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
  40 static int drm_notifier(void *priv);
  41
  42 static int drm_lock_take(struct drm_lock_data *lock_data, unsigned int context);
  43
  44 /**
  45  * Lock ioctl.
  46  *
  47  * \param inode device inode.
  48  * \param file_priv DRM file private.
  49  * \param cmd command.
  50  * \param arg user argument, pointing to a drm_lock structure.
  51  * \return zero on success or negative number on failure.
  52  *
  53  * Add the current task to the lock wait queue, and attempt to take to lock.
  54  */
  55 int drm_legacy_lock(struct drm_device *dev, void *data,
  56                     struct drm_file *file_priv)
  57 {
  58         DECLARE_WAITQUEUE(entry, current);
  59         struct drm_lock *lock = data;
  60         struct drm_master *master = file_priv->master;
  61         int ret = 0;
  62
  63         ++file_priv->lock_count;
  64
  65         if (lock->context == DRM_KERNEL_CONTEXT) {
  66                 DRM_ERROR("Process %d using kernel context %d\n",
  67                           task_pid_nr(current), lock->context);
  68                 return -EINVAL;
  69         }
  70
  71         DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
  72                   lock->context, task_pid_nr(current),
  73                   master->lock.hw_lock->lock, lock->flags);
  74
  75         add_wait_queue(&master->lock.lock_queue, &entry);
  76         spin_lock_bh(&master->lock.spinlock);
  77         master->lock.user_waiters++;
  78         spin_unlock_bh(&master->lock.spinlock);
  79
  80         for (;;) {
  81                 __set_current_state(TASK_INTERRUPTIBLE);
  82                 if (!master->lock.hw_lock) {
  83                         /* Device has been unregistered */
  84                         send_sig(SIGTERM, current, 0);
  85                         ret = -EINTR;
  86                         break;
  87                 }
  88                 if (drm_lock_take(&master->lock, lock->context)) {
  89                         master->lock.file_priv = file_priv;
  90                         master->lock.lock_time = jiffies;
  91                         break;  /* Got lock */
  92                 }
  93
  94                 /* Contention */
  95                 mutex_unlock(&drm_global_mutex);
  96                 schedule();
  97                 mutex_lock(&drm_global_mutex);
  98                 if (signal_pending(current)) {
  99                         ret = -EINTR;
 100                         break;
 101                 }
 102         }
 103         spin_lock_bh(&master->lock.spinlock);
 104         master->lock.user_waiters--;
 105         spin_unlock_bh(&master->lock.spinlock);
 106         __set_current_state(TASK_RUNNING);
 107         remove_wait_queue(&master->lock.lock_queue, &entry);
 108
 109         DRM_DEBUG("%d %s\n", lock->context,
 110                   ret ? "interrupted" : "has lock");
 111         if (ret) return ret;
 112
 113         /* don't set the block all signals on the master process for now
 114          * really probably not the correct answer but lets us debug xkb
 115          * xserver for now */
 116         if (!file_priv->is_master) {
 117                 sigemptyset(&dev->sigmask);
 118                 sigaddset(&dev->sigmask, SIGSTOP);
 119                 sigaddset(&dev->sigmask, SIGTSTP);
 120                 sigaddset(&dev->sigmask, SIGTTIN);
 121                 sigaddset(&dev->sigmask, SIGTTOU);
 122                 dev->sigdata.context = lock->context;
 123                 dev->sigdata.lock = master->lock.hw_lock;
 124                 block_all_signals(drm_notifier, dev, &dev->sigmask);
 125         }
 126
 127         if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT))
 128         {
 129                 if (dev->driver->dma_quiescent(dev)) {
 130                         DRM_DEBUG("%d waiting for DMA quiescent\n",
 131                                   lock->context);
 132                         return -EBUSY;
 133                 }
 134         }
 135
 136         return 0;
 137 }
 138
 139 /**
 140  * Unlock ioctl.
 141  *
 142  * \param inode device inode.
 143  * \param file_priv DRM file private.
 144  * \param cmd command.
 145  * \param arg user argument, pointing to a drm_lock structure.
 146  * \return zero on success or negative number on failure.
 147  *
 148  * Transfer and free the lock.
 149  */
 150 int drm_legacy_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv)
 151 {
 152         struct drm_lock *lock = data;
 153         struct drm_master *master = file_priv->master;
 154
 155         if (lock->context == DRM_KERNEL_CONTEXT) {
 156                 DRM_ERROR("Process %d using kernel context %d\n",
 157                           task_pid_nr(current), lock->context);
 158                 return -EINVAL;
 159         }
 160
 161         if (drm_legacy_lock_free(&master->lock, lock->context)) {
 162                 /* FIXME: Should really bail out here. */
 163         }
 164
 165         unblock_all_signals();
 166         return 0;
 167 }
 168
 169 /**
 170  * Take the heavyweight lock.
 171  *
 172  * \param lock lock pointer.
 173  * \param context locking context.
 174  * \return one if the lock is held, or zero otherwise.
 175  *
 176  * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
 177  */
 178 static
 179 int drm_lock_take(struct drm_lock_data *lock_data,
 180                   unsigned int context)
 181 {
 182         unsigned int old, new, prev;
 183         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 184
 185         spin_lock_bh(&lock_data->spinlock);
 186         do {
 187                 old = *lock;
 188                 if (old & _DRM_LOCK_HELD)
 189                         new = old | _DRM_LOCK_CONT;
 190                 else {
 191                         new = context | _DRM_LOCK_HELD |
 192                                 ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
 193                                  _DRM_LOCK_CONT : 0);
 194                 }
 195                 prev = cmpxchg(lock, old, new);
 196         } while (prev != old);
 197         spin_unlock_bh(&lock_data->spinlock);
 198
 199         if (_DRM_LOCKING_CONTEXT(old) == context) {
 200                 if (old & _DRM_LOCK_HELD) {
 201                         if (context != DRM_KERNEL_CONTEXT) {
 202                                 DRM_ERROR("%d holds heavyweight lock\n",
 203                                           context);
 204                         }
 205                         return 0;
 206                 }
 207         }
 208
 209         if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) {
 210                 /* Have lock */
 211                 return 1;
 212         }
 213         return 0;
 214 }
 215
 216 /**
 217  * This takes a lock forcibly and hands it to context.  Should ONLY be used
 218  * inside *_unlock to give lock to kernel before calling *_dma_schedule.
 219  *
 220  * \param dev DRM device.
 221  * \param lock lock pointer.
 222  * \param context locking context.
 223  * \return always one.
 224  *
 225  * Resets the lock file pointer.
 226  * Marks the lock as held by the given context, via the \p cmpxchg instruction.
 227  */
 228 static int drm_lock_transfer(struct drm_lock_data *lock_data,
 229                              unsigned int context)
 230 {
 231         unsigned int old, new, prev;
 232         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 233
 234         lock_data->file_priv = NULL;
 235         do {
 236                 old = *lock;
 237                 new = context | _DRM_LOCK_HELD;
 238                 prev = cmpxchg(lock, old, new);
 239         } while (prev != old);
 240         return 1;
 241 }
 242
 243 /**
 244  * Free lock.
 245  *
 246  * \param dev DRM device.
 247  * \param lock lock.
 248  * \param context context.
 249  *
 250  * Resets the lock file pointer.
 251  * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
 252  * waiting on the lock queue.
 253  */
 254 int drm_legacy_lock_free(struct drm_lock_data *lock_data, unsigned int context)
 255 {
 256         unsigned int old, new, prev;
 257         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 258
 259         spin_lock_bh(&lock_data->spinlock);
 260         if (lock_data->kernel_waiters != 0) {
 261                 drm_lock_transfer(lock_data, 0);
 262                 lock_data->idle_has_lock = 1;
 263                 spin_unlock_bh(&lock_data->spinlock);
 264                 return 1;
 265         }
 266         spin_unlock_bh(&lock_data->spinlock);
 267
 268         do {
 269                 old = *lock;
 270                 new = _DRM_LOCKING_CONTEXT(old);
 271                 prev = cmpxchg(lock, old, new);
 272         } while (prev != old);
 273
 274         if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
 275                 DRM_ERROR("%d freed heavyweight lock held by %d\n",
 276                           context, _DRM_LOCKING_CONTEXT(old));
 277                 return 1;
 278         }
 279         wake_up_interruptible(&lock_data->lock_queue);
 280         return 0;
 281 }
 282
 283 /**
 284  * If we get here, it means that the process has called DRM_IOCTL_LOCK
 285  * without calling DRM_IOCTL_UNLOCK.
 286  *
 287  * If the lock is not held, then let the signal proceed as usual.  If the lock
 288  * is held, then set the contended flag and keep the signal blocked.
 289  *
 290  * \param priv pointer to a drm_device structure.
 291  * \return one if the signal should be delivered normally, or zero if the
 292  * signal should be blocked.
 293  */
 294 static int drm_notifier(void *priv)
 295 {
 296         struct drm_device *dev = priv;
 297         struct drm_hw_lock *lock = dev->sigdata.lock;
 298         unsigned int old, new, prev;
 299
 300         /* Allow signal delivery if lock isn't held */
 301         if (!lock || !_DRM_LOCK_IS_HELD(lock->lock)
 302             || _DRM_LOCKING_CONTEXT(lock->lock) != dev->sigdata.context)
 303                 return 1;
 304
 305         /* Otherwise, set flag to force call to
 306            drmUnlock */
 307         do {
 308                 old = lock->lock;
 309                 new = old | _DRM_LOCK_CONT;
 310                 prev = cmpxchg(&lock->lock, old, new);
 311         } while (prev != old);
 312         return 0;
 313 }
 314
 315 /**
 316  * This function returns immediately and takes the hw lock
 317  * with the kernel context if it is free, otherwise it gets the highest priority when and if
 318  * it is eventually released.
 319  *
 320  * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held
 321  * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause
 322  * a deadlock, which is why the "idlelock" was invented).
 323  *
 324  * This should be sufficient to wait for GPU idle without
 325  * having to worry about starvation.
 326  */
 327
 328 void drm_legacy_idlelock_take(struct drm_lock_data *lock_data)
 329 {
 330         int ret;
 331
 332         spin_lock_bh(&lock_data->spinlock);
 333         lock_data->kernel_waiters++;
 334         if (!lock_data->idle_has_lock) {
 335
 336                 spin_unlock_bh(&lock_data->spinlock);
 337                 ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
 338                 spin_lock_bh(&lock_data->spinlock);
 339
 340                 if (ret == 1)
 341                         lock_data->idle_has_lock = 1;
 342         }
 343         spin_unlock_bh(&lock_data->spinlock);
 344 }
 345 EXPORT_SYMBOL(drm_legacy_idlelock_take);
 346
 347 void drm_legacy_idlelock_release(struct drm_lock_data *lock_data)
 348 {
 349         unsigned int old, prev;
 350         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 351
 352         spin_lock_bh(&lock_data->spinlock);
 353         if (--lock_data->kernel_waiters == 0) {
 354                 if (lock_data->idle_has_lock) {
 355                         do {
 356                                 old = *lock;
 357                                 prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT);
 358                         } while (prev != old);
 359                         wake_up_interruptible(&lock_data->lock_queue);
 360                         lock_data->idle_has_lock = 0;
 361                 }
 362         }
 363         spin_unlock_bh(&lock_data->spinlock);
 364 }
 365 EXPORT_SYMBOL(drm_legacy_idlelock_release);
 366
 367 int drm_legacy_i_have_hw_lock(struct drm_device *dev,
 368                               struct drm_file *file_priv)
 369 {
 370         struct drm_master *master = file_priv->master;
 371         return (file_priv->lock_count && master->lock.hw_lock &&
 372                 _DRM_LOCK_IS_HELD(master->lock.hw_lock->lock) &&
 373                 master->lock.file_priv == file_priv);
 374 }