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51fd371b RC |
1 | /* |
2 | * Copyright (C) 2014 Red Hat | |
3 | * Author: Rob Clark <robdclark@gmail.com> | |
4 | * | |
5 | * Permission is hereby granted, free of charge, to any person obtaining a | |
6 | * copy of this software and associated documentation files (the "Software"), | |
7 | * to deal in the Software without restriction, including without limitation | |
8 | * the rights to use, copy, modify, merge, publish, distribute, sublicense, | |
9 | * and/or sell copies of the Software, and to permit persons to whom the | |
10 | * Software is furnished to do so, subject to the following conditions: | |
11 | * | |
12 | * The above copyright notice and this permission notice shall be included in | |
13 | * all copies or substantial portions of the Software. | |
14 | * | |
15 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | |
16 | * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | |
17 | * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL | |
18 | * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR | |
19 | * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, | |
20 | * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR | |
21 | * OTHER DEALINGS IN THE SOFTWARE. | |
22 | */ | |
23 | ||
24 | #include <drm/drmP.h> | |
25 | #include <drm/drm_crtc.h> | |
26 | #include <drm/drm_modeset_lock.h> | |
27 | ||
28 | /** | |
29 | * DOC: kms locking | |
30 | * | |
31 | * As KMS moves toward more fine grained locking, and atomic ioctl where | |
32 | * userspace can indirectly control locking order, it becomes necessary | |
33 | * to use ww_mutex and acquire-contexts to avoid deadlocks. But because | |
34 | * the locking is more distributed around the driver code, we want a bit | |
35 | * of extra utility/tracking out of our acquire-ctx. This is provided | |
36 | * by drm_modeset_lock / drm_modeset_acquire_ctx. | |
37 | * | |
38 | * For basic principles of ww_mutex, see: Documentation/ww-mutex-design.txt | |
39 | * | |
40 | * The basic usage pattern is to: | |
41 | * | |
42 | * drm_modeset_acquire_init(&ctx) | |
43 | * retry: | |
44 | * foreach (lock in random_ordered_set_of_locks) { | |
45 | * ret = drm_modeset_lock(lock, &ctx) | |
46 | * if (ret == -EDEADLK) { | |
47 | * drm_modeset_backoff(&ctx); | |
48 | * goto retry; | |
49 | * } | |
50 | * } | |
51 | * | |
52 | * ... do stuff ... | |
53 | * | |
54 | * drm_modeset_drop_locks(&ctx); | |
55 | * drm_modeset_acquire_fini(&ctx); | |
56 | */ | |
57 | ||
58 | ||
a6a8bb84 DV |
59 | /** |
60 | * drm_modeset_lock_all - take all modeset locks | |
61 | * @dev: drm device | |
62 | * | |
63 | * This function takes all modeset locks, suitable where a more fine-grained | |
64 | * scheme isn't (yet) implemented. Locks must be dropped with | |
65 | * drm_modeset_unlock_all. | |
66 | */ | |
67 | void drm_modeset_lock_all(struct drm_device *dev) | |
68 | { | |
69 | struct drm_mode_config *config = &dev->mode_config; | |
70 | struct drm_modeset_acquire_ctx *ctx; | |
71 | int ret; | |
72 | ||
73 | ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); | |
74 | if (WARN_ON(!ctx)) | |
75 | return; | |
76 | ||
77 | mutex_lock(&config->mutex); | |
78 | ||
79 | drm_modeset_acquire_init(ctx, 0); | |
80 | ||
81 | retry: | |
82 | ret = drm_modeset_lock(&config->connection_mutex, ctx); | |
83 | if (ret) | |
84 | goto fail; | |
85 | ret = drm_modeset_lock_all_crtcs(dev, ctx); | |
86 | if (ret) | |
87 | goto fail; | |
88 | ||
89 | WARN_ON(config->acquire_ctx); | |
90 | ||
91 | /* now we hold the locks, so now that it is safe, stash the | |
92 | * ctx for drm_modeset_unlock_all(): | |
93 | */ | |
94 | config->acquire_ctx = ctx; | |
95 | ||
96 | drm_warn_on_modeset_not_all_locked(dev); | |
97 | ||
98 | return; | |
99 | ||
100 | fail: | |
101 | if (ret == -EDEADLK) { | |
102 | drm_modeset_backoff(ctx); | |
103 | goto retry; | |
104 | } | |
105 | } | |
106 | EXPORT_SYMBOL(drm_modeset_lock_all); | |
107 | ||
108 | /** | |
109 | * drm_modeset_unlock_all - drop all modeset locks | |
110 | * @dev: device | |
111 | * | |
112 | * This function drop all modeset locks taken by drm_modeset_lock_all. | |
113 | */ | |
114 | void drm_modeset_unlock_all(struct drm_device *dev) | |
115 | { | |
116 | struct drm_mode_config *config = &dev->mode_config; | |
117 | struct drm_modeset_acquire_ctx *ctx = config->acquire_ctx; | |
118 | ||
119 | if (WARN_ON(!ctx)) | |
120 | return; | |
121 | ||
122 | config->acquire_ctx = NULL; | |
123 | drm_modeset_drop_locks(ctx); | |
124 | drm_modeset_acquire_fini(ctx); | |
125 | ||
126 | kfree(ctx); | |
127 | ||
128 | mutex_unlock(&dev->mode_config.mutex); | |
129 | } | |
130 | EXPORT_SYMBOL(drm_modeset_unlock_all); | |
131 | ||
d059f652 DV |
132 | /** |
133 | * drm_modeset_lock_crtc - lock crtc with hidden acquire ctx | |
134 | * @crtc: drm crtc | |
135 | * | |
136 | * This function locks the given crtc using a hidden acquire context. This is | |
137 | * necessary so that drivers internally using the atomic interfaces can grab | |
138 | * further locks with the lock acquire context. | |
139 | */ | |
140 | void drm_modeset_lock_crtc(struct drm_crtc *crtc) | |
141 | { | |
142 | struct drm_modeset_acquire_ctx *ctx; | |
143 | int ret; | |
144 | ||
145 | ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); | |
146 | if (WARN_ON(!ctx)) | |
147 | return; | |
148 | ||
149 | drm_modeset_acquire_init(ctx, 0); | |
150 | ||
151 | retry: | |
152 | ret = drm_modeset_lock(&crtc->mutex, ctx); | |
153 | if (ret) | |
154 | goto fail; | |
155 | ||
156 | WARN_ON(crtc->acquire_ctx); | |
157 | ||
158 | /* now we hold the locks, so now that it is safe, stash the | |
159 | * ctx for drm_modeset_unlock_crtc(): | |
160 | */ | |
161 | crtc->acquire_ctx = ctx; | |
162 | ||
163 | return; | |
164 | ||
165 | fail: | |
166 | if (ret == -EDEADLK) { | |
167 | drm_modeset_backoff(ctx); | |
168 | goto retry; | |
169 | } | |
170 | } | |
171 | EXPORT_SYMBOL(drm_modeset_lock_crtc); | |
172 | ||
173 | /** | |
174 | * drm_modeset_legacy_acquire_ctx - find acquire ctx for legacy ioctls | |
175 | * crtc: drm crtc | |
176 | * | |
177 | * Legacy ioctl operations like cursor updates or page flips only have per-crtc | |
178 | * locking, and store the acquire ctx in the corresponding crtc. All other | |
179 | * legacy operations take all locks and use a global acquire context. This | |
180 | * function grabs the right one. | |
181 | */ | |
182 | struct drm_modeset_acquire_ctx * | |
183 | drm_modeset_legacy_acquire_ctx(struct drm_crtc *crtc) | |
184 | { | |
185 | if (crtc->acquire_ctx) | |
186 | return crtc->acquire_ctx; | |
187 | ||
188 | WARN_ON(!crtc->dev->mode_config.acquire_ctx); | |
189 | ||
190 | return crtc->dev->mode_config.acquire_ctx; | |
191 | } | |
192 | EXPORT_SYMBOL(drm_modeset_legacy_acquire_ctx); | |
193 | ||
194 | /** | |
195 | * drm_modeset_unlock_crtc - drop crtc lock | |
196 | * @crtc: drm crtc | |
197 | * | |
198 | * This drops the crtc lock acquire with drm_modeset_lock_crtc() and all other | |
199 | * locks acquired through the hidden context. | |
200 | */ | |
201 | void drm_modeset_unlock_crtc(struct drm_crtc *crtc) | |
202 | { | |
203 | struct drm_modeset_acquire_ctx *ctx = crtc->acquire_ctx; | |
204 | ||
205 | if (WARN_ON(!ctx)) | |
206 | return; | |
207 | ||
208 | crtc->acquire_ctx = NULL; | |
209 | drm_modeset_drop_locks(ctx); | |
210 | drm_modeset_acquire_fini(ctx); | |
211 | ||
212 | kfree(ctx); | |
213 | } | |
214 | EXPORT_SYMBOL(drm_modeset_unlock_crtc); | |
215 | ||
a6a8bb84 DV |
216 | /** |
217 | * drm_warn_on_modeset_not_all_locked - check that all modeset locks are locked | |
218 | * @dev: device | |
219 | * | |
220 | * Useful as a debug assert. | |
221 | */ | |
222 | void drm_warn_on_modeset_not_all_locked(struct drm_device *dev) | |
223 | { | |
224 | struct drm_crtc *crtc; | |
225 | ||
226 | /* Locking is currently fubar in the panic handler. */ | |
227 | if (oops_in_progress) | |
228 | return; | |
229 | ||
230 | list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) | |
231 | WARN_ON(!drm_modeset_is_locked(&crtc->mutex)); | |
232 | ||
233 | WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex)); | |
234 | WARN_ON(!mutex_is_locked(&dev->mode_config.mutex)); | |
235 | } | |
236 | EXPORT_SYMBOL(drm_warn_on_modeset_not_all_locked); | |
237 | ||
51fd371b RC |
238 | /** |
239 | * drm_modeset_acquire_init - initialize acquire context | |
240 | * @ctx: the acquire context | |
241 | * @flags: for future | |
242 | */ | |
243 | void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx, | |
244 | uint32_t flags) | |
245 | { | |
fb54918a | 246 | memset(ctx, 0, sizeof(*ctx)); |
51fd371b RC |
247 | ww_acquire_init(&ctx->ww_ctx, &crtc_ww_class); |
248 | INIT_LIST_HEAD(&ctx->locked); | |
249 | } | |
250 | EXPORT_SYMBOL(drm_modeset_acquire_init); | |
251 | ||
252 | /** | |
253 | * drm_modeset_acquire_fini - cleanup acquire context | |
254 | * @ctx: the acquire context | |
255 | */ | |
256 | void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx) | |
257 | { | |
258 | ww_acquire_fini(&ctx->ww_ctx); | |
259 | } | |
260 | EXPORT_SYMBOL(drm_modeset_acquire_fini); | |
261 | ||
262 | /** | |
263 | * drm_modeset_drop_locks - drop all locks | |
264 | * @ctx: the acquire context | |
265 | * | |
266 | * Drop all locks currently held against this acquire context. | |
267 | */ | |
268 | void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx *ctx) | |
269 | { | |
270 | WARN_ON(ctx->contended); | |
271 | while (!list_empty(&ctx->locked)) { | |
272 | struct drm_modeset_lock *lock; | |
273 | ||
274 | lock = list_first_entry(&ctx->locked, | |
275 | struct drm_modeset_lock, head); | |
276 | ||
277 | drm_modeset_unlock(lock); | |
278 | } | |
279 | } | |
280 | EXPORT_SYMBOL(drm_modeset_drop_locks); | |
281 | ||
282 | static inline int modeset_lock(struct drm_modeset_lock *lock, | |
283 | struct drm_modeset_acquire_ctx *ctx, | |
284 | bool interruptible, bool slow) | |
285 | { | |
286 | int ret; | |
287 | ||
288 | WARN_ON(ctx->contended); | |
289 | ||
290 | if (interruptible && slow) { | |
291 | ret = ww_mutex_lock_slow_interruptible(&lock->mutex, &ctx->ww_ctx); | |
292 | } else if (interruptible) { | |
293 | ret = ww_mutex_lock_interruptible(&lock->mutex, &ctx->ww_ctx); | |
294 | } else if (slow) { | |
295 | ww_mutex_lock_slow(&lock->mutex, &ctx->ww_ctx); | |
296 | ret = 0; | |
297 | } else { | |
298 | ret = ww_mutex_lock(&lock->mutex, &ctx->ww_ctx); | |
299 | } | |
300 | if (!ret) { | |
301 | WARN_ON(!list_empty(&lock->head)); | |
302 | list_add(&lock->head, &ctx->locked); | |
303 | } else if (ret == -EALREADY) { | |
304 | /* we already hold the lock.. this is fine. For atomic | |
305 | * we will need to be able to drm_modeset_lock() things | |
306 | * without having to keep track of what is already locked | |
307 | * or not. | |
308 | */ | |
309 | ret = 0; | |
310 | } else if (ret == -EDEADLK) { | |
311 | ctx->contended = lock; | |
312 | } | |
313 | ||
314 | return ret; | |
315 | } | |
316 | ||
317 | static int modeset_backoff(struct drm_modeset_acquire_ctx *ctx, | |
318 | bool interruptible) | |
319 | { | |
320 | struct drm_modeset_lock *contended = ctx->contended; | |
321 | ||
322 | ctx->contended = NULL; | |
323 | ||
324 | if (WARN_ON(!contended)) | |
325 | return 0; | |
326 | ||
327 | drm_modeset_drop_locks(ctx); | |
328 | ||
329 | return modeset_lock(contended, ctx, interruptible, true); | |
330 | } | |
331 | ||
332 | /** | |
333 | * drm_modeset_backoff - deadlock avoidance backoff | |
334 | * @ctx: the acquire context | |
335 | * | |
336 | * If deadlock is detected (ie. drm_modeset_lock() returns -EDEADLK), | |
337 | * you must call this function to drop all currently held locks and | |
338 | * block until the contended lock becomes available. | |
339 | */ | |
340 | void drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx) | |
341 | { | |
342 | modeset_backoff(ctx, false); | |
343 | } | |
344 | EXPORT_SYMBOL(drm_modeset_backoff); | |
345 | ||
346 | /** | |
347 | * drm_modeset_backoff_interruptible - deadlock avoidance backoff | |
348 | * @ctx: the acquire context | |
349 | * | |
350 | * Interruptible version of drm_modeset_backoff() | |
351 | */ | |
352 | int drm_modeset_backoff_interruptible(struct drm_modeset_acquire_ctx *ctx) | |
353 | { | |
354 | return modeset_backoff(ctx, true); | |
355 | } | |
356 | EXPORT_SYMBOL(drm_modeset_backoff_interruptible); | |
357 | ||
358 | /** | |
359 | * drm_modeset_lock - take modeset lock | |
360 | * @lock: lock to take | |
361 | * @ctx: acquire ctx | |
362 | * | |
363 | * If ctx is not NULL, then its ww acquire context is used and the | |
364 | * lock will be tracked by the context and can be released by calling | |
365 | * drm_modeset_drop_locks(). If -EDEADLK is returned, this means a | |
366 | * deadlock scenario has been detected and it is an error to attempt | |
367 | * to take any more locks without first calling drm_modeset_backoff(). | |
368 | */ | |
369 | int drm_modeset_lock(struct drm_modeset_lock *lock, | |
370 | struct drm_modeset_acquire_ctx *ctx) | |
371 | { | |
372 | if (ctx) | |
373 | return modeset_lock(lock, ctx, false, false); | |
374 | ||
375 | ww_mutex_lock(&lock->mutex, NULL); | |
376 | return 0; | |
377 | } | |
378 | EXPORT_SYMBOL(drm_modeset_lock); | |
379 | ||
380 | /** | |
381 | * drm_modeset_lock_interruptible - take modeset lock | |
382 | * @lock: lock to take | |
383 | * @ctx: acquire ctx | |
384 | * | |
385 | * Interruptible version of drm_modeset_lock() | |
386 | */ | |
387 | int drm_modeset_lock_interruptible(struct drm_modeset_lock *lock, | |
388 | struct drm_modeset_acquire_ctx *ctx) | |
389 | { | |
390 | if (ctx) | |
391 | return modeset_lock(lock, ctx, true, false); | |
392 | ||
393 | return ww_mutex_lock_interruptible(&lock->mutex, NULL); | |
394 | } | |
395 | EXPORT_SYMBOL(drm_modeset_lock_interruptible); | |
396 | ||
397 | /** | |
398 | * drm_modeset_unlock - drop modeset lock | |
399 | * @lock: lock to release | |
400 | */ | |
401 | void drm_modeset_unlock(struct drm_modeset_lock *lock) | |
402 | { | |
403 | list_del_init(&lock->head); | |
404 | ww_mutex_unlock(&lock->mutex); | |
405 | } | |
406 | EXPORT_SYMBOL(drm_modeset_unlock); | |
407 | ||
408 | /* Temporary.. until we have sufficiently fine grained locking, there | |
409 | * are a couple scenarios where it is convenient to grab all crtc locks. | |
410 | * It is planned to remove this: | |
411 | */ | |
412 | int drm_modeset_lock_all_crtcs(struct drm_device *dev, | |
413 | struct drm_modeset_acquire_ctx *ctx) | |
414 | { | |
415 | struct drm_mode_config *config = &dev->mode_config; | |
416 | struct drm_crtc *crtc; | |
417 | int ret = 0; | |
418 | ||
419 | list_for_each_entry(crtc, &config->crtc_list, head) { | |
420 | ret = drm_modeset_lock(&crtc->mutex, ctx); | |
421 | if (ret) | |
422 | return ret; | |
423 | } | |
424 | ||
425 | return 0; | |
426 | } | |
427 | EXPORT_SYMBOL(drm_modeset_lock_all_crtcs); |