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	if (drm_core_check_feature(dev, DRIVER_MODESET))
65		return -EINVAL;
66
67	++file_priv->lock_count;
68
69	if (lock->context == DRM_KERNEL_CONTEXT) {
70		DRM_ERROR("Process %d using kernel context %d\n",
71			  task_pid_nr(current), lock->context);
72		return -EINVAL;
73	}
74
75	DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
76		  lock->context, task_pid_nr(current),
77		  master->lock.hw_lock->lock, lock->flags);
78
79	add_wait_queue(&master->lock.lock_queue, &entry);
80	spin_lock_bh(&master->lock.spinlock);
81	master->lock.user_waiters++;
82	spin_unlock_bh(&master->lock.spinlock);
83
84	for (;;) {
85		__set_current_state(TASK_INTERRUPTIBLE);
86		if (!master->lock.hw_lock) {
87			/* Device has been unregistered */
88			send_sig(SIGTERM, current, 0);
89			ret = -EINTR;
90			break;
91		}
92		if (drm_lock_take(&master->lock, lock->context)) {
93			master->lock.file_priv = file_priv;
94			master->lock.lock_time = jiffies;
95			break;	/* Got lock */
96		}
97
98		/* Contention */
99		mutex_unlock(&drm_global_mutex);
100		schedule();
101		mutex_lock(&drm_global_mutex);
102		if (signal_pending(current)) {
103			ret = -EINTR;
104			break;
105		}
106	}
107	spin_lock_bh(&master->lock.spinlock);
108	master->lock.user_waiters--;
109	spin_unlock_bh(&master->lock.spinlock);
110	__set_current_state(TASK_RUNNING);
111	remove_wait_queue(&master->lock.lock_queue, &entry);
112
113	DRM_DEBUG("%d %s\n", lock->context,
114		  ret ? "interrupted" : "has lock");
115	if (ret) return ret;
116
117	/* don't set the block all signals on the master process for now
118	 * really probably not the correct answer but lets us debug xkb
119 	 * xserver for now */
120	if (!file_priv->is_master) {
121		sigemptyset(&dev->sigmask);
122		sigaddset(&dev->sigmask, SIGSTOP);
123		sigaddset(&dev->sigmask, SIGTSTP);
124		sigaddset(&dev->sigmask, SIGTTIN);
125		sigaddset(&dev->sigmask, SIGTTOU);
126		dev->sigdata.context = lock->context;
127		dev->sigdata.lock = master->lock.hw_lock;
128		block_all_signals(drm_notifier, dev, &dev->sigmask);
129	}
130
131	if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT))
132	{
133		if (dev->driver->dma_quiescent(dev)) {
134			DRM_DEBUG("%d waiting for DMA quiescent\n",
135				  lock->context);
136			return -EBUSY;
137		}
138	}
139
140	return 0;
141}
142
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 */
154int drm_legacy_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv)
155{
156	struct drm_lock *lock = data;
157	struct drm_master *master = file_priv->master;
158
159	if (drm_core_check_feature(dev, DRIVER_MODESET))
160		return -EINVAL;
161
162	if (lock->context == DRM_KERNEL_CONTEXT) {
163		DRM_ERROR("Process %d using kernel context %d\n",
164			  task_pid_nr(current), lock->context);
165		return -EINVAL;
166	}
167
168	if (drm_legacy_lock_free(&master->lock, lock->context)) {
169		/* FIXME: Should really bail out here. */
170	}
171
172	unblock_all_signals();
173	return 0;
174}
175
176/**
177 * Take the heavyweight lock.
178 *
179 * \param lock lock pointer.
180 * \param context locking context.
181 * \return one if the lock is held, or zero otherwise.
182 *
183 * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
184 */
185static
186int drm_lock_take(struct drm_lock_data *lock_data,
187		  unsigned int context)
188{
189	unsigned int old, new, prev;
190	volatile unsigned int *lock = &lock_data->hw_lock->lock;
191
192	spin_lock_bh(&lock_data->spinlock);
193	do {
194		old = *lock;
195		if (old & _DRM_LOCK_HELD)
196			new = old | _DRM_LOCK_CONT;
197		else {
198			new = context | _DRM_LOCK_HELD |
199				((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
200				 _DRM_LOCK_CONT : 0);
201		}
202		prev = cmpxchg(lock, old, new);
203	} while (prev != old);
204	spin_unlock_bh(&lock_data->spinlock);
205
206	if (_DRM_LOCKING_CONTEXT(old) == context) {
207		if (old & _DRM_LOCK_HELD) {
208			if (context != DRM_KERNEL_CONTEXT) {
209				DRM_ERROR("%d holds heavyweight lock\n",
210					  context);
211			}
212			return 0;
213		}
214	}
215
216	if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) {
217		/* Have lock */
218		return 1;
219	}
220	return 0;
221}
222
223/**
224 * This takes a lock forcibly and hands it to context.	Should ONLY be used
225 * inside *_unlock to give lock to kernel before calling *_dma_schedule.
226 *
227 * \param dev DRM device.
228 * \param lock lock pointer.
229 * \param context locking context.
230 * \return always one.
231 *
232 * Resets the lock file pointer.
233 * Marks the lock as held by the given context, via the \p cmpxchg instruction.
234 */
235static int drm_lock_transfer(struct drm_lock_data *lock_data,
236			     unsigned int context)
237{
238	unsigned int old, new, prev;
239	volatile unsigned int *lock = &lock_data->hw_lock->lock;
240
241	lock_data->file_priv = NULL;
242	do {
243		old = *lock;
244		new = context | _DRM_LOCK_HELD;
245		prev = cmpxchg(lock, old, new);
246	} while (prev != old);
247	return 1;
248}
249
250/**
251 * Free lock.
252 *
253 * \param dev DRM device.
254 * \param lock lock.
255 * \param context context.
256 *
257 * Resets the lock file pointer.
258 * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
259 * waiting on the lock queue.
260 */
261int drm_legacy_lock_free(struct drm_lock_data *lock_data, unsigned int context)
262{
263	unsigned int old, new, prev;
264	volatile unsigned int *lock = &lock_data->hw_lock->lock;
265
266	spin_lock_bh(&lock_data->spinlock);
267	if (lock_data->kernel_waiters != 0) {
268		drm_lock_transfer(lock_data, 0);
269		lock_data->idle_has_lock = 1;
270		spin_unlock_bh(&lock_data->spinlock);
271		return 1;
272	}
273	spin_unlock_bh(&lock_data->spinlock);
274
275	do {
276		old = *lock;
277		new = _DRM_LOCKING_CONTEXT(old);
278		prev = cmpxchg(lock, old, new);
279	} while (prev != old);
280
281	if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
282		DRM_ERROR("%d freed heavyweight lock held by %d\n",
283			  context, _DRM_LOCKING_CONTEXT(old));
284		return 1;
285	}
286	wake_up_interruptible(&lock_data->lock_queue);
287	return 0;
288}
289
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_device 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_device *dev = priv;
304	struct drm_hw_lock *lock = dev->sigdata.lock;
305	unsigned int old, new, prev;
306
307	/* Allow signal delivery if lock isn't held */
308	if (!lock || !_DRM_LOCK_IS_HELD(lock->lock)
309	    || _DRM_LOCKING_CONTEXT(lock->lock) != dev->sigdata.context)
310		return 1;
311
312	/* Otherwise, set flag to force call to
313	   drmUnlock */
314	do {
315		old = lock->lock;
316		new = old | _DRM_LOCK_CONT;
317		prev = cmpxchg(&lock->lock, old, new);
318	} while (prev != old);
319	return 0;
320}
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_legacy_idlelock_take(struct drm_lock_data *lock_data)
336{
337	int ret;
338
339	spin_lock_bh(&lock_data->spinlock);
340	lock_data->kernel_waiters++;
341	if (!lock_data->idle_has_lock) {
342
343		spin_unlock_bh(&lock_data->spinlock);
344		ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
345		spin_lock_bh(&lock_data->spinlock);
346
347		if (ret == 1)
348			lock_data->idle_has_lock = 1;
349	}
350	spin_unlock_bh(&lock_data->spinlock);
351}
352EXPORT_SYMBOL(drm_legacy_idlelock_take);
353
354void drm_legacy_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	spin_lock_bh(&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	spin_unlock_bh(&lock_data->spinlock);
371}
372EXPORT_SYMBOL(drm_legacy_idlelock_release);
373
374int drm_legacy_i_have_hw_lock(struct drm_device *dev,
375			      struct drm_file *file_priv)
376{
377	struct drm_master *master = file_priv->master;
378	return (file_priv->lock_count && master->lock.hw_lock &&
379		_DRM_LOCK_IS_HELD(master->lock.hw_lock->lock) &&
380		master->lock.file_priv == file_priv);
381}
382