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 "drmP.h"
  38
  39 static int drm_notifier(void *priv);
  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_lock(struct drm_device *dev, void *data, struct drm_file *file_priv)
  55 {
  56         DECLARE_WAITQUEUE(entry, current);
  57         struct drm_lock *lock = data;
  58         struct drm_master *master = file_priv->master;
  59         int ret = 0;
  60
  61         ++file_priv->lock_count;
  62
  63         if (lock->context == DRM_KERNEL_CONTEXT) {
  64                 DRM_ERROR("Process %d using kernel context %d\n",
  65                           task_pid_nr(current), lock->context);
  66                 return -EINVAL;
  67         }
  68
  69         DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
  70                   lock->context, task_pid_nr(current),
  71                   master->lock.hw_lock->lock, lock->flags);
  72
  73         if (drm_core_check_feature(dev, DRIVER_DMA_QUEUE))
  74                 if (lock->context < 0)
  75                         return -EINVAL;
  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                         atomic_inc(&dev->counts[_DRM_STAT_LOCKS]);
  94                         break;  /* Got lock */
  95                 }
  96
  97                 /* Contention */
  98                 mutex_unlock(&drm_global_mutex);
  99                 schedule();
 100                 mutex_lock(&drm_global_mutex);
 101                 if (signal_pending(current)) {
 102                         ret = -EINTR;
 103                         break;
 104                 }
 105         }
 106         spin_lock_bh(&master->lock.spinlock);
 107         master->lock.user_waiters--;
 108         spin_unlock_bh(&master->lock.spinlock);
 109         __set_current_state(TASK_RUNNING);
 110         remove_wait_queue(&master->lock.lock_queue, &entry);
 111
 112         DRM_DEBUG("%d %s\n", lock->context,
 113                   ret ? "interrupted" : "has lock");
 114         if (ret) return ret;
 115
 116         /* don't set the block all signals on the master process for now
 117          * really probably not the correct answer but lets us debug xkb
 118          * xserver for now */
 119         if (!file_priv->is_master) {
 120                 sigemptyset(&dev->sigmask);
 121                 sigaddset(&dev->sigmask, SIGSTOP);
 122                 sigaddset(&dev->sigmask, SIGTSTP);
 123                 sigaddset(&dev->sigmask, SIGTTIN);
 124                 sigaddset(&dev->sigmask, SIGTTOU);
 125                 dev->sigdata.context = lock->context;
 126                 dev->sigdata.lock = master->lock.hw_lock;
 127                 block_all_signals(drm_notifier, &dev->sigdata, &dev->sigmask);
 128         }
 129
 130         if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT))
 131         {
 132                 if (dev->driver->dma_quiescent(dev)) {
 133                         DRM_DEBUG("%d waiting for DMA quiescent\n",
 134                                   lock->context);
 135                         return -EBUSY;
 136                 }
 137         }
 138
 139         return 0;
 140 }
 141
 142 /**
 143  * Unlock ioctl.
 144  *
 145  * \param inode device inode.
 146  * \param file_priv DRM file private.
 147  * \param cmd command.
 148  * \param arg user argument, pointing to a drm_lock structure.
 149  * \return zero on success or negative number on failure.
 150  *
 151  * Transfer and free the lock.
 152  */
 153 int drm_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv)
 154 {
 155         struct drm_lock *lock = data;
 156         struct drm_master *master = file_priv->master;
 157
 158         if (lock->context == DRM_KERNEL_CONTEXT) {
 159                 DRM_ERROR("Process %d using kernel context %d\n",
 160                           task_pid_nr(current), lock->context);
 161                 return -EINVAL;
 162         }
 163
 164         atomic_inc(&dev->counts[_DRM_STAT_UNLOCKS]);
 165
 166         if (drm_lock_free(&master->lock, lock->context)) {
 167                 /* FIXME: Should really bail out here. */
 168         }
 169
 170         unblock_all_signals();
 171         return 0;
 172 }
 173
 174 /**
 175  * Take the heavyweight lock.
 176  *
 177  * \param lock lock pointer.
 178  * \param context locking context.
 179  * \return one if the lock is held, or zero otherwise.
 180  *
 181  * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
 182  */
 183 static
 184 int drm_lock_take(struct drm_lock_data *lock_data,
 185                   unsigned int context)
 186 {
 187         unsigned int old, new, prev;
 188         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 189
 190         spin_lock_bh(&lock_data->spinlock);
 191         do {
 192                 old = *lock;
 193                 if (old & _DRM_LOCK_HELD)
 194                         new = old | _DRM_LOCK_CONT;
 195                 else {
 196                         new = context | _DRM_LOCK_HELD |
 197                                 ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
 198                                  _DRM_LOCK_CONT : 0);
 199                 }
 200                 prev = cmpxchg(lock, old, new);
 201         } while (prev != old);
 202         spin_unlock_bh(&lock_data->spinlock);
 203
 204         if (_DRM_LOCKING_CONTEXT(old) == context) {
 205                 if (old & _DRM_LOCK_HELD) {
 206                         if (context != DRM_KERNEL_CONTEXT) {
 207                                 DRM_ERROR("%d holds heavyweight lock\n",
 208                                           context);
 209                         }
 210                         return 0;
 211                 }
 212         }
 213
 214         if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) {
 215                 /* Have lock */
 216                 return 1;
 217         }
 218         return 0;
 219 }
 220
 221 /**
 222  * This takes a lock forcibly and hands it to context.  Should ONLY be used
 223  * inside *_unlock to give lock to kernel before calling *_dma_schedule.
 224  *
 225  * \param dev DRM device.
 226  * \param lock lock pointer.
 227  * \param context locking context.
 228  * \return always one.
 229  *
 230  * Resets the lock file pointer.
 231  * Marks the lock as held by the given context, via the \p cmpxchg instruction.
 232  */
 233 static int drm_lock_transfer(struct drm_lock_data *lock_data,
 234                              unsigned int context)
 235 {
 236         unsigned int old, new, prev;
 237         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 238
 239         lock_data->file_priv = NULL;
 240         do {
 241                 old = *lock;
 242                 new = context | _DRM_LOCK_HELD;
 243                 prev = cmpxchg(lock, old, new);
 244         } while (prev != old);
 245         return 1;
 246 }
 247
 248 /**
 249  * Free lock.
 250  *
 251  * \param dev DRM device.
 252  * \param lock lock.
 253  * \param context context.
 254  *
 255  * Resets the lock file pointer.
 256  * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
 257  * waiting on the lock queue.
 258  */
 259 int drm_lock_free(struct drm_lock_data *lock_data, unsigned int context)
 260 {
 261         unsigned int old, new, prev;
 262         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 263
 264         spin_lock_bh(&lock_data->spinlock);
 265         if (lock_data->kernel_waiters != 0) {
 266                 drm_lock_transfer(lock_data, 0);
 267                 lock_data->idle_has_lock = 1;
 268                 spin_unlock_bh(&lock_data->spinlock);
 269                 return 1;
 270         }
 271         spin_unlock_bh(&lock_data->spinlock);
 272
 273         do {
 274                 old = *lock;
 275                 new = _DRM_LOCKING_CONTEXT(old);
 276                 prev = cmpxchg(lock, old, new);
 277         } while (prev != old);
 278
 279         if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
 280                 DRM_ERROR("%d freed heavyweight lock held by %d\n",
 281                           context, _DRM_LOCKING_CONTEXT(old));
 282                 return 1;
 283         }
 284         wake_up_interruptible(&lock_data->lock_queue);
 285         return 0;
 286 }
 287
 288 /**
 289  * If we get here, it means that the process has called DRM_IOCTL_LOCK
 290  * without calling DRM_IOCTL_UNLOCK.
 291  *
 292  * If the lock is not held, then let the signal proceed as usual.  If the lock
 293  * is held, then set the contended flag and keep the signal blocked.
 294  *
 295  * \param priv pointer to a drm_sigdata structure.
 296  * \return one if the signal should be delivered normally, or zero if the
 297  * signal should be blocked.
 298  */
 299 static int drm_notifier(void *priv)
 300 {
 301         struct drm_sigdata *s = (struct drm_sigdata *) priv;
 302         unsigned int old, new, prev;
 303
 304         /* Allow signal delivery if lock isn't held */
 305         if (!s->lock || !_DRM_LOCK_IS_HELD(s->lock->lock)
 306             || _DRM_LOCKING_CONTEXT(s->lock->lock) != s->context)
 307                 return 1;
 308
 309         /* Otherwise, set flag to force call to
 310            drmUnlock */
 311         do {
 312                 old = s->lock->lock;
 313                 new = old | _DRM_LOCK_CONT;
 314                 prev = cmpxchg(&s->lock->lock, old, new);
 315         } while (prev != old);
 316         return 0;
 317 }
 318
 319 /**
 320  * This function returns immediately and takes the hw lock
 321  * with the kernel context if it is free, otherwise it gets the highest priority when and if
 322  * it is eventually released.
 323  *
 324  * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held
 325  * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause
 326  * a deadlock, which is why the "idlelock" was invented).
 327  *
 328  * This should be sufficient to wait for GPU idle without
 329  * having to worry about starvation.
 330  */
 331
 332 void drm_idlelock_take(struct drm_lock_data *lock_data)
 333 {
 334         int ret;
 335
 336         spin_lock_bh(&lock_data->spinlock);
 337         lock_data->kernel_waiters++;
 338         if (!lock_data->idle_has_lock) {
 339
 340                 spin_unlock_bh(&lock_data->spinlock);
 341                 ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
 342                 spin_lock_bh(&lock_data->spinlock);
 343
 344                 if (ret == 1)
 345                         lock_data->idle_has_lock = 1;
 346         }
 347         spin_unlock_bh(&lock_data->spinlock);
 348 }
 349 EXPORT_SYMBOL(drm_idlelock_take);
 350
 351 void drm_idlelock_release(struct drm_lock_data *lock_data)
 352 {
 353         unsigned int old, prev;
 354         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 355
 356         spin_lock_bh(&lock_data->spinlock);
 357         if (--lock_data->kernel_waiters == 0) {
 358                 if (lock_data->idle_has_lock) {
 359                         do {
 360                                 old = *lock;
 361                                 prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT);
 362                         } while (prev != old);
 363                         wake_up_interruptible(&lock_data->lock_queue);
 364                         lock_data->idle_has_lock = 0;
 365                 }
 366         }
 367         spin_unlock_bh(&lock_data->spinlock);
 368 }
 369 EXPORT_SYMBOL(drm_idlelock_release);
 370
 371 int drm_i_have_hw_lock(struct drm_device *dev, struct drm_file *file_priv)
 372 {
 373         struct drm_master *master = file_priv->master;
 374         return (file_priv->lock_count && master->lock.hw_lock &&
 375                 _DRM_LOCK_IS_HELD(master->lock.hw_lock->lock) &&
 376                 master->lock.file_priv == file_priv);
 377 }