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