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);
397
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