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_lock_take(struct drm_lock_data *lock_data, unsigned int context);
42
43/**
44 * Lock ioctl.
45 *
46 * \param inode device inode.
47 * \param file_priv DRM file private.
48 * \param cmd command.
49 * \param arg user argument, pointing to a drm_lock structure.
50 * \return zero on success or negative number on failure.
51 *
52 * Add the current task to the lock wait queue, and attempt to take to lock.
53 */
54int drm_legacy_lock(struct drm_device *dev, void *data,
55		    struct drm_file *file_priv)
56{
57	DECLARE_WAITQUEUE(entry, current);
58	struct drm_lock *lock = data;
59	struct drm_master *master = file_priv->master;
60	int ret = 0;
61
62	if (drm_core_check_feature(dev, DRIVER_MODESET))
63		return -EINVAL;
64
65	++file_priv->lock_count;
66
67	if (lock->context == DRM_KERNEL_CONTEXT) {
68		DRM_ERROR("Process %d using kernel context %d\n",
69			  task_pid_nr(current), lock->context);
70		return -EINVAL;
71	}
72
73	DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
74		  lock->context, task_pid_nr(current),
75		  master->lock.hw_lock->lock, lock->flags);
76
77	add_wait_queue(&master->lock.lock_queue, &entry);
78	spin_lock_bh(&master->lock.spinlock);
79	master->lock.user_waiters++;
80	spin_unlock_bh(&master->lock.spinlock);
81
82	for (;;) {
83		__set_current_state(TASK_INTERRUPTIBLE);
84		if (!master->lock.hw_lock) {
85			/* Device has been unregistered */
86			send_sig(SIGTERM, current, 0);
87			ret = -EINTR;
88			break;
89		}
90		if (drm_lock_take(&master->lock, lock->context)) {
91			master->lock.file_priv = file_priv;
92			master->lock.lock_time = jiffies;
93			break;	/* Got lock */
94		}
95
96		/* Contention */
97		mutex_unlock(&drm_global_mutex);
98		schedule();
99		mutex_lock(&drm_global_mutex);
100		if (signal_pending(current)) {
101			ret = -EINTR;
102			break;
103		}
104	}
105	spin_lock_bh(&master->lock.spinlock);
106	master->lock.user_waiters--;
107	spin_unlock_bh(&master->lock.spinlock);
108	__set_current_state(TASK_RUNNING);
109	remove_wait_queue(&master->lock.lock_queue, &entry);
110
111	DRM_DEBUG("%d %s\n", lock->context,
112		  ret ? "interrupted" : "has lock");
113	if (ret) return ret;
114
115	/* don't set the block all signals on the master process for now
116	 * really probably not the correct answer but lets us debug xkb
117 	 * xserver for now */
118	if (!file_priv->is_master) {
119		dev->sigdata.context = lock->context;
120		dev->sigdata.lock = master->lock.hw_lock;
121	}
122
123	if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT))
124	{
125		if (dev->driver->dma_quiescent(dev)) {
126			DRM_DEBUG("%d waiting for DMA quiescent\n",
127				  lock->context);
128			return -EBUSY;
129		}
130	}
131
132	return 0;
133}
134
135/**
136 * Unlock ioctl.
137 *
138 * \param inode device inode.
139 * \param file_priv DRM file private.
140 * \param cmd command.
141 * \param arg user argument, pointing to a drm_lock structure.
142 * \return zero on success or negative number on failure.
143 *
144 * Transfer and free the lock.
145 */
146int drm_legacy_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv)
147{
148	struct drm_lock *lock = data;
149	struct drm_master *master = file_priv->master;
150
151	if (drm_core_check_feature(dev, DRIVER_MODESET))
152		return -EINVAL;
153
154	if (lock->context == DRM_KERNEL_CONTEXT) {
155		DRM_ERROR("Process %d using kernel context %d\n",
156			  task_pid_nr(current), lock->context);
157		return -EINVAL;
158	}
159
160	if (drm_legacy_lock_free(&master->lock, lock->context)) {
161		/* FIXME: Should really bail out here. */
162	}
163
164	return 0;
165}
166
167/**
168 * Take the heavyweight lock.
169 *
170 * \param lock lock pointer.
171 * \param context locking context.
172 * \return one if the lock is held, or zero otherwise.
173 *
174 * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
175 */
176static
177int drm_lock_take(struct drm_lock_data *lock_data,
178		  unsigned int context)
179{
180	unsigned int old, new, prev;
181	volatile unsigned int *lock = &lock_data->hw_lock->lock;
182
183	spin_lock_bh(&lock_data->spinlock);
184	do {
185		old = *lock;
186		if (old & _DRM_LOCK_HELD)
187			new = old | _DRM_LOCK_CONT;
188		else {
189			new = context | _DRM_LOCK_HELD |
190				((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
191				 _DRM_LOCK_CONT : 0);
192		}
193		prev = cmpxchg(lock, old, new);
194	} while (prev != old);
195	spin_unlock_bh(&lock_data->spinlock);
196
197	if (_DRM_LOCKING_CONTEXT(old) == context) {
198		if (old & _DRM_LOCK_HELD) {
199			if (context != DRM_KERNEL_CONTEXT) {
200				DRM_ERROR("%d holds heavyweight lock\n",
201					  context);
202			}
203			return 0;
204		}
205	}
206
207	if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) {
208		/* Have lock */
209		return 1;
210	}
211	return 0;
212}
213
214/**
215 * This takes a lock forcibly and hands it to context.	Should ONLY be used
216 * inside *_unlock to give lock to kernel before calling *_dma_schedule.
217 *
218 * \param dev DRM device.
219 * \param lock lock pointer.
220 * \param context locking context.
221 * \return always one.
222 *
223 * Resets the lock file pointer.
224 * Marks the lock as held by the given context, via the \p cmpxchg instruction.
225 */
226static int drm_lock_transfer(struct drm_lock_data *lock_data,
227			     unsigned int context)
228{
229	unsigned int old, new, prev;
230	volatile unsigned int *lock = &lock_data->hw_lock->lock;
231
232	lock_data->file_priv = NULL;
233	do {
234		old = *lock;
235		new = context | _DRM_LOCK_HELD;
236		prev = cmpxchg(lock, old, new);
237	} while (prev != old);
238	return 1;
239}
240
241/**
242 * Free lock.
243 *
244 * \param dev DRM device.
245 * \param lock lock.
246 * \param context context.
247 *
248 * Resets the lock file pointer.
249 * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
250 * waiting on the lock queue.
251 */
252int drm_legacy_lock_free(struct drm_lock_data *lock_data, unsigned int context)
253{
254	unsigned int old, new, prev;
255	volatile unsigned int *lock = &lock_data->hw_lock->lock;
256
257	spin_lock_bh(&lock_data->spinlock);
258	if (lock_data->kernel_waiters != 0) {
259		drm_lock_transfer(lock_data, 0);
260		lock_data->idle_has_lock = 1;
261		spin_unlock_bh(&lock_data->spinlock);
262		return 1;
263	}
264	spin_unlock_bh(&lock_data->spinlock);
265
266	do {
267		old = *lock;
268		new = _DRM_LOCKING_CONTEXT(old);
269		prev = cmpxchg(lock, old, new);
270	} while (prev != old);
271
272	if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
273		DRM_ERROR("%d freed heavyweight lock held by %d\n",
274			  context, _DRM_LOCKING_CONTEXT(old));
275		return 1;
276	}
277	wake_up_interruptible(&lock_data->lock_queue);
278	return 0;
279}
280
281/**
282 * This function returns immediately and takes the hw lock
283 * with the kernel context if it is free, otherwise it gets the highest priority when and if
284 * it is eventually released.
285 *
286 * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held
287 * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause
288 * a deadlock, which is why the "idlelock" was invented).
289 *
290 * This should be sufficient to wait for GPU idle without
291 * having to worry about starvation.
292 */
293
294void drm_legacy_idlelock_take(struct drm_lock_data *lock_data)
295{
296	int ret;
297
298	spin_lock_bh(&lock_data->spinlock);
299	lock_data->kernel_waiters++;
300	if (!lock_data->idle_has_lock) {
301
302		spin_unlock_bh(&lock_data->spinlock);
303		ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
304		spin_lock_bh(&lock_data->spinlock);
305
306		if (ret == 1)
307			lock_data->idle_has_lock = 1;
308	}
309	spin_unlock_bh(&lock_data->spinlock);
310}
311EXPORT_SYMBOL(drm_legacy_idlelock_take);
312
313void drm_legacy_idlelock_release(struct drm_lock_data *lock_data)
314{
315	unsigned int old, prev;
316	volatile unsigned int *lock = &lock_data->hw_lock->lock;
317
318	spin_lock_bh(&lock_data->spinlock);
319	if (--lock_data->kernel_waiters == 0) {
320		if (lock_data->idle_has_lock) {
321			do {
322				old = *lock;
323				prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT);
324			} while (prev != old);
325			wake_up_interruptible(&lock_data->lock_queue);
326			lock_data->idle_has_lock = 0;
327		}
328	}
329	spin_unlock_bh(&lock_data->spinlock);
330}
331EXPORT_SYMBOL(drm_legacy_idlelock_release);
332
333int drm_legacy_i_have_hw_lock(struct drm_device *dev,
334			      struct drm_file *file_priv)
335{
336	struct drm_master *master = file_priv->master;
337	return (file_priv->lock_count && master->lock.hw_lock &&
338		_DRM_LOCK_IS_HELD(master->lock.hw_lock->lock) &&
339		master->lock.file_priv == file_priv);
340}
341