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  * 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_legacy_lock(struct drm_device *dev, void *data,
  55                     struct drm_file *file_priv)
  56 {
  57         DECLARE_WAITQUEUE(entry, current);
  58         struct drm_lock *lock = data;
  59         struct drm_master *master = file_priv->master;
  60         int ret = 0;
  61
  62         if (drm_core_check_feature(dev, DRIVER_MODESET))
  63                 return -EINVAL;
  64
  65         ++file_priv->lock_count;
  66
  67         if (lock->context == DRM_KERNEL_CONTEXT) {
  68                 DRM_ERROR("Process %d using kernel context %d\n",
  69                           task_pid_nr(current), lock->context);
  70                 return -EINVAL;
  71         }
  72
  73         DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
  74                   lock->context, task_pid_nr(current),
  75                   master->lock.hw_lock->lock, lock->flags);
  76
  77         add_wait_queue(&master->lock.lock_queue, &entry);
  78         spin_lock_bh(&master->lock.spinlock);
  79         master->lock.user_waiters++;
  80         spin_unlock_bh(&master->lock.spinlock);
  81
  82         for (;;) {
  83                 __set_current_state(TASK_INTERRUPTIBLE);
  84                 if (!master->lock.hw_lock) {
  85                         /* Device has been unregistered */
  86                         send_sig(SIGTERM, current, 0);
  87                         ret = -EINTR;
  88                         break;
  89                 }
  90                 if (drm_lock_take(&master->lock, lock->context)) {
  91                         master->lock.file_priv = file_priv;
  92                         master->lock.lock_time = jiffies;
  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                 dev->sigdata.context = lock->context;
 120                 dev->sigdata.lock = master->lock.hw_lock;
 121         }
 122
 123         if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT))
 124         {
 125                 if (dev->driver->dma_quiescent(dev)) {
 126                         DRM_DEBUG("%d waiting for DMA quiescent\n",
 127                                   lock->context);
 128                         return -EBUSY;
 129                 }
 130         }
 131
 132         return 0;
 133 }
 134
 135 /**
 136  * Unlock ioctl.
 137  *
 138  * \param inode device inode.
 139  * \param file_priv DRM file private.
 140  * \param cmd command.
 141  * \param arg user argument, pointing to a drm_lock structure.
 142  * \return zero on success or negative number on failure.
 143  *
 144  * Transfer and free the lock.
 145  */
 146 int drm_legacy_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv)
 147 {
 148         struct drm_lock *lock = data;
 149         struct drm_master *master = file_priv->master;
 150
 151         if (drm_core_check_feature(dev, DRIVER_MODESET))
 152                 return -EINVAL;
 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         if (drm_legacy_lock_free(&master->lock, lock->context)) {
 161                 /* FIXME: Should really bail out here. */
 162         }
 163
 164         return 0;
 165 }
 166
 167 /**
 168  * Take the heavyweight lock.
 169  *
 170  * \param lock lock pointer.
 171  * \param context locking context.
 172  * \return one if the lock is held, or zero otherwise.
 173  *
 174  * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
 175  */
 176 static
 177 int drm_lock_take(struct drm_lock_data *lock_data,
 178                   unsigned int context)
 179 {
 180         unsigned int old, new, prev;
 181         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 182
 183         spin_lock_bh(&lock_data->spinlock);
 184         do {
 185                 old = *lock;
 186                 if (old & _DRM_LOCK_HELD)
 187                         new = old | _DRM_LOCK_CONT;
 188                 else {
 189                         new = context | _DRM_LOCK_HELD |
 190                                 ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
 191                                  _DRM_LOCK_CONT : 0);
 192                 }
 193                 prev = cmpxchg(lock, old, new);
 194         } while (prev != old);
 195         spin_unlock_bh(&lock_data->spinlock);
 196
 197         if (_DRM_LOCKING_CONTEXT(old) == context) {
 198                 if (old & _DRM_LOCK_HELD) {
 199                         if (context != DRM_KERNEL_CONTEXT) {
 200                                 DRM_ERROR("%d holds heavyweight lock\n",
 201                                           context);
 202                         }
 203                         return 0;
 204                 }
 205         }
 206
 207         if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) {
 208                 /* Have lock */
 209                 return 1;
 210         }
 211         return 0;
 212 }
 213
 214 /**
 215  * This takes a lock forcibly and hands it to context.  Should ONLY be used
 216  * inside *_unlock to give lock to kernel before calling *_dma_schedule.
 217  *
 218  * \param dev DRM device.
 219  * \param lock lock pointer.
 220  * \param context locking context.
 221  * \return always one.
 222  *
 223  * Resets the lock file pointer.
 224  * Marks the lock as held by the given context, via the \p cmpxchg instruction.
 225  */
 226 static int drm_lock_transfer(struct drm_lock_data *lock_data,
 227                              unsigned int context)
 228 {
 229         unsigned int old, new, prev;
 230         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 231
 232         lock_data->file_priv = NULL;
 233         do {
 234                 old = *lock;
 235                 new = context | _DRM_LOCK_HELD;
 236                 prev = cmpxchg(lock, old, new);
 237         } while (prev != old);
 238         return 1;
 239 }
 240
 241 /**
 242  * Free lock.
 243  *
 244  * \param dev DRM device.
 245  * \param lock lock.
 246  * \param context context.
 247  *
 248  * Resets the lock file pointer.
 249  * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
 250  * waiting on the lock queue.
 251  */
 252 int drm_legacy_lock_free(struct drm_lock_data *lock_data, unsigned int context)
 253 {
 254         unsigned int old, new, prev;
 255         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 256
 257         spin_lock_bh(&lock_data->spinlock);
 258         if (lock_data->kernel_waiters != 0) {
 259                 drm_lock_transfer(lock_data, 0);
 260                 lock_data->idle_has_lock = 1;
 261                 spin_unlock_bh(&lock_data->spinlock);
 262                 return 1;
 263         }
 264         spin_unlock_bh(&lock_data->spinlock);
 265
 266         do {
 267                 old = *lock;
 268                 new = _DRM_LOCKING_CONTEXT(old);
 269                 prev = cmpxchg(lock, old, new);
 270         } while (prev != old);
 271
 272         if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
 273                 DRM_ERROR("%d freed heavyweight lock held by %d\n",
 274                           context, _DRM_LOCKING_CONTEXT(old));
 275                 return 1;
 276         }
 277         wake_up_interruptible(&lock_data->lock_queue);
 278         return 0;
 279 }
 280
 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 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 }