drm_lock.c revision 08f2e669a81b5906adf6e4716f92d99d7966d224 
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
38static 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 */
51int 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	struct drm_master *master = file_priv->master;
56	int ret = 0;
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		  master->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(&master->lock.lock_queue, &entry);
75	spin_lock_bh(&master->lock.spinlock);
76	master->lock.user_waiters++;
77	spin_unlock_bh(&master->lock.spinlock);
78
79	for (;;) {
80		__set_current_state(TASK_INTERRUPTIBLE);
81		if (!master->lock.hw_lock) {
82			/* Device has been unregistered */
83			send_sig(SIGTERM, current, 0);
84			ret = -EINTR;
85			break;
86		}
87		if (drm_lock_take(&master->lock, lock->context)) {
88			master->lock.file_priv = file_priv;
89			master->lock.lock_time = jiffies;
90			atomic_inc(&dev->counts[_DRM_STAT_LOCKS]);
91			break;	/* Got lock */
92		}
93
94		/* Contention */
95		mutex_unlock(&drm_global_mutex);
96		schedule();
97		mutex_lock(&drm_global_mutex);
98		if (signal_pending(current)) {
99			ret = -EINTR;
100			break;
101		}
102	}
103	spin_lock_bh(&master->lock.spinlock);
104	master->lock.user_waiters--;
105	spin_unlock_bh(&master->lock.spinlock);
106	__set_current_state(TASK_RUNNING);
107	remove_wait_queue(&master->lock.lock_queue, &entry);
108
109	DRM_DEBUG("%d %s\n", lock->context,
110		  ret ? "interrupted" : "has lock");
111	if (ret) return ret;
112
113	/* don't set the block all signals on the master process for now
114	 * really probably not the correct answer but lets us debug xkb
115 	 * xserver for now */
116	if (!file_priv->is_master) {
117		sigemptyset(&dev->sigmask);
118		sigaddset(&dev->sigmask, SIGSTOP);
119		sigaddset(&dev->sigmask, SIGTSTP);
120		sigaddset(&dev->sigmask, SIGTTIN);
121		sigaddset(&dev->sigmask, SIGTTOU);
122		dev->sigdata.context = lock->context;
123		dev->sigdata.lock = master->lock.hw_lock;
124		block_all_signals(drm_notifier, &dev->sigdata, &dev->sigmask);
125	}
126
127	if (dev->driver->dma_ready && (lock->flags & _DRM_LOCK_READY))
128		dev->driver->dma_ready(dev);
129
130	if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT))
131	{
132		if (dev->driver->dma_quiescent(dev)) {
133			DRM_DEBUG("%d waiting for DMA quiescent\n",
134				  lock->context);
135			return -EBUSY;
136		}
137	}
138
139	if (dev->driver->kernel_context_switch &&
140	    dev->last_context != lock->context) {
141		dev->driver->kernel_context_switch(dev, dev->last_context,
142						   lock->context);
143	}
144
145	return 0;
146}
147
148/**
149 * Unlock ioctl.
150 *
151 * \param inode device inode.
152 * \param file_priv DRM file private.
153 * \param cmd command.
154 * \param arg user argument, pointing to a drm_lock structure.
155 * \return zero on success or negative number on failure.
156 *
157 * Transfer and free the lock.
158 */
159int drm_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv)
160{
161	struct drm_lock *lock = data;
162	struct drm_master *master = file_priv->master;
163
164	if (lock->context == DRM_KERNEL_CONTEXT) {
165		DRM_ERROR("Process %d using kernel context %d\n",
166			  task_pid_nr(current), lock->context);
167		return -EINVAL;
168	}
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(&master->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 */
196int 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_bh(&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_bh(&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}
232EXPORT_SYMBOL(drm_lock_take);
233
234/**
235 * This takes a lock forcibly and hands it to context.	Should ONLY be used
236 * inside *_unlock to give lock to kernel before calling *_dma_schedule.
237 *
238 * \param dev DRM device.
239 * \param lock lock pointer.
240 * \param context locking context.
241 * \return always one.
242 *
243 * Resets the lock file pointer.
244 * Marks the lock as held by the given context, via the \p cmpxchg instruction.
245 */
246static int drm_lock_transfer(struct drm_lock_data *lock_data,
247			     unsigned int context)
248{
249	unsigned int old, new, prev;
250	volatile unsigned int *lock = &lock_data->hw_lock->lock;
251
252	lock_data->file_priv = NULL;
253	do {
254		old = *lock;
255		new = context | _DRM_LOCK_HELD;
256		prev = cmpxchg(lock, old, new);
257	} while (prev != old);
258	return 1;
259}
260
261/**
262 * Free lock.
263 *
264 * \param dev DRM device.
265 * \param lock lock.
266 * \param context context.
267 *
268 * Resets the lock file pointer.
269 * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
270 * waiting on the lock queue.
271 */
272int drm_lock_free(struct drm_lock_data *lock_data, unsigned int context)
273{
274	unsigned int old, new, prev;
275	volatile unsigned int *lock = &lock_data->hw_lock->lock;
276
277	spin_lock_bh(&lock_data->spinlock);
278	if (lock_data->kernel_waiters != 0) {
279		drm_lock_transfer(lock_data, 0);
280		lock_data->idle_has_lock = 1;
281		spin_unlock_bh(&lock_data->spinlock);
282		return 1;
283	}
284	spin_unlock_bh(&lock_data->spinlock);
285
286	do {
287		old = *lock;
288		new = _DRM_LOCKING_CONTEXT(old);
289		prev = cmpxchg(lock, old, new);
290	} while (prev != old);
291
292	if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
293		DRM_ERROR("%d freed heavyweight lock held by %d\n",
294			  context, _DRM_LOCKING_CONTEXT(old));
295		return 1;
296	}
297	wake_up_interruptible(&lock_data->lock_queue);
298	return 0;
299}
300EXPORT_SYMBOL(drm_lock_free);
301
302/**
303 * If we get here, it means that the process has called DRM_IOCTL_LOCK
304 * without calling DRM_IOCTL_UNLOCK.
305 *
306 * If the lock is not held, then let the signal proceed as usual.  If the lock
307 * is held, then set the contended flag and keep the signal blocked.
308 *
309 * \param priv pointer to a drm_sigdata structure.
310 * \return one if the signal should be delivered normally, or zero if the
311 * signal should be blocked.
312 */
313static int drm_notifier(void *priv)
314{
315	struct drm_sigdata *s = (struct drm_sigdata *) priv;
316	unsigned int old, new, prev;
317
318	/* Allow signal delivery if lock isn't held */
319	if (!s->lock || !_DRM_LOCK_IS_HELD(s->lock->lock)
320	    || _DRM_LOCKING_CONTEXT(s->lock->lock) != s->context)
321		return 1;
322
323	/* Otherwise, set flag to force call to
324	   drmUnlock */
325	do {
326		old = s->lock->lock;
327		new = old | _DRM_LOCK_CONT;
328		prev = cmpxchg(&s->lock->lock, old, new);
329	} while (prev != old);
330	return 0;
331}
332
333/**
334 * This function returns immediately and takes the hw lock
335 * with the kernel context if it is free, otherwise it gets the highest priority when and if
336 * it is eventually released.
337 *
338 * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held
339 * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause
340 * a deadlock, which is why the "idlelock" was invented).
341 *
342 * This should be sufficient to wait for GPU idle without
343 * having to worry about starvation.
344 */
345
346void drm_idlelock_take(struct drm_lock_data *lock_data)
347{
348	int ret = 0;
349
350	spin_lock_bh(&lock_data->spinlock);
351	lock_data->kernel_waiters++;
352	if (!lock_data->idle_has_lock) {
353
354		spin_unlock_bh(&lock_data->spinlock);
355		ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
356		spin_lock_bh(&lock_data->spinlock);
357
358		if (ret == 1)
359			lock_data->idle_has_lock = 1;
360	}
361	spin_unlock_bh(&lock_data->spinlock);
362}
363EXPORT_SYMBOL(drm_idlelock_take);
364
365void drm_idlelock_release(struct drm_lock_data *lock_data)
366{
367	unsigned int old, prev;
368	volatile unsigned int *lock = &lock_data->hw_lock->lock;
369
370	spin_lock_bh(&lock_data->spinlock);
371	if (--lock_data->kernel_waiters == 0) {
372		if (lock_data->idle_has_lock) {
373			do {
374				old = *lock;
375				prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT);
376			} while (prev != old);
377			wake_up_interruptible(&lock_data->lock_queue);
378			lock_data->idle_has_lock = 0;
379		}
380	}
381	spin_unlock_bh(&lock_data->spinlock);
382}
383EXPORT_SYMBOL(drm_idlelock_release);
384
385
386int drm_i_have_hw_lock(struct drm_device *dev, struct drm_file *file_priv)
387{
388	struct drm_master *master = file_priv->master;
389	return (file_priv->lock_count && master->lock.hw_lock &&
390		_DRM_LOCK_IS_HELD(master->lock.hw_lock->lock) &&
391		master->lock.file_priv == file_priv);
392}
393
394EXPORT_SYMBOL(drm_i_have_hw_lock);
395