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 filp file pointer.
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 inode *inode, struct file *filp,
52	     unsigned int cmd, unsigned long arg)
53{
54	drm_file_t *priv = filp->private_data;
55	drm_device_t *dev = priv->head->dev;
56	DECLARE_WAITQUEUE(entry, current);
57	drm_lock_t lock;
58	int ret = 0;
59
60	++priv->lock_count;
61
62	if (copy_from_user(&lock, (drm_lock_t __user *) arg, sizeof(lock)))
63		return -EFAULT;
64
65	if (lock.context == DRM_KERNEL_CONTEXT) {
66		DRM_ERROR("Process %d using kernel context %d\n",
67			  current->pid, lock.context);
68		return -EINVAL;
69	}
70
71	DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
72		  lock.context, current->pid,
73		  dev->lock.hw_lock->lock, lock.flags);
74
75	if (drm_core_check_feature(dev, DRIVER_DMA_QUEUE))
76		if (lock.context < 0)
77			return -EINVAL;
78
79	add_wait_queue(&dev->lock.lock_queue, &entry);
80	spin_lock(&dev->lock.spinlock);
81	dev->lock.user_waiters++;
82	spin_unlock(&dev->lock.spinlock);
83	for (;;) {
84		__set_current_state(TASK_INTERRUPTIBLE);
85		if (!dev->lock.hw_lock) {
86			/* Device has been unregistered */
87			ret = -EINTR;
88			break;
89		}
90		if (drm_lock_take(&dev->lock, lock.context)) {
91			dev->lock.filp = filp;
92			dev->lock.lock_time = jiffies;
93			atomic_inc(&dev->counts[_DRM_STAT_LOCKS]);
94			break;	/* Got lock */
95		}
96
97		/* Contention */
98		schedule();
99		if (signal_pending(current)) {
100			ret = -ERESTARTSYS;
101			break;
102		}
103	}
104	spin_lock(&dev->lock.spinlock);
105	dev->lock.user_waiters--;
106	spin_unlock(&dev->lock.spinlock);
107	__set_current_state(TASK_RUNNING);
108	remove_wait_queue(&dev->lock.lock_queue, &entry);
109
110	DRM_DEBUG( "%d %s\n", lock.context, ret ? "interrupted" : "has lock" );
111	if (ret) return ret;
112
113	sigemptyset(&dev->sigmask);
114	sigaddset(&dev->sigmask, SIGSTOP);
115	sigaddset(&dev->sigmask, SIGTSTP);
116	sigaddset(&dev->sigmask, SIGTTIN);
117	sigaddset(&dev->sigmask, SIGTTOU);
118	dev->sigdata.context = lock.context;
119	dev->sigdata.lock = dev->lock.hw_lock;
120	block_all_signals(drm_notifier, &dev->sigdata, &dev->sigmask);
121
122	if (dev->driver->dma_ready && (lock.flags & _DRM_LOCK_READY))
123		dev->driver->dma_ready(dev);
124
125	if (dev->driver->dma_quiescent && (lock.flags & _DRM_LOCK_QUIESCENT)) {
126		if (dev->driver->dma_quiescent(dev)) {
127			DRM_DEBUG("%d waiting for DMA quiescent\n", lock.context);
128			return DRM_ERR(EBUSY);
129		}
130	}
131
132	if (dev->driver->kernel_context_switch &&
133	    dev->last_context != lock.context) {
134		dev->driver->kernel_context_switch(dev, dev->last_context,
135						   lock.context);
136	}
137
138	return 0;
139}
140
141/**
142 * Unlock ioctl.
143 *
144 * \param inode device inode.
145 * \param filp file pointer.
146 * \param cmd command.
147 * \param arg user argument, pointing to a drm_lock structure.
148 * \return zero on success or negative number on failure.
149 *
150 * Transfer and free the lock.
151 */
152int drm_unlock(struct inode *inode, struct file *filp,
153	       unsigned int cmd, unsigned long arg)
154{
155	drm_file_t *priv = filp->private_data;
156	drm_device_t *dev = priv->head->dev;
157	drm_lock_t lock;
158	unsigned long irqflags;
159
160	if (copy_from_user(&lock, (drm_lock_t __user *) arg, sizeof(lock)))
161		return -EFAULT;
162
163	if (lock.context == DRM_KERNEL_CONTEXT) {
164		DRM_ERROR("Process %d using kernel context %d\n",
165			  current->pid, lock.context);
166		return -EINVAL;
167	}
168
169	spin_lock_irqsave(&dev->tasklet_lock, irqflags);
170
171	if (dev->locked_tasklet_func) {
172		dev->locked_tasklet_func(dev);
173
174		dev->locked_tasklet_func = NULL;
175	}
176
177	spin_unlock_irqrestore(&dev->tasklet_lock, irqflags);
178
179	atomic_inc(&dev->counts[_DRM_STAT_UNLOCKS]);
180
181	/* kernel_context_switch isn't used by any of the x86 drm
182	 * modules but is required by the Sparc driver.
183	 */
184	if (dev->driver->kernel_context_switch_unlock)
185		dev->driver->kernel_context_switch_unlock(dev);
186	else {
187		if (drm_lock_free(&dev->lock,lock.context)) {
188		}
189	}
190
191	unblock_all_signals();
192	return 0;
193}
194
195/**
196 * Take the heavyweight lock.
197 *
198 * \param lock lock pointer.
199 * \param context locking context.
200 * \return one if the lock is held, or zero otherwise.
201 *
202 * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
203 */
204int drm_lock_take(drm_lock_data_t *lock_data,
205		  unsigned int context)
206{
207	unsigned int old, new, prev;
208	volatile unsigned int *lock = &lock_data->hw_lock->lock;
209
210	spin_lock(&lock_data->spinlock);
211	do {
212		old = *lock;
213		if (old & _DRM_LOCK_HELD)
214			new = old | _DRM_LOCK_CONT;
215		else {
216			new = context | _DRM_LOCK_HELD |
217				((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
218				 _DRM_LOCK_CONT : 0);
219		}
220		prev = cmpxchg(lock, old, new);
221	} while (prev != old);
222	spin_unlock(&lock_data->spinlock);
223
224	if (_DRM_LOCKING_CONTEXT(old) == context) {
225		if (old & _DRM_LOCK_HELD) {
226			if (context != DRM_KERNEL_CONTEXT) {
227				DRM_ERROR("%d holds heavyweight lock\n",
228					  context);
229			}
230			return 0;
231		}
232	}
233
234	if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) {
235		/* Have lock */
236		return 1;
237	}
238	return 0;
239}
240
241/**
242 * This takes a lock forcibly and hands it to context.	Should ONLY be used
243 * inside *_unlock to give lock to kernel before calling *_dma_schedule.
244 *
245 * \param dev DRM device.
246 * \param lock lock pointer.
247 * \param context locking context.
248 * \return always one.
249 *
250 * Resets the lock file pointer.
251 * Marks the lock as held by the given context, via the \p cmpxchg instruction.
252 */
253static int drm_lock_transfer(drm_lock_data_t *lock_data,
254			     unsigned int context)
255{
256	unsigned int old, new, prev;
257	volatile unsigned int *lock = &lock_data->hw_lock->lock;
258
259	lock_data->filp = NULL;
260	do {
261		old = *lock;
262		new = context | _DRM_LOCK_HELD;
263		prev = cmpxchg(lock, old, new);
264	} while (prev != old);
265	return 1;
266}
267
268/**
269 * Free lock.
270 *
271 * \param dev DRM device.
272 * \param lock lock.
273 * \param context context.
274 *
275 * Resets the lock file pointer.
276 * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
277 * waiting on the lock queue.
278 */
279int drm_lock_free(drm_lock_data_t *lock_data, unsigned int context)
280{
281	unsigned int old, new, prev;
282	volatile unsigned int *lock = &lock_data->hw_lock->lock;
283
284	spin_lock(&lock_data->spinlock);
285	if (lock_data->kernel_waiters != 0) {
286		drm_lock_transfer(lock_data, 0);
287		lock_data->idle_has_lock = 1;
288		spin_unlock(&lock_data->spinlock);
289		return 1;
290	}
291	spin_unlock(&lock_data->spinlock);
292
293	do {
294		old = *lock;
295		new = _DRM_LOCKING_CONTEXT(old);
296		prev = cmpxchg(lock, old, new);
297	} while (prev != old);
298
299	if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
300		DRM_ERROR("%d freed heavyweight lock held by %d\n",
301			  context, _DRM_LOCKING_CONTEXT(old));
302		return 1;
303	}
304	wake_up_interruptible(&lock_data->lock_queue);
305	return 0;
306}
307
308/**
309 * If we get here, it means that the process has called DRM_IOCTL_LOCK
310 * without calling DRM_IOCTL_UNLOCK.
311 *
312 * If the lock is not held, then let the signal proceed as usual.  If the lock
313 * is held, then set the contended flag and keep the signal blocked.
314 *
315 * \param priv pointer to a drm_sigdata structure.
316 * \return one if the signal should be delivered normally, or zero if the
317 * signal should be blocked.
318 */
319static int drm_notifier(void *priv)
320{
321	drm_sigdata_t *s = (drm_sigdata_t *) priv;
322	unsigned int old, new, prev;
323
324	/* Allow signal delivery if lock isn't held */
325	if (!s->lock || !_DRM_LOCK_IS_HELD(s->lock->lock)
326	    || _DRM_LOCKING_CONTEXT(s->lock->lock) != s->context)
327		return 1;
328
329	/* Otherwise, set flag to force call to
330	   drmUnlock */
331	do {
332		old = s->lock->lock;
333		new = old | _DRM_LOCK_CONT;
334		prev = cmpxchg(&s->lock->lock, old, new);
335	} while (prev != old);
336	return 0;
337}
338
339/**
340 * This function returns immediately and takes the hw lock
341 * with the kernel context if it is free, otherwise it gets the highest priority when and if
342 * it is eventually released.
343 *
344 * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held
345 * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause
346 * a deadlock, which is why the "idlelock" was invented).
347 *
348 * This should be sufficient to wait for GPU idle without
349 * having to worry about starvation.
350 */
351
352void drm_idlelock_take(drm_lock_data_t *lock_data)
353{
354	int ret = 0;
355
356	spin_lock(&lock_data->spinlock);
357	lock_data->kernel_waiters++;
358	if (!lock_data->idle_has_lock) {
359
360		spin_unlock(&lock_data->spinlock);
361		ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
362		spin_lock(&lock_data->spinlock);
363
364		if (ret == 1)
365			lock_data->idle_has_lock = 1;
366	}
367	spin_unlock(&lock_data->spinlock);
368}
369EXPORT_SYMBOL(drm_idlelock_take);
370
371void drm_idlelock_release(drm_lock_data_t *lock_data)
372{
373	unsigned int old, prev;
374	volatile unsigned int *lock = &lock_data->hw_lock->lock;
375
376	spin_lock(&lock_data->spinlock);
377	if (--lock_data->kernel_waiters == 0) {
378		if (lock_data->idle_has_lock) {
379			do {
380				old = *lock;
381				prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT);
382			} while (prev != old);
383			wake_up_interruptible(&lock_data->lock_queue);
384			lock_data->idle_has_lock = 0;
385		}
386	}
387	spin_unlock(&lock_data->spinlock);
388}
389EXPORT_SYMBOL(drm_idlelock_release);
390
391
392int drm_i_have_hw_lock(struct file *filp)
393{
394	DRM_DEVICE;
395
396	return (priv->lock_count && dev->lock.hw_lock &&
397		_DRM_LOCK_IS_HELD(dev->lock.hw_lock->lock) &&
398		dev->lock.filp == filp);
399}
400
401EXPORT_SYMBOL(drm_i_have_hw_lock);
402