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 <linux/sched/signal.h>
38
39 #include <drm/drm.h>
40 #include <drm/drm_drv.h>
41 #include <drm/drm_file.h>
42 #include <drm/drm_print.h>
43
44 #include "drm_internal.h"
45 #include "drm_legacy.h"
46
47 static int drm_lock_take(struct drm_lock_data *lock_data, unsigned int context);
48
49 /*
50 * Take the heavyweight lock.
51 *
52 * \param lock lock pointer.
53 * \param context locking context.
54 * \return one if the lock is held, or zero otherwise.
55 *
56 * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
57 */
58 static
drm_lock_take(struct drm_lock_data * lock_data,unsigned int context)59 int drm_lock_take(struct drm_lock_data *lock_data,
60 unsigned int context)
61 {
62 unsigned int old, new, prev;
63 volatile unsigned int *lock = &lock_data->hw_lock->lock;
64
65 spin_lock_bh(&lock_data->spinlock);
66 do {
67 old = *lock;
68 if (old & _DRM_LOCK_HELD)
69 new = old | _DRM_LOCK_CONT;
70 else {
71 new = context | _DRM_LOCK_HELD |
72 ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
73 _DRM_LOCK_CONT : 0);
74 }
75 prev = cmpxchg(lock, old, new);
76 } while (prev != old);
77 spin_unlock_bh(&lock_data->spinlock);
78
79 if (_DRM_LOCKING_CONTEXT(old) == context) {
80 if (old & _DRM_LOCK_HELD) {
81 if (context != DRM_KERNEL_CONTEXT) {
82 DRM_ERROR("%d holds heavyweight lock\n",
83 context);
84 }
85 return 0;
86 }
87 }
88
89 if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) {
90 /* Have lock */
91 return 1;
92 }
93 return 0;
94 }
95
96 /*
97 * This takes a lock forcibly and hands it to context. Should ONLY be used
98 * inside *_unlock to give lock to kernel before calling *_dma_schedule.
99 *
100 * \param dev DRM device.
101 * \param lock lock pointer.
102 * \param context locking context.
103 * \return always one.
104 *
105 * Resets the lock file pointer.
106 * Marks the lock as held by the given context, via the \p cmpxchg instruction.
107 */
drm_lock_transfer(struct drm_lock_data * lock_data,unsigned int context)108 static int drm_lock_transfer(struct drm_lock_data *lock_data,
109 unsigned int context)
110 {
111 unsigned int old, new, prev;
112 volatile unsigned int *lock = &lock_data->hw_lock->lock;
113
114 lock_data->file_priv = NULL;
115 do {
116 old = *lock;
117 new = context | _DRM_LOCK_HELD;
118 prev = cmpxchg(lock, old, new);
119 } while (prev != old);
120 return 1;
121 }
122
drm_legacy_lock_free(struct drm_lock_data * lock_data,unsigned int context)123 static int drm_legacy_lock_free(struct drm_lock_data *lock_data,
124 unsigned int context)
125 {
126 unsigned int old, new, prev;
127 volatile unsigned int *lock = &lock_data->hw_lock->lock;
128
129 spin_lock_bh(&lock_data->spinlock);
130 if (lock_data->kernel_waiters != 0) {
131 drm_lock_transfer(lock_data, 0);
132 lock_data->idle_has_lock = 1;
133 spin_unlock_bh(&lock_data->spinlock);
134 return 1;
135 }
136 spin_unlock_bh(&lock_data->spinlock);
137
138 do {
139 old = *lock;
140 new = _DRM_LOCKING_CONTEXT(old);
141 prev = cmpxchg(lock, old, new);
142 } while (prev != old);
143
144 if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
145 DRM_ERROR("%d freed heavyweight lock held by %d\n",
146 context, _DRM_LOCKING_CONTEXT(old));
147 return 1;
148 }
149 wake_up_interruptible(&lock_data->lock_queue);
150 return 0;
151 }
152
153 /*
154 * Lock ioctl.
155 *
156 * \param inode device inode.
157 * \param file_priv DRM file private.
158 * \param cmd command.
159 * \param arg user argument, pointing to a drm_lock structure.
160 * \return zero on success or negative number on failure.
161 *
162 * Add the current task to the lock wait queue, and attempt to take to lock.
163 */
drm_legacy_lock(struct drm_device * dev,void * data,struct drm_file * file_priv)164 int drm_legacy_lock(struct drm_device *dev, void *data,
165 struct drm_file *file_priv)
166 {
167 DECLARE_WAITQUEUE(entry, current);
168 struct drm_lock *lock = data;
169 struct drm_master *master = file_priv->master;
170 int ret = 0;
171
172 if (!drm_core_check_feature(dev, DRIVER_LEGACY))
173 return -EOPNOTSUPP;
174
175 ++file_priv->lock_count;
176
177 if (lock->context == DRM_KERNEL_CONTEXT) {
178 DRM_ERROR("Process %d using kernel context %d\n",
179 task_pid_nr(current), lock->context);
180 return -EINVAL;
181 }
182
183 DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
184 lock->context, task_pid_nr(current),
185 master->lock.hw_lock ? master->lock.hw_lock->lock : -1,
186 lock->flags);
187
188 add_wait_queue(&master->lock.lock_queue, &entry);
189 spin_lock_bh(&master->lock.spinlock);
190 master->lock.user_waiters++;
191 spin_unlock_bh(&master->lock.spinlock);
192
193 for (;;) {
194 __set_current_state(TASK_INTERRUPTIBLE);
195 if (!master->lock.hw_lock) {
196 /* Device has been unregistered */
197 send_sig(SIGTERM, current, 0);
198 ret = -EINTR;
199 break;
200 }
201 if (drm_lock_take(&master->lock, lock->context)) {
202 master->lock.file_priv = file_priv;
203 master->lock.lock_time = jiffies;
204 break; /* Got lock */
205 }
206
207 /* Contention */
208 mutex_unlock(&drm_global_mutex);
209 schedule();
210 mutex_lock(&drm_global_mutex);
211 if (signal_pending(current)) {
212 ret = -EINTR;
213 break;
214 }
215 }
216 spin_lock_bh(&master->lock.spinlock);
217 master->lock.user_waiters--;
218 spin_unlock_bh(&master->lock.spinlock);
219 __set_current_state(TASK_RUNNING);
220 remove_wait_queue(&master->lock.lock_queue, &entry);
221
222 DRM_DEBUG("%d %s\n", lock->context,
223 ret ? "interrupted" : "has lock");
224 if (ret) return ret;
225
226 /* don't set the block all signals on the master process for now
227 * really probably not the correct answer but lets us debug xkb
228 * xserver for now */
229 if (!drm_is_current_master(file_priv)) {
230 dev->sigdata.context = lock->context;
231 dev->sigdata.lock = master->lock.hw_lock;
232 }
233
234 if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT))
235 {
236 if (dev->driver->dma_quiescent(dev)) {
237 DRM_DEBUG("%d waiting for DMA quiescent\n",
238 lock->context);
239 return -EBUSY;
240 }
241 }
242
243 return 0;
244 }
245
246 /*
247 * Unlock ioctl.
248 *
249 * \param inode device inode.
250 * \param file_priv DRM file private.
251 * \param cmd command.
252 * \param arg user argument, pointing to a drm_lock structure.
253 * \return zero on success or negative number on failure.
254 *
255 * Transfer and free the lock.
256 */
drm_legacy_unlock(struct drm_device * dev,void * data,struct drm_file * file_priv)257 int drm_legacy_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv)
258 {
259 struct drm_lock *lock = data;
260 struct drm_master *master = file_priv->master;
261
262 if (!drm_core_check_feature(dev, DRIVER_LEGACY))
263 return -EOPNOTSUPP;
264
265 if (lock->context == DRM_KERNEL_CONTEXT) {
266 DRM_ERROR("Process %d using kernel context %d\n",
267 task_pid_nr(current), lock->context);
268 return -EINVAL;
269 }
270
271 if (drm_legacy_lock_free(&master->lock, lock->context)) {
272 /* FIXME: Should really bail out here. */
273 }
274
275 return 0;
276 }
277
278 /*
279 * This function returns immediately and takes the hw lock
280 * with the kernel context if it is free, otherwise it gets the highest priority when and if
281 * it is eventually released.
282 *
283 * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held
284 * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause
285 * a deadlock, which is why the "idlelock" was invented).
286 *
287 * This should be sufficient to wait for GPU idle without
288 * having to worry about starvation.
289 */
drm_legacy_idlelock_take(struct drm_lock_data * lock_data)290 void drm_legacy_idlelock_take(struct drm_lock_data *lock_data)
291 {
292 int ret;
293
294 spin_lock_bh(&lock_data->spinlock);
295 lock_data->kernel_waiters++;
296 if (!lock_data->idle_has_lock) {
297
298 spin_unlock_bh(&lock_data->spinlock);
299 ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
300 spin_lock_bh(&lock_data->spinlock);
301
302 if (ret == 1)
303 lock_data->idle_has_lock = 1;
304 }
305 spin_unlock_bh(&lock_data->spinlock);
306 }
307 EXPORT_SYMBOL(drm_legacy_idlelock_take);
308
drm_legacy_idlelock_release(struct drm_lock_data * lock_data)309 void drm_legacy_idlelock_release(struct drm_lock_data *lock_data)
310 {
311 unsigned int old, prev;
312 volatile unsigned int *lock = &lock_data->hw_lock->lock;
313
314 spin_lock_bh(&lock_data->spinlock);
315 if (--lock_data->kernel_waiters == 0) {
316 if (lock_data->idle_has_lock) {
317 do {
318 old = *lock;
319 prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT);
320 } while (prev != old);
321 wake_up_interruptible(&lock_data->lock_queue);
322 lock_data->idle_has_lock = 0;
323 }
324 }
325 spin_unlock_bh(&lock_data->spinlock);
326 }
327 EXPORT_SYMBOL(drm_legacy_idlelock_release);
328
drm_legacy_i_have_hw_lock(struct drm_device * dev,struct drm_file * file_priv)329 static int drm_legacy_i_have_hw_lock(struct drm_device *dev,
330 struct drm_file *file_priv)
331 {
332 struct drm_master *master = file_priv->master;
333
334 return (file_priv->lock_count && master->lock.hw_lock &&
335 _DRM_LOCK_IS_HELD(master->lock.hw_lock->lock) &&
336 master->lock.file_priv == file_priv);
337 }
338
drm_legacy_lock_release(struct drm_device * dev,struct file * filp)339 void drm_legacy_lock_release(struct drm_device *dev, struct file *filp)
340 {
341 struct drm_file *file_priv = filp->private_data;
342
343 /* if the master has gone away we can't do anything with the lock */
344 if (!dev->master)
345 return;
346
347 if (drm_legacy_i_have_hw_lock(dev, file_priv)) {
348 DRM_DEBUG("File %p released, freeing lock for context %d\n",
349 filp, _DRM_LOCKING_CONTEXT(file_priv->master->lock.hw_lock->lock));
350 drm_legacy_lock_free(&file_priv->master->lock,
351 _DRM_LOCKING_CONTEXT(file_priv->master->lock.hw_lock->lock));
352 }
353 }
354
drm_legacy_lock_master_cleanup(struct drm_device * dev,struct drm_master * master)355 void drm_legacy_lock_master_cleanup(struct drm_device *dev, struct drm_master *master)
356 {
357 if (!drm_core_check_feature(dev, DRIVER_LEGACY))
358 return;
359
360 /*
361 * Since the master is disappearing, so is the
362 * possibility to lock.
363 */
364 mutex_lock(&dev->struct_mutex);
365 if (master->lock.hw_lock) {
366 if (dev->sigdata.lock == master->lock.hw_lock)
367 dev->sigdata.lock = NULL;
368 master->lock.hw_lock = NULL;
369 master->lock.file_priv = NULL;
370 wake_up_interruptible_all(&master->lock.lock_queue);
371 }
372 mutex_unlock(&dev->struct_mutex);
373 }
374