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
41 static int drm_lock_take(struct drm_lock_data *lock_data, unsigned int context);
42
43 /**
44 * Take the heavyweight lock.
45 *
46 * \param lock lock pointer.
47 * \param context locking context.
48 * \return one if the lock is held, or zero otherwise.
49 *
50 * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
51 */
52 static
drm_lock_take(struct drm_lock_data * lock_data,unsigned int context)53 int drm_lock_take(struct drm_lock_data *lock_data,
54 unsigned int context)
55 {
56 unsigned int old, new, prev;
57 volatile unsigned int *lock = &lock_data->hw_lock->lock;
58
59 spin_lock_bh(&lock_data->spinlock);
60 do {
61 old = *lock;
62 if (old & _DRM_LOCK_HELD)
63 new = old | _DRM_LOCK_CONT;
64 else {
65 new = context | _DRM_LOCK_HELD |
66 ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
67 _DRM_LOCK_CONT : 0);
68 }
69 prev = cmpxchg(lock, old, new);
70 } while (prev != old);
71 spin_unlock_bh(&lock_data->spinlock);
72
73 if (_DRM_LOCKING_CONTEXT(old) == context) {
74 if (old & _DRM_LOCK_HELD) {
75 if (context != DRM_KERNEL_CONTEXT) {
76 DRM_ERROR("%d holds heavyweight lock\n",
77 context);
78 }
79 return 0;
80 }
81 }
82
83 if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) {
84 /* Have lock */
85 return 1;
86 }
87 return 0;
88 }
89
90 /**
91 * This takes a lock forcibly and hands it to context. Should ONLY be used
92 * inside *_unlock to give lock to kernel before calling *_dma_schedule.
93 *
94 * \param dev DRM device.
95 * \param lock lock pointer.
96 * \param context locking context.
97 * \return always one.
98 *
99 * Resets the lock file pointer.
100 * Marks the lock as held by the given context, via the \p cmpxchg instruction.
101 */
drm_lock_transfer(struct drm_lock_data * lock_data,unsigned int context)102 static int drm_lock_transfer(struct drm_lock_data *lock_data,
103 unsigned int context)
104 {
105 unsigned int old, new, prev;
106 volatile unsigned int *lock = &lock_data->hw_lock->lock;
107
108 lock_data->file_priv = NULL;
109 do {
110 old = *lock;
111 new = context | _DRM_LOCK_HELD;
112 prev = cmpxchg(lock, old, new);
113 } while (prev != old);
114 return 1;
115 }
116
drm_legacy_lock_free(struct drm_lock_data * lock_data,unsigned int context)117 static int drm_legacy_lock_free(struct drm_lock_data *lock_data,
118 unsigned int context)
119 {
120 unsigned int old, new, prev;
121 volatile unsigned int *lock = &lock_data->hw_lock->lock;
122
123 spin_lock_bh(&lock_data->spinlock);
124 if (lock_data->kernel_waiters != 0) {
125 drm_lock_transfer(lock_data, 0);
126 lock_data->idle_has_lock = 1;
127 spin_unlock_bh(&lock_data->spinlock);
128 return 1;
129 }
130 spin_unlock_bh(&lock_data->spinlock);
131
132 do {
133 old = *lock;
134 new = _DRM_LOCKING_CONTEXT(old);
135 prev = cmpxchg(lock, old, new);
136 } while (prev != old);
137
138 if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
139 DRM_ERROR("%d freed heavyweight lock held by %d\n",
140 context, _DRM_LOCKING_CONTEXT(old));
141 return 1;
142 }
143 wake_up_interruptible(&lock_data->lock_queue);
144 return 0;
145 }
146
147 /**
148 * Lock ioctl.
149 *
150 * \param inode device inode.
151 * \param file_priv DRM file private.
152 * \param cmd command.
153 * \param arg user argument, pointing to a drm_lock structure.
154 * \return zero on success or negative number on failure.
155 *
156 * Add the current task to the lock wait queue, and attempt to take to lock.
157 */
drm_legacy_lock(struct drm_device * dev,void * data,struct drm_file * file_priv)158 int drm_legacy_lock(struct drm_device *dev, void *data,
159 struct drm_file *file_priv)
160 {
161 DECLARE_WAITQUEUE(entry, current);
162 struct drm_lock *lock = data;
163 struct drm_master *master = file_priv->master;
164 int ret = 0;
165
166 if (!drm_core_check_feature(dev, DRIVER_LEGACY))
167 return -EINVAL;
168
169 ++file_priv->lock_count;
170
171 if (lock->context == DRM_KERNEL_CONTEXT) {
172 DRM_ERROR("Process %d using kernel context %d\n",
173 task_pid_nr(current), lock->context);
174 return -EINVAL;
175 }
176
177 DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
178 lock->context, task_pid_nr(current),
179 master->lock.hw_lock->lock, lock->flags);
180
181 add_wait_queue(&master->lock.lock_queue, &entry);
182 spin_lock_bh(&master->lock.spinlock);
183 master->lock.user_waiters++;
184 spin_unlock_bh(&master->lock.spinlock);
185
186 for (;;) {
187 __set_current_state(TASK_INTERRUPTIBLE);
188 if (!master->lock.hw_lock) {
189 /* Device has been unregistered */
190 send_sig(SIGTERM, current, 0);
191 ret = -EINTR;
192 break;
193 }
194 if (drm_lock_take(&master->lock, lock->context)) {
195 master->lock.file_priv = file_priv;
196 master->lock.lock_time = jiffies;
197 break; /* Got lock */
198 }
199
200 /* Contention */
201 mutex_unlock(&drm_global_mutex);
202 schedule();
203 mutex_lock(&drm_global_mutex);
204 if (signal_pending(current)) {
205 ret = -EINTR;
206 break;
207 }
208 }
209 spin_lock_bh(&master->lock.spinlock);
210 master->lock.user_waiters--;
211 spin_unlock_bh(&master->lock.spinlock);
212 __set_current_state(TASK_RUNNING);
213 remove_wait_queue(&master->lock.lock_queue, &entry);
214
215 DRM_DEBUG("%d %s\n", lock->context,
216 ret ? "interrupted" : "has lock");
217 if (ret) return ret;
218
219 /* don't set the block all signals on the master process for now
220 * really probably not the correct answer but lets us debug xkb
221 * xserver for now */
222 if (!drm_is_current_master(file_priv)) {
223 dev->sigdata.context = lock->context;
224 dev->sigdata.lock = master->lock.hw_lock;
225 }
226
227 if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT))
228 {
229 if (dev->driver->dma_quiescent(dev)) {
230 DRM_DEBUG("%d waiting for DMA quiescent\n",
231 lock->context);
232 return -EBUSY;
233 }
234 }
235
236 return 0;
237 }
238
239 /**
240 * Unlock ioctl.
241 *
242 * \param inode device inode.
243 * \param file_priv DRM file private.
244 * \param cmd command.
245 * \param arg user argument, pointing to a drm_lock structure.
246 * \return zero on success or negative number on failure.
247 *
248 * Transfer and free the lock.
249 */
drm_legacy_unlock(struct drm_device * dev,void * data,struct drm_file * file_priv)250 int drm_legacy_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv)
251 {
252 struct drm_lock *lock = data;
253 struct drm_master *master = file_priv->master;
254
255 if (!drm_core_check_feature(dev, DRIVER_LEGACY))
256 return -EINVAL;
257
258 if (lock->context == DRM_KERNEL_CONTEXT) {
259 DRM_ERROR("Process %d using kernel context %d\n",
260 task_pid_nr(current), lock->context);
261 return -EINVAL;
262 }
263
264 if (drm_legacy_lock_free(&master->lock, lock->context)) {
265 /* FIXME: Should really bail out here. */
266 }
267
268 return 0;
269 }
270
271 /**
272 * This function returns immediately and takes the hw lock
273 * with the kernel context if it is free, otherwise it gets the highest priority when and if
274 * it is eventually released.
275 *
276 * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held
277 * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause
278 * a deadlock, which is why the "idlelock" was invented).
279 *
280 * This should be sufficient to wait for GPU idle without
281 * having to worry about starvation.
282 */
283
drm_legacy_idlelock_take(struct drm_lock_data * lock_data)284 void drm_legacy_idlelock_take(struct drm_lock_data *lock_data)
285 {
286 int ret;
287
288 spin_lock_bh(&lock_data->spinlock);
289 lock_data->kernel_waiters++;
290 if (!lock_data->idle_has_lock) {
291
292 spin_unlock_bh(&lock_data->spinlock);
293 ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
294 spin_lock_bh(&lock_data->spinlock);
295
296 if (ret == 1)
297 lock_data->idle_has_lock = 1;
298 }
299 spin_unlock_bh(&lock_data->spinlock);
300 }
301 EXPORT_SYMBOL(drm_legacy_idlelock_take);
302
drm_legacy_idlelock_release(struct drm_lock_data * lock_data)303 void drm_legacy_idlelock_release(struct drm_lock_data *lock_data)
304 {
305 unsigned int old, prev;
306 volatile unsigned int *lock = &lock_data->hw_lock->lock;
307
308 spin_lock_bh(&lock_data->spinlock);
309 if (--lock_data->kernel_waiters == 0) {
310 if (lock_data->idle_has_lock) {
311 do {
312 old = *lock;
313 prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT);
314 } while (prev != old);
315 wake_up_interruptible(&lock_data->lock_queue);
316 lock_data->idle_has_lock = 0;
317 }
318 }
319 spin_unlock_bh(&lock_data->spinlock);
320 }
321 EXPORT_SYMBOL(drm_legacy_idlelock_release);
322
drm_legacy_i_have_hw_lock(struct drm_device * dev,struct drm_file * file_priv)323 static int drm_legacy_i_have_hw_lock(struct drm_device *dev,
324 struct drm_file *file_priv)
325 {
326 struct drm_master *master = file_priv->master;
327 return (file_priv->lock_count && master->lock.hw_lock &&
328 _DRM_LOCK_IS_HELD(master->lock.hw_lock->lock) &&
329 master->lock.file_priv == file_priv);
330 }
331
drm_legacy_lock_release(struct drm_device * dev,struct file * filp)332 void drm_legacy_lock_release(struct drm_device *dev, struct file *filp)
333 {
334 struct drm_file *file_priv = filp->private_data;
335
336 /* if the master has gone away we can't do anything with the lock */
337 if (!dev->master)
338 return;
339
340 if (drm_legacy_i_have_hw_lock(dev, file_priv)) {
341 DRM_DEBUG("File %p released, freeing lock for context %d\n",
342 filp, _DRM_LOCKING_CONTEXT(file_priv->master->lock.hw_lock->lock));
343 drm_legacy_lock_free(&file_priv->master->lock,
344 _DRM_LOCKING_CONTEXT(file_priv->master->lock.hw_lock->lock));
345 }
346 }
347