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_notifier(void *priv);
  42
  43 static int drm_lock_take(struct drm_lock_data *lock_data, unsigned int context);
  44
  45 /**
  46  * Lock ioctl.
  47  *
  48  * \param inode device inode.
  49  * \param file_priv DRM file private.
  50  * \param cmd command.
  51  * \param arg user argument, pointing to a drm_lock structure.
  52  * \return zero on success or negative number on failure.
  53  *
  54  * Add the current task to the lock wait queue, and attempt to take to lock.
  55  */
  56 int drm_legacy_lock(struct drm_device *dev, void *data,
  57                     struct drm_file *file_priv)
  58 {
  59         DECLARE_WAITQUEUE(entry, current);
  60         struct drm_lock *lock = data;
  61         struct drm_master *master = file_priv->master;
  62         int ret = 0;
  63
  64         ++file_priv->lock_count;
  65
  66         if (lock->context == DRM_KERNEL_CONTEXT) {
  67                 DRM_ERROR("Process %d using kernel context %d\n",
  68                           task_pid_nr(current), lock->context);
  69                 return -EINVAL;
  70         }
  71
  72         DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
  73                   lock->context, task_pid_nr(current),
  74                   master->lock.hw_lock->lock, lock->flags);
  75
  76         add_wait_queue(&master->lock.lock_queue, &entry);
  77         spin_lock_bh(&master->lock.spinlock);
  78         master->lock.user_waiters++;
  79         spin_unlock_bh(&master->lock.spinlock);
  80
  81         for (;;) {
  82                 __set_current_state(TASK_INTERRUPTIBLE);
  83                 if (!master->lock.hw_lock) {
  84                         /* Device has been unregistered */
  85                         send_sig(SIGTERM, current, 0);
  86                         ret = -EINTR;
  87                         break;
  88                 }
  89                 if (drm_lock_take(&master->lock, lock->context)) {
  90                         master->lock.file_priv = file_priv;
  91                         master->lock.lock_time = jiffies;
  92                         break;  /* Got lock */
  93                 }
  94
  95                 /* Contention */
  96                 mutex_unlock(&drm_global_mutex);
  97                 schedule();
  98                 mutex_lock(&drm_global_mutex);
  99                 if (signal_pending(current)) {
 100                         ret = -EINTR;
 101                         break;
 102                 }
 103         }
 104         spin_lock_bh(&master->lock.spinlock);
 105         master->lock.user_waiters--;
 106         spin_unlock_bh(&master->lock.spinlock);
 107         __set_current_state(TASK_RUNNING);
 108         remove_wait_queue(&master->lock.lock_queue, &entry);
 109
 110         DRM_DEBUG("%d %s\n", lock->context,
 111                   ret ? "interrupted" : "has lock");
 112         if (ret) return ret;
 113
 114         /* don't set the block all signals on the master process for now
 115          * really probably not the correct answer but lets us debug xkb
 116          * xserver for now */
 117         if (!file_priv->is_master) {
 118                 sigemptyset(&dev->sigmask);
 119                 sigaddset(&dev->sigmask, SIGSTOP);
 120                 sigaddset(&dev->sigmask, SIGTSTP);
 121                 sigaddset(&dev->sigmask, SIGTTIN);
 122                 sigaddset(&dev->sigmask, SIGTTOU);
 123                 dev->sigdata.context = lock->context;
 124                 dev->sigdata.lock = master->lock.hw_lock;
 125                 block_all_signals(drm_notifier, dev, &dev->sigmask);
 126         }
 127
 128         if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT))
 129         {
 130                 if (dev->driver->dma_quiescent(dev)) {
 131                         DRM_DEBUG("%d waiting for DMA quiescent\n",
 132                                   lock->context);
 133                         return -EBUSY;
 134                 }
 135         }
 136
 137         return 0;
 138 }
 139
 140 /**
 141  * Unlock ioctl.
 142  *
 143  * \param inode device inode.
 144  * \param file_priv DRM file private.
 145  * \param cmd command.
 146  * \param arg user argument, pointing to a drm_lock structure.
 147  * \return zero on success or negative number on failure.
 148  *
 149  * Transfer and free the lock.
 150  */
 151 int drm_legacy_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv)
 152 {
 153         struct drm_lock *lock = data;
 154         struct drm_master *master = file_priv->master;
 155
 156         if (lock->context == DRM_KERNEL_CONTEXT) {
 157                 DRM_ERROR("Process %d using kernel context %d\n",
 158                           task_pid_nr(current), lock->context);
 159                 return -EINVAL;
 160         }
 161
 162         if (drm_legacy_lock_free(&master->lock, lock->context)) {
 163                 /* FIXME: Should really bail out here. */
 164         }
 165
 166         unblock_all_signals();
 167         return 0;
 168 }
 169
 170 /**
 171  * Take the heavyweight lock.
 172  *
 173  * \param lock lock pointer.
 174  * \param context locking context.
 175  * \return one if the lock is held, or zero otherwise.
 176  *
 177  * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
 178  */
 179 static
 180 int drm_lock_take(struct drm_lock_data *lock_data,
 181                   unsigned int context)
 182 {
 183         unsigned int old, new, prev;
 184         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 185
 186         spin_lock_bh(&lock_data->spinlock);
 187         do {
 188                 old = *lock;
 189                 if (old & _DRM_LOCK_HELD)
 190                         new = old | _DRM_LOCK_CONT;
 191                 else {
 192                         new = context | _DRM_LOCK_HELD |
 193                                 ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
 194                                  _DRM_LOCK_CONT : 0);
 195                 }
 196                 prev = cmpxchg(lock, old, new);
 197         } while (prev != old);
 198         spin_unlock_bh(&lock_data->spinlock);
 199
 200         if (_DRM_LOCKING_CONTEXT(old) == context) {
 201                 if (old & _DRM_LOCK_HELD) {
 202                         if (context != DRM_KERNEL_CONTEXT) {
 203                                 DRM_ERROR("%d holds heavyweight lock\n",
 204                                           context);
 205                         }
 206                         return 0;
 207                 }
 208         }
 209
 210         if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) {
 211                 /* Have lock */
 212                 return 1;
 213         }
 214         return 0;
 215 }
 216
 217 /**
 218  * This takes a lock forcibly and hands it to context.  Should ONLY be used
 219  * inside *_unlock to give lock to kernel before calling *_dma_schedule.
 220  *
 221  * \param dev DRM device.
 222  * \param lock lock pointer.
 223  * \param context locking context.
 224  * \return always one.
 225  *
 226  * Resets the lock file pointer.
 227  * Marks the lock as held by the given context, via the \p cmpxchg instruction.
 228  */
 229 static int drm_lock_transfer(struct drm_lock_data *lock_data,
 230                              unsigned int context)
 231 {
 232         unsigned int old, new, prev;
 233         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 234
 235         lock_data->file_priv = NULL;
 236         do {
 237                 old = *lock;
 238                 new = context | _DRM_LOCK_HELD;
 239                 prev = cmpxchg(lock, old, new);
 240         } while (prev != old);
 241         return 1;
 242 }
 243
 244 /**
 245  * Free lock.
 246  *
 247  * \param dev DRM device.
 248  * \param lock lock.
 249  * \param context context.
 250  *
 251  * Resets the lock file pointer.
 252  * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
 253  * waiting on the lock queue.
 254  */
 255 int drm_legacy_lock_free(struct drm_lock_data *lock_data, unsigned int context)
 256 {
 257         unsigned int old, new, prev;
 258         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 259
 260         spin_lock_bh(&lock_data->spinlock);
 261         if (lock_data->kernel_waiters != 0) {
 262                 drm_lock_transfer(lock_data, 0);
 263                 lock_data->idle_has_lock = 1;
 264                 spin_unlock_bh(&lock_data->spinlock);
 265                 return 1;
 266         }
 267         spin_unlock_bh(&lock_data->spinlock);
 268
 269         do {
 270                 old = *lock;
 271                 new = _DRM_LOCKING_CONTEXT(old);
 272                 prev = cmpxchg(lock, old, new);
 273         } while (prev != old);
 274
 275         if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
 276                 DRM_ERROR("%d freed heavyweight lock held by %d\n",
 277                           context, _DRM_LOCKING_CONTEXT(old));
 278                 return 1;
 279         }
 280         wake_up_interruptible(&lock_data->lock_queue);
 281         return 0;
 282 }
 283
 284 /**
 285  * If we get here, it means that the process has called DRM_IOCTL_LOCK
 286  * without calling DRM_IOCTL_UNLOCK.
 287  *
 288  * If the lock is not held, then let the signal proceed as usual.  If the lock
 289  * is held, then set the contended flag and keep the signal blocked.
 290  *
 291  * \param priv pointer to a drm_device structure.
 292  * \return one if the signal should be delivered normally, or zero if the
 293  * signal should be blocked.
 294  */
 295 static int drm_notifier(void *priv)
 296 {
 297         struct drm_device *dev = priv;
 298         struct drm_hw_lock *lock = dev->sigdata.lock;
 299         unsigned int old, new, prev;
 300
 301         /* Allow signal delivery if lock isn't held */
 302         if (!lock || !_DRM_LOCK_IS_HELD(lock->lock)
 303             || _DRM_LOCKING_CONTEXT(lock->lock) != dev->sigdata.context)
 304                 return 1;
 305
 306         /* Otherwise, set flag to force call to
 307            drmUnlock */
 308         do {
 309                 old = lock->lock;
 310                 new = old | _DRM_LOCK_CONT;
 311                 prev = cmpxchg(&lock->lock, old, new);
 312         } while (prev != old);
 313         return 0;
 314 }
 315
 316 /**
 317  * This function returns immediately and takes the hw lock
 318  * with the kernel context if it is free, otherwise it gets the highest priority when and if
 319  * it is eventually released.
 320  *
 321  * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held
 322  * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause
 323  * a deadlock, which is why the "idlelock" was invented).
 324  *
 325  * This should be sufficient to wait for GPU idle without
 326  * having to worry about starvation.
 327  */
 328
 329 void drm_legacy_idlelock_take(struct drm_lock_data *lock_data)
 330 {
 331         int ret;
 332
 333         spin_lock_bh(&lock_data->spinlock);
 334         lock_data->kernel_waiters++;
 335         if (!lock_data->idle_has_lock) {
 336
 337                 spin_unlock_bh(&lock_data->spinlock);
 338                 ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
 339                 spin_lock_bh(&lock_data->spinlock);
 340
 341                 if (ret == 1)
 342                         lock_data->idle_has_lock = 1;
 343         }
 344         spin_unlock_bh(&lock_data->spinlock);
 345 }
 346 EXPORT_SYMBOL(drm_legacy_idlelock_take);
 347
 348 void drm_legacy_idlelock_release(struct drm_lock_data *lock_data)
 349 {
 350         unsigned int old, prev;
 351         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 352
 353         spin_lock_bh(&lock_data->spinlock);
 354         if (--lock_data->kernel_waiters == 0) {
 355                 if (lock_data->idle_has_lock) {
 356                         do {
 357                                 old = *lock;
 358                                 prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT);
 359                         } while (prev != old);
 360                         wake_up_interruptible(&lock_data->lock_queue);
 361                         lock_data->idle_has_lock = 0;
 362                 }
 363         }
 364         spin_unlock_bh(&lock_data->spinlock);
 365 }
 366 EXPORT_SYMBOL(drm_legacy_idlelock_release);
 367
 368 int drm_legacy_i_have_hw_lock(struct drm_device *dev,
 369                               struct drm_file *file_priv)
 370 {
 371         struct drm_master *master = file_priv->master;
 372         return (file_priv->lock_count && master->lock.hw_lock &&
 373                 _DRM_LOCK_IS_HELD(master->lock.hw_lock->lock) &&
 374                 master->lock.file_priv == file_priv);
 375 }