sys/dev/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 <linux/sched/signal.h>
  38
  39 #include <drm/drmP.h>
  40 #include "drm_legacy.h"
  41 #include "drm_internal.h"
  42
  43 #if 0
  44 static int drm_lock_take(struct drm_lock_data *lock_data, unsigned int context);
  45
  46 /**
  47  * Take the heavyweight lock.
  48  *
  49  * \param lock lock pointer.
  50  * \param context locking context.
  51  * \return one if the lock is held, or zero otherwise.
  52  *
  53  * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
  54  */
  55 static
  56 int drm_lock_take(struct drm_lock_data *lock_data,
  57                   unsigned int context)
  58 {
  59         unsigned int old, new, prev;
  60         volatile unsigned int *lock = &lock_data->hw_lock->lock;
  61
  62         spin_lock_bh(&lock_data->spinlock);
  63         do {
  64                 old = *lock;
  65                 if (old & _DRM_LOCK_HELD)
  66                         new = old | _DRM_LOCK_CONT;
  67                 else {
  68                         new = context | _DRM_LOCK_HELD |
  69                                 ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
  70                                  _DRM_LOCK_CONT : 0);
  71                 }
  72                 prev = cmpxchg(lock, old, new);
  73         } while (prev != old);
  74         spin_unlock_bh(&lock_data->spinlock);
  75
  76         if (_DRM_LOCKING_CONTEXT(old) == context) {
  77                 if (old & _DRM_LOCK_HELD) {
  78                         if (context != DRM_KERNEL_CONTEXT) {
  79                                 DRM_ERROR("%d holds heavyweight lock\n",
  80                                           context);
  81                         }
  82                         return 0;
  83                 }
  84         }
  85
  86         if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) {
  87                 /* Have lock */
  88                 return 1;
  89         }
  90         return 0;
  91 }
  92
  93 /**
  94  * This takes a lock forcibly and hands it to context.  Should ONLY be used
  95  * inside *_unlock to give lock to kernel before calling *_dma_schedule.
  96  *
  97  * \param dev DRM device.
  98  * \param lock lock pointer.
  99  * \param context locking context.
 100  * \return always one.
 101  *
 102  * Resets the lock file pointer.
 103  * Marks the lock as held by the given context, via the \p cmpxchg instruction.
 104  */
 105 static int drm_lock_transfer(struct drm_lock_data *lock_data,
 106                              unsigned int context)
 107 {
 108         unsigned int old, new, prev;
 109         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 110
 111         lock_data->file_priv = NULL;
 112         do {
 113                 old = *lock;
 114                 new = context | _DRM_LOCK_HELD;
 115                 prev = cmpxchg(lock, old, new);
 116         } while (prev != old);
 117         return 1;
 118 }
 119
 120 static int drm_legacy_lock_free(struct drm_lock_data *lock_data,
 121                                 unsigned int context)
 122 {
 123         unsigned int old, new, prev;
 124         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 125
 126         spin_lock_bh(&lock_data->spinlock);
 127         if (lock_data->kernel_waiters != 0) {
 128                 drm_lock_transfer(lock_data, 0);
 129                 lock_data->idle_has_lock = 1;
 130                 spin_unlock_bh(&lock_data->spinlock);
 131                 return 1;
 132         }
 133         spin_unlock_bh(&lock_data->spinlock);
 134
 135         do {
 136                 old = *lock;
 137                 new = _DRM_LOCKING_CONTEXT(old);
 138                 prev = cmpxchg(lock, old, new);
 139         } while (prev != old);
 140
 141         if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
 142                 DRM_ERROR("%d freed heavyweight lock held by %d\n",
 143                           context, _DRM_LOCKING_CONTEXT(old));
 144                 return 1;
 145         }
 146         wake_up_interruptible(&lock_data->lock_queue);
 147         return 0;
 148 }
 149 #endif
 150
 151 /**
 152  * Lock ioctl.
 153  *
 154  * \param inode device inode.
 155  * \param file_priv DRM file private.
 156  * \param cmd command.
 157  * \param arg user argument, pointing to a drm_lock structure.
 158  * \return zero on success or negative number on failure.
 159  *
 160  * Add the current task to the lock wait queue, and attempt to take to lock.
 161  */
 162 int drm_legacy_lock(struct drm_device *dev, void *data,
 163                     struct drm_file *file_priv)
 164 {
 165 #if 0
 166         DECLARE_WAITQUEUE(entry, current);
 167         struct drm_lock *lock = data;
 168         struct drm_master *master = file_priv->master;
 169         int ret = 0;
 170
 171         if (!drm_core_check_feature(dev, DRIVER_LEGACY))
 172                 return -EINVAL;
 173
 174         ++file_priv->lock_count;
 175
 176         if (lock->context == DRM_KERNEL_CONTEXT) {
 177                 DRM_ERROR("Process %d using kernel context %d\n",
 178                           task_pid_nr(current), lock->context);
 179                 return -EINVAL;
 180         }
 181
 182         DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
 183                   lock->context, task_pid_nr(current),
 184                   master->lock.hw_lock ? master->lock.hw_lock->lock : -1,
 185                   lock->flags);
 186
 187         add_wait_queue(&master->lock.lock_queue, &entry);
 188         spin_lock_bh(&master->lock.spinlock);
 189         master->lock.user_waiters++;
 190         spin_unlock_bh(&master->lock.spinlock);
 191
 192         for (;;) {
 193                 __set_current_state(TASK_INTERRUPTIBLE);
 194                 if (!master->lock.hw_lock) {
 195                         /* Device has been unregistered */
 196                         send_sig(SIGTERM, current, 0);
 197                         ret = -EINTR;
 198                         break;
 199                 }
 200                 if (drm_lock_take(&master->lock, lock->context)) {
 201                         master->lock.file_priv = file_priv;
 202                         master->lock.lock_time = jiffies;
 203                         break;  /* Got lock */
 204                 }
 205
 206                 /* Contention */
 207                 mutex_unlock(&drm_global_mutex);
 208                 schedule();
 209                 mutex_lock(&drm_global_mutex);
 210                 if (signal_pending(current)) {
 211                         ret = -EINTR;
 212                         break;
 213                 }
 214         }
 215         spin_lock_bh(&master->lock.spinlock);
 216         master->lock.user_waiters--;
 217         spin_unlock_bh(&master->lock.spinlock);
 218         __set_current_state(TASK_RUNNING);
 219         remove_wait_queue(&master->lock.lock_queue, &entry);
 220
 221         DRM_DEBUG("%d %s\n", lock->context,
 222                   ret ? "interrupted" : "has lock");
 223         if (ret) return ret;
 224
 225         /* don't set the block all signals on the master process for now
 226          * really probably not the correct answer but lets us debug xkb
 227          * xserver for now */
 228         if (!drm_is_current_master(file_priv)) {
 229                 dev->sigdata.context = lock->context;
 230                 dev->sigdata.lock = master->lock.hw_lock;
 231         }
 232
 233         if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT))
 234         {
 235                 if (dev->driver->dma_quiescent(dev)) {
 236                         DRM_DEBUG("%d waiting for DMA quiescent\n",
 237                                   lock->context);
 238                         return -EBUSY;
 239                 }
 240         }
 241 #endif
 242
 243         return 0;
 244 }
 245
 246 /**
 247  * Unlock ioctl.
 248  *
 249  * \param inode device inode.
 250  * \param file_priv DRM file private.
 251  * \param cmd command.
 252  * \param arg user argument, pointing to a drm_lock structure.
 253  * \return zero on success or negative number on failure.
 254  *
 255  * Transfer and free the lock.
 256  */
 257 int drm_legacy_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv)
 258 {
 259 #if 0
 260         struct drm_lock *lock = data;
 261         struct drm_master *master = file_priv->master;
 262
 263         if (!drm_core_check_feature(dev, DRIVER_LEGACY))
 264                 return -EINVAL;
 265
 266         if (lock->context == DRM_KERNEL_CONTEXT) {
 267                 DRM_ERROR("Process %d using kernel context %d\n",
 268                           task_pid_nr(current), lock->context);
 269                 return -EINVAL;
 270         }
 271
 272         if (drm_legacy_lock_free(&master->lock, lock->context)) {
 273                 /* FIXME: Should really bail out here. */
 274         }
 275 #endif
 276
 277         return 0;
 278 }
 279
 280 #if 0
 281 /**
 282  * This function returns immediately and takes the hw lock
 283  * with the kernel context if it is free, otherwise it gets the highest priority when and if
 284  * it is eventually released.
 285  *
 286  * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held
 287  * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause
 288  * a deadlock, which is why the "idlelock" was invented).
 289  *
 290  * This should be sufficient to wait for GPU idle without
 291  * having to worry about starvation.
 292  */
 293
 294 void drm_legacy_idlelock_take(struct drm_lock_data *lock_data)
 295 {
 296         int ret;
 297
 298         spin_lock_bh(&lock_data->spinlock);
 299         lock_data->kernel_waiters++;
 300         if (!lock_data->idle_has_lock) {
 301
 302                 spin_unlock_bh(&lock_data->spinlock);
 303                 ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
 304                 spin_lock_bh(&lock_data->spinlock);
 305
 306                 if (ret == 1)
 307                         lock_data->idle_has_lock = 1;
 308         }
 309         spin_unlock_bh(&lock_data->spinlock);
 310 }
 311 EXPORT_SYMBOL(drm_legacy_idlelock_take);
 312
 313 void drm_legacy_idlelock_release(struct drm_lock_data *lock_data)
 314 {
 315         unsigned int old, prev;
 316         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 317
 318         spin_lock_bh(&lock_data->spinlock);
 319         if (--lock_data->kernel_waiters == 0) {
 320                 if (lock_data->idle_has_lock) {
 321                         do {
 322                                 old = *lock;
 323                                 prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT);
 324                         } while (prev != old);
 325                         wake_up_interruptible(&lock_data->lock_queue);
 326                         lock_data->idle_has_lock = 0;
 327                 }
 328         }
 329         spin_unlock_bh(&lock_data->spinlock);
 330 }
 331 EXPORT_SYMBOL(drm_legacy_idlelock_release);
 332
 333 static int drm_legacy_i_have_hw_lock(struct drm_device *dev,
 334                                      struct drm_file *file_priv)
 335 {
 336         struct drm_master *master = file_priv->master;
 337         return (file_priv->lock_count && master->lock.hw_lock &&
 338                 _DRM_LOCK_IS_HELD(master->lock.hw_lock->lock) &&
 339                 master->lock.file_priv == file_priv);
 340 }
 341 #endif
 342
 343 void drm_legacy_lock_release(struct drm_device *dev, struct file *filp)
 344 {
 345 #if 0
 346         struct drm_file *file_priv = filp->private_data;
 347
 348         /* if the master has gone away we can't do anything with the lock */
 349         if (!dev->master)
 350                 return;
 351
 352         if (drm_legacy_i_have_hw_lock(dev, file_priv)) {
 353                 DRM_DEBUG("File %p released, freeing lock for context %d\n",
 354                           filp, _DRM_LOCKING_CONTEXT(file_priv->master->lock.hw_lock->lock));
 355                 drm_legacy_lock_free(&file_priv->master->lock,
 356                                      _DRM_LOCKING_CONTEXT(file_priv->master->lock.hw_lock->lock));
 357         }
 358 #endif
 359 }