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 <sys/cdefs.h>
37__FBSDID("$FreeBSD: stable/10/sys/dev/drm2/drm_lock.c 314593 2017-03-03 12:03:50Z avg $");
38
39#include <dev/drm2/drmP.h>
40
41#if defined(__linux__)
42static int drm_notifier(void *priv);
43#endif
44
45static int drm_lock_take(struct drm_lock_data *lock_data, unsigned int context);
46
47/**
48 * Lock ioctl.
49 *
50 * \param inode device inode.
51 * \param file_priv DRM file private.
52 * \param cmd command.
53 * \param arg user argument, pointing to a drm_lock structure.
54 * \return zero on success or negative number on failure.
55 *
56 * Add the current task to the lock wait queue, and attempt to take to lock.
57 */
58int drm_lock(struct drm_device *dev, void *data, struct drm_file *file_priv)
59{
60	struct drm_lock *lock = data;
61	struct drm_master *master = file_priv->master;
62	int ret = 0;
63
64	++file_priv->lock_count;
65
66	if (lock->context == DRM_KERNEL_CONTEXT) {
67		DRM_ERROR("Process %d using kernel context %d\n",
68			  DRM_CURRENTPID, lock->context);
69		return -EINVAL;
70	}
71
72	DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
73		  lock->context, DRM_CURRENTPID,
74		  master->lock.hw_lock->lock, lock->flags);
75
76	mtx_lock(&master->lock.spinlock);
77	master->lock.user_waiters++;
78	mtx_unlock(&master->lock.spinlock);
79
80	for (;;) {
81#if defined(__linux__)
82		if (!master->lock.hw_lock) {
83			/* Device has been unregistered */
84			send_sig(SIGTERM, current, 0);
85			ret = -EINTR;
86			break;
87		}
88#endif
89		if (drm_lock_take(&master->lock, lock->context)) {
90			master->lock.file_priv = file_priv;
91			master->lock.lock_time = jiffies;
92			atomic_inc(&dev->counts[_DRM_STAT_LOCKS]);
93			break;	/* Got lock */
94		}
95
96		/* Contention */
97		DRM_UNLOCK_ASSERT(dev);
98		ret = -sx_sleep(&master->lock.lock_queue, &drm_global_mutex,
99		    PCATCH, "drmlk2", 0);
100		if (ret == -ERESTART)
101			ret = -ERESTARTSYS;
102		if (ret != 0)
103			break;
104	}
105	mtx_lock(&master->lock.spinlock);
106	master->lock.user_waiters--;
107	mtx_unlock(&master->lock.spinlock);
108
109	DRM_DEBUG("%d %s\n", lock->context,
110		  ret ? "interrupted" : "has lock");
111	if (ret) return ret;
112
113#if defined(__linux__)
114	/* don't set the block all signals on the master process for now
115	 * really probably not the correct answer but lets us debug xkb
116 	 * xserver for now */
117	if (!file_priv->is_master) {
118		sigemptyset(&dev->sigmask);
119		sigaddset(&dev->sigmask, SIGSTOP);
120		sigaddset(&dev->sigmask, SIGTSTP);
121		sigaddset(&dev->sigmask, SIGTTIN);
122		sigaddset(&dev->sigmask, SIGTTOU);
123		dev->sigdata.context = lock->context;
124		dev->sigdata.lock = master->lock.hw_lock;
125		block_all_signals(drm_notifier, &dev->sigdata, &dev->sigmask);
126	}
127#endif
128
129	if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT))
130	{
131		if (dev->driver->dma_quiescent(dev)) {
132			DRM_DEBUG("%d waiting for DMA quiescent\n",
133				  lock->context);
134			return -EBUSY;
135		}
136	}
137
138	return 0;
139}
140
141/**
142 * Unlock ioctl.
143 *
144 * \param inode device inode.
145 * \param file_priv DRM file private.
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 drm_device *dev, void *data, struct drm_file *file_priv)
153{
154	struct drm_lock *lock = data;
155	struct drm_master *master = file_priv->master;
156
157	if (lock->context == DRM_KERNEL_CONTEXT) {
158		DRM_ERROR("Process %d using kernel context %d\n",
159			  DRM_CURRENTPID, lock->context);
160		return -EINVAL;
161	}
162
163	atomic_inc(&dev->counts[_DRM_STAT_UNLOCKS]);
164
165	if (drm_lock_free(&master->lock, lock->context)) {
166		/* FIXME: Should really bail out here. */
167	}
168
169#if defined(__linux__)
170	unblock_all_signals();
171#endif
172	return 0;
173}
174
175/**
176 * Take the heavyweight lock.
177 *
178 * \param lock lock pointer.
179 * \param context locking context.
180 * \return one if the lock is held, or zero otherwise.
181 *
182 * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
183 */
184static
185int drm_lock_take(struct drm_lock_data *lock_data,
186		  unsigned int context)
187{
188	unsigned int old, new, prev;
189	volatile unsigned int *lock = &lock_data->hw_lock->lock;
190
191	mtx_lock(&lock_data->spinlock);
192	do {
193		old = *lock;
194		if (old & _DRM_LOCK_HELD)
195			new = old | _DRM_LOCK_CONT;
196		else {
197			new = context | _DRM_LOCK_HELD |
198				((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
199				 _DRM_LOCK_CONT : 0);
200		}
201		prev = cmpxchg(lock, old, new);
202	} while (prev != old);
203	mtx_unlock(&lock_data->spinlock);
204
205	if (_DRM_LOCKING_CONTEXT(old) == context) {
206		if (old & _DRM_LOCK_HELD) {
207			if (context != DRM_KERNEL_CONTEXT) {
208				DRM_ERROR("%d holds heavyweight lock\n",
209					  context);
210			}
211			return 0;
212		}
213	}
214
215	if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) {
216		/* Have lock */
217		return 1;
218	}
219	return 0;
220}
221
222/**
223 * This takes a lock forcibly and hands it to context.	Should ONLY be used
224 * inside *_unlock to give lock to kernel before calling *_dma_schedule.
225 *
226 * \param dev DRM device.
227 * \param lock lock pointer.
228 * \param context locking context.
229 * \return always one.
230 *
231 * Resets the lock file pointer.
232 * Marks the lock as held by the given context, via the \p cmpxchg instruction.
233 */
234static int drm_lock_transfer(struct drm_lock_data *lock_data,
235			     unsigned int context)
236{
237	unsigned int old, new, prev;
238	volatile unsigned int *lock = &lock_data->hw_lock->lock;
239
240	lock_data->file_priv = NULL;
241	do {
242		old = *lock;
243		new = context | _DRM_LOCK_HELD;
244		prev = cmpxchg(lock, old, new);
245	} while (prev != old);
246	return 1;
247}
248
249/**
250 * Free lock.
251 *
252 * \param dev DRM device.
253 * \param lock lock.
254 * \param context context.
255 *
256 * Resets the lock file pointer.
257 * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
258 * waiting on the lock queue.
259 */
260int drm_lock_free(struct drm_lock_data *lock_data, unsigned int context)
261{
262	unsigned int old, new, prev;
263	volatile unsigned int *lock = &lock_data->hw_lock->lock;
264
265	mtx_lock(&lock_data->spinlock);
266	if (lock_data->kernel_waiters != 0) {
267		drm_lock_transfer(lock_data, 0);
268		lock_data->idle_has_lock = 1;
269		mtx_unlock(&lock_data->spinlock);
270		return 1;
271	}
272	mtx_unlock(&lock_data->spinlock);
273
274	do {
275		old = *lock;
276		new = _DRM_LOCKING_CONTEXT(old);
277		prev = cmpxchg(lock, old, new);
278	} while (prev != old);
279
280	if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
281		DRM_ERROR("%d freed heavyweight lock held by %d\n",
282			  context, _DRM_LOCKING_CONTEXT(old));
283		return 1;
284	}
285	wake_up_interruptible(&lock_data->lock_queue);
286	return 0;
287}
288
289#if defined(__linux__)
290/**
291 * If we get here, it means that the process has called DRM_IOCTL_LOCK
292 * without calling DRM_IOCTL_UNLOCK.
293 *
294 * If the lock is not held, then let the signal proceed as usual.  If the lock
295 * is held, then set the contended flag and keep the signal blocked.
296 *
297 * \param priv pointer to a drm_sigdata structure.
298 * \return one if the signal should be delivered normally, or zero if the
299 * signal should be blocked.
300 */
301static int drm_notifier(void *priv)
302{
303	struct drm_sigdata *s = (struct drm_sigdata *) priv;
304	unsigned int old, new, prev;
305
306	/* Allow signal delivery if lock isn't held */
307	if (!s->lock || !_DRM_LOCK_IS_HELD(s->lock->lock)
308	    || _DRM_LOCKING_CONTEXT(s->lock->lock) != s->context)
309		return 1;
310
311	/* Otherwise, set flag to force call to
312	   drmUnlock */
313	do {
314		old = s->lock->lock;
315		new = old | _DRM_LOCK_CONT;
316		prev = cmpxchg(&s->lock->lock, old, new);
317	} while (prev != old);
318	return 0;
319}
320#endif
321
322/**
323 * This function returns immediately and takes the hw lock
324 * with the kernel context if it is free, otherwise it gets the highest priority when and if
325 * it is eventually released.
326 *
327 * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held
328 * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause
329 * a deadlock, which is why the "idlelock" was invented).
330 *
331 * This should be sufficient to wait for GPU idle without
332 * having to worry about starvation.
333 */
334
335void drm_idlelock_take(struct drm_lock_data *lock_data)
336{
337	int ret;
338
339	mtx_lock(&lock_data->spinlock);
340	lock_data->kernel_waiters++;
341	if (!lock_data->idle_has_lock) {
342
343		mtx_unlock(&lock_data->spinlock);
344		ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
345		mtx_lock(&lock_data->spinlock);
346
347		if (ret == 1)
348			lock_data->idle_has_lock = 1;
349	}
350	mtx_unlock(&lock_data->spinlock);
351}
352EXPORT_SYMBOL(drm_idlelock_take);
353
354void drm_idlelock_release(struct drm_lock_data *lock_data)
355{
356	unsigned int old, prev;
357	volatile unsigned int *lock = &lock_data->hw_lock->lock;
358
359	mtx_lock(&lock_data->spinlock);
360	if (--lock_data->kernel_waiters == 0) {
361		if (lock_data->idle_has_lock) {
362			do {
363				old = *lock;
364				prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT);
365			} while (prev != old);
366			wake_up_interruptible(&lock_data->lock_queue);
367			lock_data->idle_has_lock = 0;
368		}
369	}
370	mtx_unlock(&lock_data->spinlock);
371}
372EXPORT_SYMBOL(drm_idlelock_release);
373
374int drm_i_have_hw_lock(struct drm_device *dev, struct drm_file *file_priv)
375{
376	struct drm_master *master = file_priv->master;
377	return (file_priv->lock_count && master->lock.hw_lock &&
378		_DRM_LOCK_IS_HELD(master->lock.hw_lock->lock) &&
379		master->lock.file_priv == file_priv);
380}
381