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 #include "drm_legacy.h"
  39 #include "drm_internal.h"
  40
  41 static int drm_notifier(void *priv);
  42
  43 static int drm_lock_take(struct drm_lock_data *lock_data, unsigned int context);
  44
  45 /**
  46  * Lock ioctl.
  47  *
  48  * \param inode device inode.
  49  * \param file_priv DRM file private.
  50  * \param cmd command.
  51  * \param arg user argument, pointing to a drm_lock structure.
  52  * \return zero on success or negative number on failure.
  53  *
  54  * Add the current task to the lock wait queue, and attempt to take to lock.
  55  */
  56 int drm_legacy_lock(struct drm_device *dev, void *data,
  57                     struct drm_file *file_priv)
  58 {
  59         DECLARE_WAITQUEUE(entry, current);
  60         struct drm_lock *lock = data;
  61         struct drm_master *master = file_priv->master;
  62         int ret = 0;
  63
  64         if (drm_core_check_feature(dev, DRIVER_MODESET))
  65                 return -EINVAL;
  66
  67         ++file_priv->lock_count;
  68
  69         if (lock->context == DRM_KERNEL_CONTEXT) {
  70                 DRM_ERROR("Process %d using kernel context %d\n",
  71                           task_pid_nr(current), lock->context);
  72                 return -EINVAL;
  73         }
  74
  75         DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
  76                   lock->context, task_pid_nr(current),
  77                   master->lock.hw_lock->lock, lock->flags);
  78
  79         add_wait_queue(&master->lock.lock_queue, &entry);
  80         spin_lock_bh(&master->lock.spinlock);
  81         master->lock.user_waiters++;
  82         spin_unlock_bh(&master->lock.spinlock);
  83
  84         for (;;) {
  85                 __set_current_state(TASK_INTERRUPTIBLE);
  86                 if (!master->lock.hw_lock) {
  87                         /* Device has been unregistered */
  88                         send_sig(SIGTERM, current, 0);
  89                         ret = -EINTR;
  90                         break;
  91                 }
  92                 if (drm_lock_take(&master->lock, lock->context)) {
  93                         master->lock.file_priv = file_priv;
  94                         master->lock.lock_time = jiffies;
  95                         break;  /* Got lock */
  96                 }
  97
  98                 /* Contention */
  99                 mutex_unlock(&drm_global_mutex);
 100                 schedule();
 101                 mutex_lock(&drm_global_mutex);
 102                 if (signal_pending(current)) {
 103                         ret = -EINTR;
 104                         break;
 105                 }
 106         }
 107         spin_lock_bh(&master->lock.spinlock);
 108         master->lock.user_waiters--;
 109         spin_unlock_bh(&master->lock.spinlock);
 110         __set_current_state(TASK_RUNNING);
 111         remove_wait_queue(&master->lock.lock_queue, &entry);
 112
 113         DRM_DEBUG("%d %s\n", lock->context,
 114                   ret ? "interrupted" : "has lock");
 115         if (ret) return ret;
 116
 117         /* don't set the block all signals on the master process for now
 118          * really probably not the correct answer but lets us debug xkb
 119          * xserver for now */
 120         if (!file_priv->is_master) {
 121                 sigemptyset(&dev->sigmask);
 122                 sigaddset(&dev->sigmask, SIGSTOP);
 123                 sigaddset(&dev->sigmask, SIGTSTP);
 124                 sigaddset(&dev->sigmask, SIGTTIN);
 125                 sigaddset(&dev->sigmask, SIGTTOU);
 126                 dev->sigdata.context = lock->context;
 127                 dev->sigdata.lock = master->lock.hw_lock;
 128                 block_all_signals(drm_notifier, dev, &dev->sigmask);
 129         }
 130
 131         if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT))
 132         {
 133                 if (dev->driver->dma_quiescent(dev)) {
 134                         DRM_DEBUG("%d waiting for DMA quiescent\n",
 135                                   lock->context);
 136                         return -EBUSY;
 137                 }
 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_legacy_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv)
 155 {
 156         struct drm_lock *lock = data;
 157         struct drm_master *master = file_priv->master;
 158
 159         if (drm_core_check_feature(dev, DRIVER_MODESET))
 160                 return -EINVAL;
 161
 162         if (lock->context == DRM_KERNEL_CONTEXT) {
 163                 DRM_ERROR("Process %d using kernel context %d\n",
 164                           task_pid_nr(current), lock->context);
 165                 return -EINVAL;
 166         }
 167
 168         if (drm_legacy_lock_free(&master->lock, lock->context)) {
 169                 /* FIXME: Should really bail out here. */
 170         }
 171
 172         unblock_all_signals();
 173         return 0;
 174 }
 175
 176 /**
 177  * Take the heavyweight lock.
 178  *
 179  * \param lock lock pointer.
 180  * \param context locking context.
 181  * \return one if the lock is held, or zero otherwise.
 182  *
 183  * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
 184  */
 185 static
 186 int drm_lock_take(struct drm_lock_data *lock_data,
 187                   unsigned int context)
 188 {
 189         unsigned int old, new, prev;
 190         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 191
 192         spin_lock_bh(&lock_data->spinlock);
 193         do {
 194                 old = *lock;
 195                 if (old & _DRM_LOCK_HELD)
 196                         new = old | _DRM_LOCK_CONT;
 197                 else {
 198                         new = context | _DRM_LOCK_HELD |
 199                                 ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
 200                                  _DRM_LOCK_CONT : 0);
 201                 }
 202                 prev = cmpxchg(lock, old, new);
 203         } while (prev != old);
 204         spin_unlock_bh(&lock_data->spinlock);
 205
 206         if (_DRM_LOCKING_CONTEXT(old) == context) {
 207                 if (old & _DRM_LOCK_HELD) {
 208                         if (context != DRM_KERNEL_CONTEXT) {
 209                                 DRM_ERROR("%d holds heavyweight lock\n",
 210                                           context);
 211                         }
 212                         return 0;
 213                 }
 214         }
 215
 216         if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) {
 217                 /* Have lock */
 218                 return 1;
 219         }
 220         return 0;
 221 }
 222
 223 /**
 224  * This takes a lock forcibly and hands it to context.  Should ONLY be used
 225  * inside *_unlock to give lock to kernel before calling *_dma_schedule.
 226  *
 227  * \param dev DRM device.
 228  * \param lock lock pointer.
 229  * \param context locking context.
 230  * \return always one.
 231  *
 232  * Resets the lock file pointer.
 233  * Marks the lock as held by the given context, via the \p cmpxchg instruction.
 234  */
 235 static int drm_lock_transfer(struct drm_lock_data *lock_data,
 236                              unsigned int context)
 237 {
 238         unsigned int old, new, prev;
 239         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 240
 241         lock_data->file_priv = NULL;
 242         do {
 243                 old = *lock;
 244                 new = context | _DRM_LOCK_HELD;
 245                 prev = cmpxchg(lock, old, new);
 246         } while (prev != old);
 247         return 1;
 248 }
 249
 250 /**
 251  * Free lock.
 252  *
 253  * \param dev DRM device.
 254  * \param lock lock.
 255  * \param context context.
 256  *
 257  * Resets the lock file pointer.
 258  * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
 259  * waiting on the lock queue.
 260  */
 261 int drm_legacy_lock_free(struct drm_lock_data *lock_data, unsigned int context)
 262 {
 263         unsigned int old, new, prev;
 264         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 265
 266         spin_lock_bh(&lock_data->spinlock);
 267         if (lock_data->kernel_waiters != 0) {
 268                 drm_lock_transfer(lock_data, 0);
 269                 lock_data->idle_has_lock = 1;
 270                 spin_unlock_bh(&lock_data->spinlock);
 271                 return 1;
 272         }
 273         spin_unlock_bh(&lock_data->spinlock);
 274
 275         do {
 276                 old = *lock;
 277                 new = _DRM_LOCKING_CONTEXT(old);
 278                 prev = cmpxchg(lock, old, new);
 279         } while (prev != old);
 280
 281         if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
 282                 DRM_ERROR("%d freed heavyweight lock held by %d\n",
 283                           context, _DRM_LOCKING_CONTEXT(old));
 284                 return 1;
 285         }
 286         wake_up_interruptible(&lock_data->lock_queue);
 287         return 0;
 288 }
 289
 290 /**
 291  * If we get here, it means that the process has called DRM_IOCTL_LOCK
 292  * without calling DRM_IOCTL_UNLOCK.
 293  *
 294  * If the lock is not held, then let the signal proceed as usual.  If the lock
 295  * is held, then set the contended flag and keep the signal blocked.
 296  *
 297  * \param priv pointer to a drm_device structure.
 298  * \return one if the signal should be delivered normally, or zero if the
 299  * signal should be blocked.
 300  */
 301 static int drm_notifier(void *priv)
 302 {
 303         struct drm_device *dev = priv;
 304         struct drm_hw_lock *lock = dev->sigdata.lock;
 305         unsigned int old, new, prev;
 306
 307         /* Allow signal delivery if lock isn't held */
 308         if (!lock || !_DRM_LOCK_IS_HELD(lock->lock)
 309             || _DRM_LOCKING_CONTEXT(lock->lock) != dev->sigdata.context)
 310                 return 1;
 311
 312         /* Otherwise, set flag to force call to
 313            drmUnlock */
 314         do {
 315                 old = lock->lock;
 316                 new = old | _DRM_LOCK_CONT;
 317                 prev = cmpxchg(&lock->lock, old, new);
 318         } while (prev != old);
 319         return 0;
 320 }
 321
 322 /**
 323  * This function returns immediately and takes the hw lock
 324  * with the kernel context if it is free, otherwise it gets the highest priority when and if
 325  * it is eventually released.
 326  *
 327  * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held
 328  * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause
 329  * a deadlock, which is why the "idlelock" was invented).
 330  *
 331  * This should be sufficient to wait for GPU idle without
 332  * having to worry about starvation.
 333  */
 334
 335 void drm_legacy_idlelock_take(struct drm_lock_data *lock_data)
 336 {
 337         int ret;
 338
 339         spin_lock_bh(&lock_data->spinlock);
 340         lock_data->kernel_waiters++;
 341         if (!lock_data->idle_has_lock) {
 342
 343                 spin_unlock_bh(&lock_data->spinlock);
 344                 ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
 345                 spin_lock_bh(&lock_data->spinlock);
 346
 347                 if (ret == 1)
 348                         lock_data->idle_has_lock = 1;
 349         }
 350         spin_unlock_bh(&lock_data->spinlock);
 351 }
 352 EXPORT_SYMBOL(drm_legacy_idlelock_take);
 353
 354 void drm_legacy_idlelock_release(struct drm_lock_data *lock_data)
 355 {
 356         unsigned int old, prev;
 357         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 358
 359         spin_lock_bh(&lock_data->spinlock);
 360         if (--lock_data->kernel_waiters == 0) {
 361                 if (lock_data->idle_has_lock) {
 362                         do {
 363                                 old = *lock;
 364                                 prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT);
 365                         } while (prev != old);
 366                         wake_up_interruptible(&lock_data->lock_queue);
 367                         lock_data->idle_has_lock = 0;
 368                 }
 369         }
 370         spin_unlock_bh(&lock_data->spinlock);
 371 }
 372 EXPORT_SYMBOL(drm_legacy_idlelock_release);
 373
 374 int drm_legacy_i_have_hw_lock(struct drm_device *dev,
 375                               struct drm_file *file_priv)
 376 {
 377         struct drm_master *master = file_priv->master;
 378         return (file_priv->lock_count && master->lock.hw_lock &&
 379                 _DRM_LOCK_IS_HELD(master->lock.hw_lock->lock) &&
 380                 master->lock.file_priv == file_priv);
 381 }