Merge branch 'locks' of git://linux-nfs.org/~bfields/linux
[linux-2.6] / 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_notifier(void *priv);
39
40 /**
41  * Lock ioctl.
42  *
43  * \param inode device inode.
44  * \param file_priv DRM file private.
45  * \param cmd command.
46  * \param arg user argument, pointing to a drm_lock structure.
47  * \return zero on success or negative number on failure.
48  *
49  * Add the current task to the lock wait queue, and attempt to take to lock.
50  */
51 int drm_lock(struct drm_device *dev, void *data, struct drm_file *file_priv)
52 {
53         DECLARE_WAITQUEUE(entry, current);
54         struct drm_lock *lock = data;
55         int ret = 0;
56
57         ++file_priv->lock_count;
58
59         if (lock->context == DRM_KERNEL_CONTEXT) {
60                 DRM_ERROR("Process %d using kernel context %d\n",
61                           current->pid, lock->context);
62                 return -EINVAL;
63         }
64
65         DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
66                   lock->context, current->pid,
67                   dev->lock.hw_lock->lock, lock->flags);
68
69         if (drm_core_check_feature(dev, DRIVER_DMA_QUEUE))
70                 if (lock->context < 0)
71                         return -EINVAL;
72
73         add_wait_queue(&dev->lock.lock_queue, &entry);
74         spin_lock(&dev->lock.spinlock);
75         dev->lock.user_waiters++;
76         spin_unlock(&dev->lock.spinlock);
77         for (;;) {
78                 __set_current_state(TASK_INTERRUPTIBLE);
79                 if (!dev->lock.hw_lock) {
80                         /* Device has been unregistered */
81                         ret = -EINTR;
82                         break;
83                 }
84                 if (drm_lock_take(&dev->lock, lock->context)) {
85                         dev->lock.file_priv = file_priv;
86                         dev->lock.lock_time = jiffies;
87                         atomic_inc(&dev->counts[_DRM_STAT_LOCKS]);
88                         break;  /* Got lock */
89                 }
90
91                 /* Contention */
92                 schedule();
93                 if (signal_pending(current)) {
94                         ret = -ERESTARTSYS;
95                         break;
96                 }
97         }
98         spin_lock(&dev->lock.spinlock);
99         dev->lock.user_waiters--;
100         spin_unlock(&dev->lock.spinlock);
101         __set_current_state(TASK_RUNNING);
102         remove_wait_queue(&dev->lock.lock_queue, &entry);
103
104         DRM_DEBUG("%d %s\n", lock->context,
105                   ret ? "interrupted" : "has lock");
106         if (ret) return ret;
107
108         sigemptyset(&dev->sigmask);
109         sigaddset(&dev->sigmask, SIGSTOP);
110         sigaddset(&dev->sigmask, SIGTSTP);
111         sigaddset(&dev->sigmask, SIGTTIN);
112         sigaddset(&dev->sigmask, SIGTTOU);
113         dev->sigdata.context = lock->context;
114         dev->sigdata.lock = dev->lock.hw_lock;
115         block_all_signals(drm_notifier, &dev->sigdata, &dev->sigmask);
116
117         if (dev->driver->dma_ready && (lock->flags & _DRM_LOCK_READY))
118                 dev->driver->dma_ready(dev);
119
120         if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT))
121         {
122                 if (dev->driver->dma_quiescent(dev)) {
123                         DRM_DEBUG("%d waiting for DMA quiescent\n",
124                                   lock->context);
125                         return -EBUSY;
126                 }
127         }
128
129         if (dev->driver->kernel_context_switch &&
130             dev->last_context != lock->context) {
131                 dev->driver->kernel_context_switch(dev, dev->last_context,
132                                                    lock->context);
133         }
134
135         return 0;
136 }
137
138 /**
139  * Unlock ioctl.
140  *
141  * \param inode device inode.
142  * \param file_priv DRM file private.
143  * \param cmd command.
144  * \param arg user argument, pointing to a drm_lock structure.
145  * \return zero on success or negative number on failure.
146  *
147  * Transfer and free the lock.
148  */
149 int drm_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv)
150 {
151         struct drm_lock *lock = data;
152         unsigned long irqflags;
153
154         if (lock->context == DRM_KERNEL_CONTEXT) {
155                 DRM_ERROR("Process %d using kernel context %d\n",
156                           current->pid, lock->context);
157                 return -EINVAL;
158         }
159
160         spin_lock_irqsave(&dev->tasklet_lock, irqflags);
161
162         if (dev->locked_tasklet_func) {
163                 dev->locked_tasklet_func(dev);
164
165                 dev->locked_tasklet_func = NULL;
166         }
167
168         spin_unlock_irqrestore(&dev->tasklet_lock, irqflags);
169
170         atomic_inc(&dev->counts[_DRM_STAT_UNLOCKS]);
171
172         /* kernel_context_switch isn't used by any of the x86 drm
173          * modules but is required by the Sparc driver.
174          */
175         if (dev->driver->kernel_context_switch_unlock)
176                 dev->driver->kernel_context_switch_unlock(dev);
177         else {
178                 if (drm_lock_free(&dev->lock,lock->context)) {
179                         /* FIXME: Should really bail out here. */
180                 }
181         }
182
183         unblock_all_signals();
184         return 0;
185 }
186
187 /**
188  * Take the heavyweight lock.
189  *
190  * \param lock lock pointer.
191  * \param context locking context.
192  * \return one if the lock is held, or zero otherwise.
193  *
194  * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
195  */
196 int drm_lock_take(struct drm_lock_data *lock_data,
197                   unsigned int context)
198 {
199         unsigned int old, new, prev;
200         volatile unsigned int *lock = &lock_data->hw_lock->lock;
201
202         spin_lock(&lock_data->spinlock);
203         do {
204                 old = *lock;
205                 if (old & _DRM_LOCK_HELD)
206                         new = old | _DRM_LOCK_CONT;
207                 else {
208                         new = context | _DRM_LOCK_HELD |
209                                 ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
210                                  _DRM_LOCK_CONT : 0);
211                 }
212                 prev = cmpxchg(lock, old, new);
213         } while (prev != old);
214         spin_unlock(&lock_data->spinlock);
215
216         if (_DRM_LOCKING_CONTEXT(old) == context) {
217                 if (old & _DRM_LOCK_HELD) {
218                         if (context != DRM_KERNEL_CONTEXT) {
219                                 DRM_ERROR("%d holds heavyweight lock\n",
220                                           context);
221                         }
222                         return 0;
223                 }
224         }
225
226         if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) {
227                 /* Have lock */
228                 return 1;
229         }
230         return 0;
231 }
232
233 /**
234  * This takes a lock forcibly and hands it to context.  Should ONLY be used
235  * inside *_unlock to give lock to kernel before calling *_dma_schedule.
236  *
237  * \param dev DRM device.
238  * \param lock lock pointer.
239  * \param context locking context.
240  * \return always one.
241  *
242  * Resets the lock file pointer.
243  * Marks the lock as held by the given context, via the \p cmpxchg instruction.
244  */
245 static int drm_lock_transfer(struct drm_lock_data *lock_data,
246                              unsigned int context)
247 {
248         unsigned int old, new, prev;
249         volatile unsigned int *lock = &lock_data->hw_lock->lock;
250
251         lock_data->file_priv = NULL;
252         do {
253                 old = *lock;
254                 new = context | _DRM_LOCK_HELD;
255                 prev = cmpxchg(lock, old, new);
256         } while (prev != old);
257         return 1;
258 }
259
260 /**
261  * Free lock.
262  *
263  * \param dev DRM device.
264  * \param lock lock.
265  * \param context context.
266  *
267  * Resets the lock file pointer.
268  * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
269  * waiting on the lock queue.
270  */
271 int drm_lock_free(struct drm_lock_data *lock_data, unsigned int context)
272 {
273         unsigned int old, new, prev;
274         volatile unsigned int *lock = &lock_data->hw_lock->lock;
275
276         spin_lock(&lock_data->spinlock);
277         if (lock_data->kernel_waiters != 0) {
278                 drm_lock_transfer(lock_data, 0);
279                 lock_data->idle_has_lock = 1;
280                 spin_unlock(&lock_data->spinlock);
281                 return 1;
282         }
283         spin_unlock(&lock_data->spinlock);
284
285         do {
286                 old = *lock;
287                 new = _DRM_LOCKING_CONTEXT(old);
288                 prev = cmpxchg(lock, old, new);
289         } while (prev != old);
290
291         if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
292                 DRM_ERROR("%d freed heavyweight lock held by %d\n",
293                           context, _DRM_LOCKING_CONTEXT(old));
294                 return 1;
295         }
296         wake_up_interruptible(&lock_data->lock_queue);
297         return 0;
298 }
299
300 /**
301  * If we get here, it means that the process has called DRM_IOCTL_LOCK
302  * without calling DRM_IOCTL_UNLOCK.
303  *
304  * If the lock is not held, then let the signal proceed as usual.  If the lock
305  * is held, then set the contended flag and keep the signal blocked.
306  *
307  * \param priv pointer to a drm_sigdata structure.
308  * \return one if the signal should be delivered normally, or zero if the
309  * signal should be blocked.
310  */
311 static int drm_notifier(void *priv)
312 {
313         struct drm_sigdata *s = (struct drm_sigdata *) priv;
314         unsigned int old, new, prev;
315
316         /* Allow signal delivery if lock isn't held */
317         if (!s->lock || !_DRM_LOCK_IS_HELD(s->lock->lock)
318             || _DRM_LOCKING_CONTEXT(s->lock->lock) != s->context)
319                 return 1;
320
321         /* Otherwise, set flag to force call to
322            drmUnlock */
323         do {
324                 old = s->lock->lock;
325                 new = old | _DRM_LOCK_CONT;
326                 prev = cmpxchg(&s->lock->lock, old, new);
327         } while (prev != old);
328         return 0;
329 }
330
331 /**
332  * This function returns immediately and takes the hw lock
333  * with the kernel context if it is free, otherwise it gets the highest priority when and if
334  * it is eventually released.
335  *
336  * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held
337  * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause
338  * a deadlock, which is why the "idlelock" was invented).
339  *
340  * This should be sufficient to wait for GPU idle without
341  * having to worry about starvation.
342  */
343
344 void drm_idlelock_take(struct drm_lock_data *lock_data)
345 {
346         int ret = 0;
347
348         spin_lock(&lock_data->spinlock);
349         lock_data->kernel_waiters++;
350         if (!lock_data->idle_has_lock) {
351
352                 spin_unlock(&lock_data->spinlock);
353                 ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
354                 spin_lock(&lock_data->spinlock);
355
356                 if (ret == 1)
357                         lock_data->idle_has_lock = 1;
358         }
359         spin_unlock(&lock_data->spinlock);
360 }
361 EXPORT_SYMBOL(drm_idlelock_take);
362
363 void drm_idlelock_release(struct drm_lock_data *lock_data)
364 {
365         unsigned int old, prev;
366         volatile unsigned int *lock = &lock_data->hw_lock->lock;
367
368         spin_lock(&lock_data->spinlock);
369         if (--lock_data->kernel_waiters == 0) {
370                 if (lock_data->idle_has_lock) {
371                         do {
372                                 old = *lock;
373                                 prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT);
374                         } while (prev != old);
375                         wake_up_interruptible(&lock_data->lock_queue);
376                         lock_data->idle_has_lock = 0;
377                 }
378         }
379         spin_unlock(&lock_data->spinlock);
380 }
381 EXPORT_SYMBOL(drm_idlelock_release);
382
383
384 int drm_i_have_hw_lock(struct drm_device *dev, struct drm_file *file_priv)
385 {
386         return (file_priv->lock_count && dev->lock.hw_lock &&
387                 _DRM_LOCK_IS_HELD(dev->lock.hw_lock->lock) &&
388                 dev->lock.file_priv == file_priv);
389 }
390
391 EXPORT_SYMBOL(drm_i_have_hw_lock);