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 |
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: &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: &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 | */ |
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 | |
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: &lock_data->spinlock); |
130 | if (lock_data->kernel_waiters != 0) { |
131 | drm_lock_transfer(lock_data, context: 0); |
132 | lock_data->idle_has_lock = 1; |
133 | spin_unlock_bh(lock: &lock_data->spinlock); |
134 | return 1; |
135 | } |
136 | spin_unlock_bh(lock: &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 | */ |
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, feature: 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(wq_head: &master->lock.lock_queue, wq_entry: &entry); |
189 | spin_lock_bh(lock: &master->lock.spinlock); |
190 | master->lock.user_waiters++; |
191 | spin_unlock_bh(lock: &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(lock_data: &master->lock, context: 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(lock: &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(lock: &master->lock.spinlock); |
217 | master->lock.user_waiters--; |
218 | spin_unlock_bh(lock: &master->lock.spinlock); |
219 | __set_current_state(TASK_RUNNING); |
220 | remove_wait_queue(wq_head: &master->lock.lock_queue, wq_entry: &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(fpriv: 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 | */ |
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, feature: 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(lock_data: &master->lock, context: 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 | */ |
290 | void drm_legacy_idlelock_take(struct drm_lock_data *lock_data) |
291 | { |
292 | int ret; |
293 | |
294 | spin_lock_bh(lock: &lock_data->spinlock); |
295 | lock_data->kernel_waiters++; |
296 | if (!lock_data->idle_has_lock) { |
297 | |
298 | spin_unlock_bh(lock: &lock_data->spinlock); |
299 | ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT); |
300 | spin_lock_bh(lock: &lock_data->spinlock); |
301 | |
302 | if (ret == 1) |
303 | lock_data->idle_has_lock = 1; |
304 | } |
305 | spin_unlock_bh(lock: &lock_data->spinlock); |
306 | } |
307 | EXPORT_SYMBOL(drm_legacy_idlelock_take); |
308 | |
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: &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: &lock_data->spinlock); |
326 | } |
327 | EXPORT_SYMBOL(drm_legacy_idlelock_release); |
328 | |
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 | |
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(lock_data: &file_priv->master->lock, |
351 | _DRM_LOCKING_CONTEXT(file_priv->master->lock.hw_lock->lock)); |
352 | } |
353 | } |
354 | |
355 | void drm_legacy_lock_master_cleanup(struct drm_device *dev, struct drm_master *master) |
356 | { |
357 | if (!drm_core_check_feature(dev, feature: 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(lock: &dev->struct_mutex); |
373 | } |
374 | |