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 <linux/export.h>
37#include <drm/drmP.h>
38#include "drm_legacy.h"
39#include "drm_internal.h"
40
41static int drm_notifier(void *priv);
42
43static int drm_lock_take(struct drm_lock_data *lock_data, unsigned int context);
44
45/**
46 * Lock ioctl.
47 *
48 * \param inode device inode.
49 * \param file_priv DRM file private.
50 * \param cmd command.
51 * \param arg user argument, pointing to a drm_lock structure.
52 * \return zero on success or negative number on failure.
53 *
54 * Add the current task to the lock wait queue, and attempt to take to lock.
55 */
56int drm_legacy_lock(struct drm_device *dev, void *data,
57		    struct drm_file *file_priv)
58{
59	DECLARE_WAITQUEUE(entry, current);
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			  task_pid_nr(current), lock->context);
69		return -EINVAL;
70	}
71
72	DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
73		  lock->context, task_pid_nr(current),
74		  master->lock.hw_lock->lock, lock->flags);
75
76	add_wait_queue(&master->lock.lock_queue, &entry);
77	spin_lock_bh(&master->lock.spinlock);
78	master->lock.user_waiters++;
79	spin_unlock_bh(&master->lock.spinlock);
80
81	for (;;) {
82		__set_current_state(TASK_INTERRUPTIBLE);
83		if (!master->lock.hw_lock) {
84			/* Device has been unregistered */
85			send_sig(SIGTERM, current, 0);
86			ret = -EINTR;
87			break;
88		}
89		if (drm_lock_take(&master->lock, lock->context)) {
90			master->lock.file_priv = file_priv;
91			master->lock.lock_time = jiffies;
92			break;	/* Got lock */
93		}
94
95		/* Contention */
96		mutex_unlock(&drm_global_mutex);
97		schedule();
98		mutex_lock(&drm_global_mutex);
99		if (signal_pending(current)) {
100			ret = -EINTR;
101			break;
102		}
103	}
104	spin_lock_bh(&master->lock.spinlock);
105	master->lock.user_waiters--;
106	spin_unlock_bh(&master->lock.spinlock);
107	__set_current_state(TASK_RUNNING);
108	remove_wait_queue(&master->lock.lock_queue, &entry);
109
110	DRM_DEBUG("%d %s\n", lock->context,
111		  ret ? "interrupted" : "has lock");
112	if (ret) return ret;
113
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, &dev->sigmask);
126	}
127
128	if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT))
129	{
130		if (dev->driver->dma_quiescent(dev)) {
131			DRM_DEBUG("%d waiting for DMA quiescent\n",
132				  lock->context);
133			return -EBUSY;
134		}
135	}
136
137	return 0;
138}
139
140/**
141 * Unlock ioctl.
142 *
143 * \param inode device inode.
144 * \param file_priv DRM file private.
145 * \param cmd command.
146 * \param arg user argument, pointing to a drm_lock structure.
147 * \return zero on success or negative number on failure.
148 *
149 * Transfer and free the lock.
150 */
151int drm_legacy_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv)
152{
153	struct drm_lock *lock = data;
154	struct drm_master *master = file_priv->master;
155
156	if (lock->context == DRM_KERNEL_CONTEXT) {
157		DRM_ERROR("Process %d using kernel context %d\n",
158			  task_pid_nr(current), lock->context);
159		return -EINVAL;
160	}
161
162	if (drm_legacy_lock_free(&master->lock, lock->context)) {
163		/* FIXME: Should really bail out here. */
164	}
165
166	unblock_all_signals();
167	return 0;
168}
169
170/**
171 * Take the heavyweight lock.
172 *
173 * \param lock lock pointer.
174 * \param context locking context.
175 * \return one if the lock is held, or zero otherwise.
176 *
177 * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
178 */
179static
180int drm_lock_take(struct drm_lock_data *lock_data,
181		  unsigned int context)
182{
183	unsigned int old, new, prev;
184	volatile unsigned int *lock = &lock_data->hw_lock->lock;
185
186	spin_lock_bh(&lock_data->spinlock);
187	do {
188		old = *lock;
189		if (old & _DRM_LOCK_HELD)
190			new = old | _DRM_LOCK_CONT;
191		else {
192			new = context | _DRM_LOCK_HELD |
193				((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
194				 _DRM_LOCK_CONT : 0);
195		}
196		prev = cmpxchg(lock, old, new);
197	} while (prev != old);
198	spin_unlock_bh(&lock_data->spinlock);
199
200	if (_DRM_LOCKING_CONTEXT(old) == context) {
201		if (old & _DRM_LOCK_HELD) {
202			if (context != DRM_KERNEL_CONTEXT) {
203				DRM_ERROR("%d holds heavyweight lock\n",
204					  context);
205			}
206			return 0;
207		}
208	}
209
210	if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) {
211		/* Have lock */
212		return 1;
213	}
214	return 0;
215}
216
217/**
218 * This takes a lock forcibly and hands it to context.	Should ONLY be used
219 * inside *_unlock to give lock to kernel before calling *_dma_schedule.
220 *
221 * \param dev DRM device.
222 * \param lock lock pointer.
223 * \param context locking context.
224 * \return always one.
225 *
226 * Resets the lock file pointer.
227 * Marks the lock as held by the given context, via the \p cmpxchg instruction.
228 */
229static int drm_lock_transfer(struct drm_lock_data *lock_data,
230			     unsigned int context)
231{
232	unsigned int old, new, prev;
233	volatile unsigned int *lock = &lock_data->hw_lock->lock;
234
235	lock_data->file_priv = NULL;
236	do {
237		old = *lock;
238		new = context | _DRM_LOCK_HELD;
239		prev = cmpxchg(lock, old, new);
240	} while (prev != old);
241	return 1;
242}
243
244/**
245 * Free lock.
246 *
247 * \param dev DRM device.
248 * \param lock lock.
249 * \param context context.
250 *
251 * Resets the lock file pointer.
252 * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
253 * waiting on the lock queue.
254 */
255int drm_legacy_lock_free(struct drm_lock_data *lock_data, unsigned int context)
256{
257	unsigned int old, new, prev;
258	volatile unsigned int *lock = &lock_data->hw_lock->lock;
259
260	spin_lock_bh(&lock_data->spinlock);
261	if (lock_data->kernel_waiters != 0) {
262		drm_lock_transfer(lock_data, 0);
263		lock_data->idle_has_lock = 1;
264		spin_unlock_bh(&lock_data->spinlock);
265		return 1;
266	}
267	spin_unlock_bh(&lock_data->spinlock);
268
269	do {
270		old = *lock;
271		new = _DRM_LOCKING_CONTEXT(old);
272		prev = cmpxchg(lock, old, new);
273	} while (prev != old);
274
275	if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
276		DRM_ERROR("%d freed heavyweight lock held by %d\n",
277			  context, _DRM_LOCKING_CONTEXT(old));
278		return 1;
279	}
280	wake_up_interruptible(&lock_data->lock_queue);
281	return 0;
282}
283
284/**
285 * If we get here, it means that the process has called DRM_IOCTL_LOCK
286 * without calling DRM_IOCTL_UNLOCK.
287 *
288 * If the lock is not held, then let the signal proceed as usual.  If the lock
289 * is held, then set the contended flag and keep the signal blocked.
290 *
291 * \param priv pointer to a drm_device structure.
292 * \return one if the signal should be delivered normally, or zero if the
293 * signal should be blocked.
294 */
295static int drm_notifier(void *priv)
296{
297	struct drm_device *dev = priv;
298	struct drm_hw_lock *lock = dev->sigdata.lock;
299	unsigned int old, new, prev;
300
301	/* Allow signal delivery if lock isn't held */
302	if (!lock || !_DRM_LOCK_IS_HELD(lock->lock)
303	    || _DRM_LOCKING_CONTEXT(lock->lock) != dev->sigdata.context)
304		return 1;
305
306	/* Otherwise, set flag to force call to
307	   drmUnlock */
308	do {
309		old = lock->lock;
310		new = old | _DRM_LOCK_CONT;
311		prev = cmpxchg(&lock->lock, old, new);
312	} while (prev != old);
313	return 0;
314}
315
316/**
317 * This function returns immediately and takes the hw lock
318 * with the kernel context if it is free, otherwise it gets the highest priority when and if
319 * it is eventually released.
320 *
321 * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held
322 * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause
323 * a deadlock, which is why the "idlelock" was invented).
324 *
325 * This should be sufficient to wait for GPU idle without
326 * having to worry about starvation.
327 */
328
329void drm_legacy_idlelock_take(struct drm_lock_data *lock_data)
330{
331	int ret;
332
333	spin_lock_bh(&lock_data->spinlock);
334	lock_data->kernel_waiters++;
335	if (!lock_data->idle_has_lock) {
336
337		spin_unlock_bh(&lock_data->spinlock);
338		ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
339		spin_lock_bh(&lock_data->spinlock);
340
341		if (ret == 1)
342			lock_data->idle_has_lock = 1;
343	}
344	spin_unlock_bh(&lock_data->spinlock);
345}
346EXPORT_SYMBOL(drm_legacy_idlelock_take);
347
348void drm_legacy_idlelock_release(struct drm_lock_data *lock_data)
349{
350	unsigned int old, prev;
351	volatile unsigned int *lock = &lock_data->hw_lock->lock;
352
353	spin_lock_bh(&lock_data->spinlock);
354	if (--lock_data->kernel_waiters == 0) {
355		if (lock_data->idle_has_lock) {
356			do {
357				old = *lock;
358				prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT);
359			} while (prev != old);
360			wake_up_interruptible(&lock_data->lock_queue);
361			lock_data->idle_has_lock = 0;
362		}
363	}
364	spin_unlock_bh(&lock_data->spinlock);
365}
366EXPORT_SYMBOL(drm_legacy_idlelock_release);
367
368int drm_legacy_i_have_hw_lock(struct drm_device *dev,
369			      struct drm_file *file_priv)
370{
371	struct drm_master *master = file_priv->master;
372	return (file_priv->lock_count && master->lock.hw_lock &&
373		_DRM_LOCK_IS_HELD(master->lock.hw_lock->lock) &&
374		master->lock.file_priv == file_priv);
375}
376