drivers/char/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 "drmP.h"
  37
  38 static int drm_lock_transfer(drm_device_t * dev,
  39                              __volatile__ unsigned int *lock,
  40                              unsigned int context);
  41 static int drm_notifier(void *priv);
  42
  43 /**
  44  * Lock ioctl.
  45  *
  46  * \param inode device inode.
  47  * \param filp file pointer.
  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 inode *inode, struct file *filp,
  55              unsigned int cmd, unsigned long arg)
  56 {
  57         drm_file_t *priv = filp->private_data;
  58         drm_device_t *dev = priv->head->dev;
  59         DECLARE_WAITQUEUE(entry, current);
  60         drm_lock_t lock;
  61         int ret = 0;
  62
  63         ++priv->lock_count;
  64
  65         if (copy_from_user(&lock, (drm_lock_t __user *) arg, sizeof(lock)))
  66                 return -EFAULT;
  67
  68         if (lock.context == DRM_KERNEL_CONTEXT) {
  69                 DRM_ERROR("Process %d using kernel context %d\n",
  70                           current->pid, lock.context);
  71                 return -EINVAL;
  72         }
  73
  74         DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
  75                   lock.context, current->pid,
  76                   dev->lock.hw_lock->lock, lock.flags);
  77
  78         if (drm_core_check_feature(dev, DRIVER_DMA_QUEUE))
  79                 if (lock.context < 0)
  80                         return -EINVAL;
  81
  82         add_wait_queue(&dev->lock.lock_queue, &entry);
  83         for (;;) {
  84                 __set_current_state(TASK_INTERRUPTIBLE);
  85                 if (!dev->lock.hw_lock) {
  86                         /* Device has been unregistered */
  87                         ret = -EINTR;
  88                         break;
  89                 }
  90                 if (drm_lock_take(&dev->lock.hw_lock->lock, lock.context)) {
  91                         dev->lock.filp = filp;
  92                         dev->lock.lock_time = jiffies;
  93                         atomic_inc(&dev->counts[_DRM_STAT_LOCKS]);
  94                         break;  /* Got lock */
  95                 }
  96
  97                 /* Contention */
  98                 schedule();
  99                 if (signal_pending(current)) {
 100                         ret = -ERESTARTSYS;
 101                         break;
 102                 }
 103         }
 104         __set_current_state(TASK_RUNNING);
 105         remove_wait_queue(&dev->lock.lock_queue, &entry);
 106
 107         sigemptyset(&dev->sigmask);
 108         sigaddset(&dev->sigmask, SIGSTOP);
 109         sigaddset(&dev->sigmask, SIGTSTP);
 110         sigaddset(&dev->sigmask, SIGTTIN);
 111         sigaddset(&dev->sigmask, SIGTTOU);
 112         dev->sigdata.context = lock.context;
 113         dev->sigdata.lock = dev->lock.hw_lock;
 114         block_all_signals(drm_notifier, &dev->sigdata, &dev->sigmask);
 115
 116         if (dev->driver->dma_ready && (lock.flags & _DRM_LOCK_READY))
 117                 dev->driver->dma_ready(dev);
 118
 119         if (dev->driver->dma_quiescent && (lock.flags & _DRM_LOCK_QUIESCENT))
 120                 return dev->driver->dma_quiescent(dev);
 121
 122         /* dev->driver->kernel_context_switch isn't used by any of the x86
 123          *  drivers but is used by the Sparc driver.
 124          */
 125
 126         if (dev->driver->kernel_context_switch &&
 127             dev->last_context != lock.context) {
 128                 dev->driver->kernel_context_switch(dev, dev->last_context,
 129                                                    lock.context);
 130         }
 131         DRM_DEBUG("%d %s\n", lock.context, ret ? "interrupted" : "has lock");
 132
 133         return ret;
 134 }
 135
 136 /**
 137  * Unlock ioctl.
 138  *
 139  * \param inode device inode.
 140  * \param filp file pointer.
 141  * \param cmd command.
 142  * \param arg user argument, pointing to a drm_lock structure.
 143  * \return zero on success or negative number on failure.
 144  *
 145  * Transfer and free the lock.
 146  */
 147 int drm_unlock(struct inode *inode, struct file *filp,
 148                unsigned int cmd, unsigned long arg)
 149 {
 150         drm_file_t *priv = filp->private_data;
 151         drm_device_t *dev = priv->head->dev;
 152         drm_lock_t lock;
 153
 154         if (copy_from_user(&lock, (drm_lock_t __user *) arg, sizeof(lock)))
 155                 return -EFAULT;
 156
 157         if (lock.context == DRM_KERNEL_CONTEXT) {
 158                 DRM_ERROR("Process %d using kernel context %d\n",
 159                           current->pid, lock.context);
 160                 return -EINVAL;
 161         }
 162
 163         atomic_inc(&dev->counts[_DRM_STAT_UNLOCKS]);
 164
 165         /* kernel_context_switch isn't used by any of the x86 drm
 166          * modules but is required by the Sparc driver.
 167          */
 168         if (dev->driver->kernel_context_switch_unlock)
 169                 dev->driver->kernel_context_switch_unlock(dev, &lock);
 170         else {
 171                 drm_lock_transfer(dev, &dev->lock.hw_lock->lock,
 172                                   DRM_KERNEL_CONTEXT);
 173
 174                 if (drm_lock_free(dev, &dev->lock.hw_lock->lock,
 175                                   DRM_KERNEL_CONTEXT)) {
 176                         DRM_ERROR("\n");
 177                 }
 178         }
 179
 180         unblock_all_signals();
 181         return 0;
 182 }
 183
 184 /**
 185  * Take the heavyweight lock.
 186  *
 187  * \param lock lock pointer.
 188  * \param context locking context.
 189  * \return one if the lock is held, or zero otherwise.
 190  *
 191  * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
 192  */
 193 int drm_lock_take(__volatile__ unsigned int *lock, unsigned int context)
 194 {
 195         unsigned int old, new, prev;
 196
 197         do {
 198                 old = *lock;
 199                 if (old & _DRM_LOCK_HELD)
 200                         new = old | _DRM_LOCK_CONT;
 201                 else
 202                         new = context | _DRM_LOCK_HELD;
 203                 prev = cmpxchg(lock, old, new);
 204         } while (prev != old);
 205         if (_DRM_LOCKING_CONTEXT(old) == context) {
 206                 if (old & _DRM_LOCK_HELD) {
 207                         if (context != DRM_KERNEL_CONTEXT) {
 208                                 DRM_ERROR("%d holds heavyweight lock\n",
 209                                           context);
 210                         }
 211                         return 0;
 212                 }
 213         }
 214         if (new == (context | _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(drm_device_t * dev,
 234                              __volatile__ unsigned int *lock,
 235                              unsigned int context)
 236 {
 237         unsigned int old, new, prev;
 238
 239         dev->lock.filp = 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(drm_device_t * dev,
 260                   __volatile__ unsigned int *lock, unsigned int context)
 261 {
 262         unsigned int old, new, prev;
 263
 264         dev->lock.filp = NULL;
 265         do {
 266                 old = *lock;
 267                 new = 0;
 268                 prev = cmpxchg(lock, old, new);
 269         } while (prev != old);
 270         if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
 271                 DRM_ERROR("%d freed heavyweight lock held by %d\n",
 272                           context, _DRM_LOCKING_CONTEXT(old));
 273                 return 1;
 274         }
 275         wake_up_interruptible(&dev->lock.lock_queue);
 276         return 0;
 277 }
 278
 279 /**
 280  * If we get here, it means that the process has called DRM_IOCTL_LOCK
 281  * without calling DRM_IOCTL_UNLOCK.
 282  *
 283  * If the lock is not held, then let the signal proceed as usual.  If the lock
 284  * is held, then set the contended flag and keep the signal blocked.
 285  *
 286  * \param priv pointer to a drm_sigdata structure.
 287  * \return one if the signal should be delivered normally, or zero if the
 288  * signal should be blocked.
 289  */
 290 static int drm_notifier(void *priv)
 291 {
 292         drm_sigdata_t *s = (drm_sigdata_t *) priv;
 293         unsigned int old, new, prev;
 294
 295         /* Allow signal delivery if lock isn't held */
 296         if (!s->lock || !_DRM_LOCK_IS_HELD(s->lock->lock)
 297             || _DRM_LOCKING_CONTEXT(s->lock->lock) != s->context)
 298                 return 1;
 299
 300         /* Otherwise, set flag to force call to
 301            drmUnlock */
 302         do {
 303                 old = s->lock->lock;
 304                 new = old | _DRM_LOCK_CONT;
 305                 prev = cmpxchg(&s->lock->lock, old, new);
 306         } while (prev != old);
 307         return 0;
 308 }