Merge master.kernel.org:/pub/scm/linux/kernel/git/torvalds/linux-2.6 into for-linus
[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         unsigned long irqflags;
57
58         ++file_priv->lock_count;
59
60         if (lock->context == DRM_KERNEL_CONTEXT) {
61                 DRM_ERROR("Process %d using kernel context %d\n",
62                           task_pid_nr(current), lock->context);
63                 return -EINVAL;
64         }
65
66         DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
67                   lock->context, task_pid_nr(current),
68                   dev->lock.hw_lock->lock, lock->flags);
69
70         if (drm_core_check_feature(dev, DRIVER_DMA_QUEUE))
71                 if (lock->context < 0)
72                         return -EINVAL;
73
74         add_wait_queue(&dev->lock.lock_queue, &entry);
75         spin_lock_irqsave(&dev->lock.spinlock, irqflags);
76         dev->lock.user_waiters++;
77         spin_unlock_irqrestore(&dev->lock.spinlock, irqflags);
78         for (;;) {
79                 __set_current_state(TASK_INTERRUPTIBLE);
80                 if (!dev->lock.hw_lock) {
81                         /* Device has been unregistered */
82                         ret = -EINTR;
83                         break;
84                 }
85                 if (drm_lock_take(&dev->lock, lock->context)) {
86                         dev->lock.file_priv = file_priv;
87                         dev->lock.lock_time = jiffies;
88                         atomic_inc(&dev->counts[_DRM_STAT_LOCKS]);
89                         break;  /* Got lock */
90                 }
91
92                 /* Contention */
93                 schedule();
94                 if (signal_pending(current)) {
95                         ret = -ERESTARTSYS;
96                         break;
97                 }
98         }
99         spin_lock_irqsave(&dev->lock.spinlock, irqflags);
100         dev->lock.user_waiters--;
101         spin_unlock_irqrestore(&dev->lock.spinlock, irqflags);
102         __set_current_state(TASK_RUNNING);
103         remove_wait_queue(&dev->lock.lock_queue, &entry);
104
105         DRM_DEBUG("%d %s\n", lock->context,
106                   ret ? "interrupted" : "has lock");
107         if (ret) return ret;
108
109         sigemptyset(&dev->sigmask);
110         sigaddset(&dev->sigmask, SIGSTOP);
111         sigaddset(&dev->sigmask, SIGTSTP);
112         sigaddset(&dev->sigmask, SIGTTIN);
113         sigaddset(&dev->sigmask, SIGTTOU);
114         dev->sigdata.context = lock->context;
115         dev->sigdata.lock = dev->lock.hw_lock;
116         block_all_signals(drm_notifier, &dev->sigdata, &dev->sigmask);
117
118         if (dev->driver->dma_ready && (lock->flags & _DRM_LOCK_READY))
119                 dev->driver->dma_ready(dev);
120
121         if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT))
122         {
123                 if (dev->driver->dma_quiescent(dev)) {
124                         DRM_DEBUG("%d waiting for DMA quiescent\n",
125                                   lock->context);
126                         return -EBUSY;
127                 }
128         }
129
130         if (dev->driver->kernel_context_switch &&
131             dev->last_context != lock->context) {
132                 dev->driver->kernel_context_switch(dev, dev->last_context,
133                                                    lock->context);
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_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv)
151 {
152         struct drm_lock *lock = data;
153         unsigned long irqflags;
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         spin_lock_irqsave(&dev->tasklet_lock, irqflags);
162
163         if (dev->locked_tasklet_func) {
164                 dev->locked_tasklet_func(dev);
165
166                 dev->locked_tasklet_func = NULL;
167         }
168
169         spin_unlock_irqrestore(&dev->tasklet_lock, irqflags);
170
171         atomic_inc(&dev->counts[_DRM_STAT_UNLOCKS]);
172
173         /* kernel_context_switch isn't used by any of the x86 drm
174          * modules but is required by the Sparc driver.
175          */
176         if (dev->driver->kernel_context_switch_unlock)
177                 dev->driver->kernel_context_switch_unlock(dev);
178         else {
179                 if (drm_lock_free(&dev->lock,lock->context)) {
180                         /* FIXME: Should really bail out here. */
181                 }
182         }
183
184         unblock_all_signals();
185         return 0;
186 }
187
188 /**
189  * Take the heavyweight lock.
190  *
191  * \param lock lock pointer.
192  * \param context locking context.
193  * \return one if the lock is held, or zero otherwise.
194  *
195  * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
196  */
197 int drm_lock_take(struct drm_lock_data *lock_data,
198                   unsigned int context)
199 {
200         unsigned int old, new, prev;
201         volatile unsigned int *lock = &lock_data->hw_lock->lock;
202         unsigned long irqflags;
203
204         spin_lock_irqsave(&lock_data->spinlock, irqflags);
205         do {
206                 old = *lock;
207                 if (old & _DRM_LOCK_HELD)
208                         new = old | _DRM_LOCK_CONT;
209                 else {
210                         new = context | _DRM_LOCK_HELD |
211                                 ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
212                                  _DRM_LOCK_CONT : 0);
213                 }
214                 prev = cmpxchg(lock, old, new);
215         } while (prev != old);
216         spin_unlock_irqrestore(&lock_data->spinlock, irqflags);
217
218         if (_DRM_LOCKING_CONTEXT(old) == context) {
219                 if (old & _DRM_LOCK_HELD) {
220                         if (context != DRM_KERNEL_CONTEXT) {
221                                 DRM_ERROR("%d holds heavyweight lock\n",
222                                           context);
223                         }
224                         return 0;
225                 }
226         }
227
228         if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) {
229                 /* Have lock */
230                 return 1;
231         }
232         return 0;
233 }
234
235 /**
236  * This takes a lock forcibly and hands it to context.  Should ONLY be used
237  * inside *_unlock to give lock to kernel before calling *_dma_schedule.
238  *
239  * \param dev DRM device.
240  * \param lock lock pointer.
241  * \param context locking context.
242  * \return always one.
243  *
244  * Resets the lock file pointer.
245  * Marks the lock as held by the given context, via the \p cmpxchg instruction.
246  */
247 static int drm_lock_transfer(struct drm_lock_data *lock_data,
248                              unsigned int context)
249 {
250         unsigned int old, new, prev;
251         volatile unsigned int *lock = &lock_data->hw_lock->lock;
252
253         lock_data->file_priv = NULL;
254         do {
255                 old = *lock;
256                 new = context | _DRM_LOCK_HELD;
257                 prev = cmpxchg(lock, old, new);
258         } while (prev != old);
259         return 1;
260 }
261
262 /**
263  * Free lock.
264  *
265  * \param dev DRM device.
266  * \param lock lock.
267  * \param context context.
268  *
269  * Resets the lock file pointer.
270  * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
271  * waiting on the lock queue.
272  */
273 int drm_lock_free(struct drm_lock_data *lock_data, unsigned int context)
274 {
275         unsigned int old, new, prev;
276         volatile unsigned int *lock = &lock_data->hw_lock->lock;
277         unsigned long irqflags;
278
279         spin_lock_irqsave(&lock_data->spinlock, irqflags);
280         if (lock_data->kernel_waiters != 0) {
281                 drm_lock_transfer(lock_data, 0);
282                 lock_data->idle_has_lock = 1;
283                 spin_unlock_irqrestore(&lock_data->spinlock, irqflags);
284                 return 1;
285         }
286         spin_unlock_irqrestore(&lock_data->spinlock, irqflags);
287
288         do {
289                 old = *lock;
290                 new = _DRM_LOCKING_CONTEXT(old);
291                 prev = cmpxchg(lock, old, new);
292         } while (prev != old);
293
294         if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
295                 DRM_ERROR("%d freed heavyweight lock held by %d\n",
296                           context, _DRM_LOCKING_CONTEXT(old));
297                 return 1;
298         }
299         wake_up_interruptible(&lock_data->lock_queue);
300         return 0;
301 }
302
303 /**
304  * If we get here, it means that the process has called DRM_IOCTL_LOCK
305  * without calling DRM_IOCTL_UNLOCK.
306  *
307  * If the lock is not held, then let the signal proceed as usual.  If the lock
308  * is held, then set the contended flag and keep the signal blocked.
309  *
310  * \param priv pointer to a drm_sigdata structure.
311  * \return one if the signal should be delivered normally, or zero if the
312  * signal should be blocked.
313  */
314 static int drm_notifier(void *priv)
315 {
316         struct drm_sigdata *s = (struct drm_sigdata *) priv;
317         unsigned int old, new, prev;
318
319         /* Allow signal delivery if lock isn't held */
320         if (!s->lock || !_DRM_LOCK_IS_HELD(s->lock->lock)
321             || _DRM_LOCKING_CONTEXT(s->lock->lock) != s->context)
322                 return 1;
323
324         /* Otherwise, set flag to force call to
325            drmUnlock */
326         do {
327                 old = s->lock->lock;
328                 new = old | _DRM_LOCK_CONT;
329                 prev = cmpxchg(&s->lock->lock, old, new);
330         } while (prev != old);
331         return 0;
332 }
333
334 /**
335  * This function returns immediately and takes the hw lock
336  * with the kernel context if it is free, otherwise it gets the highest priority when and if
337  * it is eventually released.
338  *
339  * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held
340  * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause
341  * a deadlock, which is why the "idlelock" was invented).
342  *
343  * This should be sufficient to wait for GPU idle without
344  * having to worry about starvation.
345  */
346
347 void drm_idlelock_take(struct drm_lock_data *lock_data)
348 {
349         int ret = 0;
350         unsigned long irqflags;
351
352         spin_lock_irqsave(&lock_data->spinlock, irqflags);
353         lock_data->kernel_waiters++;
354         if (!lock_data->idle_has_lock) {
355
356                 spin_unlock_irqrestore(&lock_data->spinlock, irqflags);
357                 ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
358                 spin_lock_irqsave(&lock_data->spinlock, irqflags);
359
360                 if (ret == 1)
361                         lock_data->idle_has_lock = 1;
362         }
363         spin_unlock_irqrestore(&lock_data->spinlock, irqflags);
364 }
365 EXPORT_SYMBOL(drm_idlelock_take);
366
367 void drm_idlelock_release(struct drm_lock_data *lock_data)
368 {
369         unsigned int old, prev;
370         volatile unsigned int *lock = &lock_data->hw_lock->lock;
371         unsigned long irqflags;
372
373         spin_lock_irqsave(&lock_data->spinlock, irqflags);
374         if (--lock_data->kernel_waiters == 0) {
375                 if (lock_data->idle_has_lock) {
376                         do {
377                                 old = *lock;
378                                 prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT);
379                         } while (prev != old);
380                         wake_up_interruptible(&lock_data->lock_queue);
381                         lock_data->idle_has_lock = 0;
382                 }
383         }
384         spin_unlock_irqrestore(&lock_data->spinlock, irqflags);
385 }
386 EXPORT_SYMBOL(drm_idlelock_release);
387
388
389 int drm_i_have_hw_lock(struct drm_device *dev, struct drm_file *file_priv)
390 {
391         return (file_priv->lock_count && dev->lock.hw_lock &&
392                 _DRM_LOCK_IS_HELD(dev->lock.hw_lock->lock) &&
393                 dev->lock.file_priv == file_priv);
394 }
395
396 EXPORT_SYMBOL(drm_i_have_hw_lock);