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/drmP.h>
40 #include "drm_legacy.h"
41 #include "drm_internal.h"
42
43 #if 0
44 static int drm_lock_take(struct drm_lock_data *lock_data, unsigned int context);
45
46 /**
47 * Take the heavyweight lock.
48 *
49 * \param lock lock pointer.
50 * \param context locking context.
51 * \return one if the lock is held, or zero otherwise.
52 *
53 * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
54 */
55 static
56 int drm_lock_take(struct drm_lock_data *lock_data,
57 unsigned int context)
58 {
59 unsigned int old, new, prev;
60 volatile unsigned int *lock = &lock_data->hw_lock->lock;
61
62 spin_lock_bh(&lock_data->spinlock);
63 do {
64 old = *lock;
65 if (old & _DRM_LOCK_HELD)
66 new = old | _DRM_LOCK_CONT;
67 else {
68 new = context | _DRM_LOCK_HELD |
69 ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
70 _DRM_LOCK_CONT : 0);
71 }
72 prev = cmpxchg(lock, old, new);
73 } while (prev != old);
74 spin_unlock_bh(&lock_data->spinlock);
75
76 if (_DRM_LOCKING_CONTEXT(old) == context) {
77 if (old & _DRM_LOCK_HELD) {
78 if (context != DRM_KERNEL_CONTEXT) {
79 DRM_ERROR("%d holds heavyweight lock\n",
80 context);
81 }
82 return 0;
83 }
84 }
85
86 if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) {
87 /* Have lock */
88 return 1;
89 }
90 return 0;
91 }
92
93 /**
94 * This takes a lock forcibly and hands it to context. Should ONLY be used
95 * inside *_unlock to give lock to kernel before calling *_dma_schedule.
96 *
97 * \param dev DRM device.
98 * \param lock lock pointer.
99 * \param context locking context.
100 * \return always one.
101 *
102 * Resets the lock file pointer.
103 * Marks the lock as held by the given context, via the \p cmpxchg instruction.
104 */
105 static int drm_lock_transfer(struct drm_lock_data *lock_data,
106 unsigned int context)
107 {
108 unsigned int old, new, prev;
109 volatile unsigned int *lock = &lock_data->hw_lock->lock;
110
111 lock_data->file_priv = NULL;
112 do {
113 old = *lock;
114 new = context | _DRM_LOCK_HELD;
115 prev = cmpxchg(lock, old, new);
116 } while (prev != old);
117 return 1;
118 }
119
120 static int drm_legacy_lock_free(struct drm_lock_data *lock_data,
121 unsigned int context)
122 {
123 unsigned int old, new, prev;
124 volatile unsigned int *lock = &lock_data->hw_lock->lock;
125
126 spin_lock_bh(&lock_data->spinlock);
127 if (lock_data->kernel_waiters != 0) {
128 drm_lock_transfer(lock_data, 0);
129 lock_data->idle_has_lock = 1;
130 spin_unlock_bh(&lock_data->spinlock);
131 return 1;
132 }
133 spin_unlock_bh(&lock_data->spinlock);
134
135 do {
136 old = *lock;
137 new = _DRM_LOCKING_CONTEXT(old);
138 prev = cmpxchg(lock, old, new);
139 } while (prev != old);
140
141 if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
142 DRM_ERROR("%d freed heavyweight lock held by %d\n",
143 context, _DRM_LOCKING_CONTEXT(old));
144 return 1;
145 }
146 wake_up_interruptible(&lock_data->lock_queue);
147 return 0;
148 }
149 #endif
150
151 /**
152 * Lock ioctl.
153 *
154 * \param inode device inode.
155 * \param file_priv DRM file private.
156 * \param cmd command.
157 * \param arg user argument, pointing to a drm_lock structure.
158 * \return zero on success or negative number on failure.
159 *
160 * Add the current task to the lock wait queue, and attempt to take to lock.
161 */
drm_legacy_lock(struct drm_device * dev,void * data,struct drm_file * file_priv)162 int drm_legacy_lock(struct drm_device *dev, void *data,
163 struct drm_file *file_priv)
164 {
165 #if 0
166 DECLARE_WAITQUEUE(entry, current);
167 struct drm_lock *lock = data;
168 struct drm_master *master = file_priv->master;
169 int ret = 0;
170
171 if (!drm_core_check_feature(dev, DRIVER_LEGACY))
172 return -EINVAL;
173
174 ++file_priv->lock_count;
175
176 if (lock->context == DRM_KERNEL_CONTEXT) {
177 DRM_ERROR("Process %d using kernel context %d\n",
178 task_pid_nr(current), lock->context);
179 return -EINVAL;
180 }
181
182 DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
183 lock->context, task_pid_nr(current),
184 master->lock.hw_lock ? master->lock.hw_lock->lock : -1,
185 lock->flags);
186
187 add_wait_queue(&master->lock.lock_queue, &entry);
188 spin_lock_bh(&master->lock.spinlock);
189 master->lock.user_waiters++;
190 spin_unlock_bh(&master->lock.spinlock);
191
192 for (;;) {
193 __set_current_state(TASK_INTERRUPTIBLE);
194 if (!master->lock.hw_lock) {
195 /* Device has been unregistered */
196 send_sig(SIGTERM, current, 0);
197 ret = -EINTR;
198 break;
199 }
200 if (drm_lock_take(&master->lock, lock->context)) {
201 master->lock.file_priv = file_priv;
202 master->lock.lock_time = jiffies;
203 break; /* Got lock */
204 }
205
206 /* Contention */
207 mutex_unlock(&drm_global_mutex);
208 schedule();
209 mutex_lock(&drm_global_mutex);
210 if (signal_pending(current)) {
211 ret = -EINTR;
212 break;
213 }
214 }
215 spin_lock_bh(&master->lock.spinlock);
216 master->lock.user_waiters--;
217 spin_unlock_bh(&master->lock.spinlock);
218 __set_current_state(TASK_RUNNING);
219 remove_wait_queue(&master->lock.lock_queue, &entry);
220
221 DRM_DEBUG("%d %s\n", lock->context,
222 ret ? "interrupted" : "has lock");
223 if (ret) return ret;
224
225 /* don't set the block all signals on the master process for now
226 * really probably not the correct answer but lets us debug xkb
227 * xserver for now */
228 if (!drm_is_current_master(file_priv)) {
229 dev->sigdata.context = lock->context;
230 dev->sigdata.lock = master->lock.hw_lock;
231 }
232
233 if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT))
234 {
235 if (dev->driver->dma_quiescent(dev)) {
236 DRM_DEBUG("%d waiting for DMA quiescent\n",
237 lock->context);
238 return -EBUSY;
239 }
240 }
241 #endif
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 #if 0
260 struct drm_lock *lock = data;
261 struct drm_master *master = file_priv->master;
262
263 if (!drm_core_check_feature(dev, DRIVER_LEGACY))
264 return -EINVAL;
265
266 if (lock->context == DRM_KERNEL_CONTEXT) {
267 DRM_ERROR("Process %d using kernel context %d\n",
268 task_pid_nr(current), lock->context);
269 return -EINVAL;
270 }
271
272 if (drm_legacy_lock_free(&master->lock, lock->context)) {
273 /* FIXME: Should really bail out here. */
274 }
275 #endif
276
277 return 0;
278 }
279
280 #if 0
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
294 void 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 }
311 EXPORT_SYMBOL(drm_legacy_idlelock_take);
312
313 void 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 }
331 EXPORT_SYMBOL(drm_legacy_idlelock_release);
332
333 static int 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 #endif
342
drm_legacy_lock_release(struct drm_device * dev,struct file * filp)343 void drm_legacy_lock_release(struct drm_device *dev, struct file *filp)
344 {
345 #if 0
346 struct drm_file *file_priv = filp->private_data;
347
348 /* if the master has gone away we can't do anything with the lock */
349 if (!dev->master)
350 return;
351
352 if (drm_legacy_i_have_hw_lock(dev, file_priv)) {
353 DRM_DEBUG("File %p released, freeing lock for context %d\n",
354 filp, _DRM_LOCKING_CONTEXT(file_priv->master->lock.hw_lock->lock));
355 drm_legacy_lock_free(&file_priv->master->lock,
356 _DRM_LOCKING_CONTEXT(file_priv->master->lock.hw_lock->lock));
357 }
358 #endif
359 }
360