock, old, new);
 243         } while (prev != old);
 244         return 1;
 245 }
 246
 247 /**
 248  * Free lock.
 249  *
 250  * \param dev DRM device.
 251  * \param lock lock.
 252  * \param context context.
 253  *
 254  * Resets the lock file pointer.
 255  * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
 256  * waiting on the lock queue.
 257  */
 258 int drm_lock_free(struct drm_lock_data *lock_data, unsigned int context)
 259 {
 260         unsigned int old, new, prev;
 261         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 262
 263         spin_lock_bh(&lock_data->spinlock);
 264         if (lock_data->kernel_waiters != 0) {
 265                 drm_lock_transfer(lock_data, 0);
 266                 lock_data->idle_has_lock = 1;
 267                 spin_unlock_bh(&lock_data->spinlock);
 268                 return 1;
 269         }
 270         spin_unlock_bh(&lock_data->spinlock);
 271
 272         do {
 273                 old = *lock;
 274                 new = _DRM_LOCKING_CONTEXT(old);
 275                 prev = cmpxchg(lock, old, new);
 276         } while (prev != old);
 277
 278         if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
 279                 DRM_ERROR("%d freed heavyweight lock held by %d\n",
 280                           context, _DRM_LOCKING_CONTEXT(old));
 281                 return 1;
 282         }
 283         wake_up_interruptible(&lock_data->lock_queue);
 284         return 0;
 285 }
 286
 287 /**
 288  * If we get here, it means that the process has called DRM_IOCTL_LOCK
 289  * without calling DRM_IOCTL_UNLOCK.
 290  *
 291  * If the lock is not held, then let the signal proceed as usual.  If the lock
 292  * is held, then set the contended flag and keep the signal blocked.
 293  *
 294  * \param priv pointer to a drm_sigdata structure.
 295  * \return one if the signal should be delivered normally, or zero if the
 296  * signal should be blocked.
 297  */
 298 static int drm_notifier(void *priv)
 299 {
 300         struct drm_sigdata *s = (struct drm_sigdata *) priv;
 301         unsigned int old, new, prev;
 302
 303         /* Allow signal delivery if lock isn't held */
 304         if (!s->lock || !_DRM_LOCK_IS_HELD(s->lock->lock)
 305             || _DRM_LOCKING_CONTEXT(s->lock->lock) != s->context)
 306                 return 1;
 307
 308         /* Otherwise, set flag to force call to
 309            drmUnlock */
 310         do {
 311                 old = s->lock->lock;
 312                 new = old | _DRM_LOCK_CONT;
 313                 prev = cmpxchg(&s->lock->lock, old, new);
 314         } while (prev != old);
 315         return 0;
 316 }
 317
 318 /**
 319  * This function returns immediately and takes the hw lock
 320  * with the kernel context if it is free, otherwise it gets the highest priority when and if
 321  * it is eventually released.
 322  *
 323  * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held
 324  * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause
 325  * a deadlock, which is why the "idlelock" was invented).
 326  *
 327  * This should be sufficient to wait for GPU idle without
 328  * having to worry about starvation.
 329  */
 330
 331 void drm_idlelock_take(struct drm_lock_data *lock_data)
 332 {
 333         int ret = 0;
 334
 335         spin_lock_bh(&lock_data->spinlock);
 336         lock_data->kernel_waiters++;
 337         if (!lock_data->idle_has_lock) {
 338
 339                 spin_unlock_bh(&lock_data->spinlock);
 340                 ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
 341                 spin_lock_bh(&lock_data->spinlock);
 342
 343                 if (ret == 1)
 344                         lock_data->idle_has_lock = 1;
 345         }
 346         spin_unlock_bh(&lock_data->spinlock);
 347 }
 348
 349 void drm_idlelock_release(struct drm_lock_data *lock_data)
 350 {
 351         unsigned int old, prev;
 352         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 353
 354         spin_lock_bh(&lock_data->spinlock);
 355         if (--lock_data->kernel_waiters == 0) {
 356                 if (lock_data->idle_has_lock) {
 357                         do {
 358                                 old = *lock;
 359                                 prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT);
 360                         } while (prev != old);
 361                         wake_up_interruptible(&lock_data->lock_queue);
 362                         lock_data->idle_has_lock = 0;
 363                 }
 364         }
 365         spin_unlock_bh(&lock_data->spinlock);
 366 }
 367
 368 int drm_i_have_hw_lock(struct drm_device *dev, struct drm_file *file_priv)
 369 {
 370         struct drm_master *master = file_priv->master;
 371         return (file_priv->lock_count && master->lock.hw_lock &&
 372                 _DRM_LOCK_IS_HELD(master->lock.hw_lock->lock) &&
 373                 master->lock.file_priv == file_priv);
 374 }