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