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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 | * | |
214e0aed | 38 | * For basic principles of ww_mutex, see: Documentation/locking/ww-mutex-design.txt |
51fd371b RC |
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 | ||
a6a8bb84 | 58 | /** |
bf9e37ba DV |
59 | * drm_modeset_lock_all - take all modeset locks |
60 | * @dev: drm device | |
cb597bb3 | 61 | * |
bf9e37ba DV |
62 | * This function takes all modeset locks, suitable where a more fine-grained |
63 | * scheme isn't (yet) implemented. Locks must be dropped with | |
64 | * drm_modeset_unlock_all. | |
a6a8bb84 | 65 | */ |
bf9e37ba | 66 | void drm_modeset_lock_all(struct drm_device *dev) |
a6a8bb84 DV |
67 | { |
68 | struct drm_mode_config *config = &dev->mode_config; | |
69 | struct drm_modeset_acquire_ctx *ctx; | |
70 | int ret; | |
71 | ||
bf9e37ba DV |
72 | ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); |
73 | if (WARN_ON(!ctx)) | |
74 | return; | |
75 | ||
76 | mutex_lock(&config->mutex); | |
a6a8bb84 DV |
77 | |
78 | drm_modeset_acquire_init(ctx, 0); | |
79 | ||
80 | retry: | |
81 | ret = drm_modeset_lock(&config->connection_mutex, ctx); | |
82 | if (ret) | |
83 | goto fail; | |
84 | ret = drm_modeset_lock_all_crtcs(dev, ctx); | |
85 | if (ret) | |
86 | goto fail; | |
87 | ||
88 | WARN_ON(config->acquire_ctx); | |
89 | ||
90 | /* now we hold the locks, so now that it is safe, stash the | |
91 | * ctx for drm_modeset_unlock_all(): | |
92 | */ | |
93 | config->acquire_ctx = ctx; | |
94 | ||
95 | drm_warn_on_modeset_not_all_locked(dev); | |
96 | ||
bf9e37ba | 97 | return; |
a6a8bb84 DV |
98 | |
99 | fail: | |
100 | if (ret == -EDEADLK) { | |
101 | drm_modeset_backoff(ctx); | |
102 | goto retry; | |
103 | } | |
cb597bb3 | 104 | |
ed181703 | 105 | kfree(ctx); |
a6a8bb84 DV |
106 | } |
107 | EXPORT_SYMBOL(drm_modeset_lock_all); | |
108 | ||
109 | /** | |
110 | * drm_modeset_unlock_all - drop all modeset locks | |
111 | * @dev: device | |
112 | * | |
113 | * This function drop all modeset locks taken by drm_modeset_lock_all. | |
114 | */ | |
115 | void drm_modeset_unlock_all(struct drm_device *dev) | |
116 | { | |
117 | struct drm_mode_config *config = &dev->mode_config; | |
118 | struct drm_modeset_acquire_ctx *ctx = config->acquire_ctx; | |
119 | ||
120 | if (WARN_ON(!ctx)) | |
121 | return; | |
122 | ||
123 | config->acquire_ctx = NULL; | |
124 | drm_modeset_drop_locks(ctx); | |
125 | drm_modeset_acquire_fini(ctx); | |
126 | ||
127 | kfree(ctx); | |
128 | ||
129 | mutex_unlock(&dev->mode_config.mutex); | |
130 | } | |
131 | EXPORT_SYMBOL(drm_modeset_unlock_all); | |
132 | ||
d059f652 | 133 | /** |
4d02e2de DV |
134 | * drm_modeset_lock_crtc - lock crtc with hidden acquire ctx for a plane update |
135 | * @crtc: DRM CRTC | |
136 | * @plane: DRM plane to be updated on @crtc | |
137 | * | |
138 | * This function locks the given crtc and plane (which should be either the | |
139 | * primary or cursor plane) using a hidden acquire context. This is necessary so | |
140 | * that drivers internally using the atomic interfaces can grab further locks | |
141 | * with the lock acquire context. | |
d059f652 | 142 | * |
4d02e2de DV |
143 | * Note that @plane can be NULL, e.g. when the cursor support hasn't yet been |
144 | * converted to universal planes yet. | |
d059f652 | 145 | */ |
4d02e2de DV |
146 | void drm_modeset_lock_crtc(struct drm_crtc *crtc, |
147 | struct drm_plane *plane) | |
d059f652 DV |
148 | { |
149 | struct drm_modeset_acquire_ctx *ctx; | |
150 | int ret; | |
151 | ||
152 | ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); | |
153 | if (WARN_ON(!ctx)) | |
154 | return; | |
155 | ||
156 | drm_modeset_acquire_init(ctx, 0); | |
157 | ||
158 | retry: | |
159 | ret = drm_modeset_lock(&crtc->mutex, ctx); | |
160 | if (ret) | |
161 | goto fail; | |
162 | ||
4d02e2de DV |
163 | if (plane) { |
164 | ret = drm_modeset_lock(&plane->mutex, ctx); | |
165 | if (ret) | |
166 | goto fail; | |
167 | ||
168 | if (plane->crtc) { | |
169 | ret = drm_modeset_lock(&plane->crtc->mutex, ctx); | |
170 | if (ret) | |
171 | goto fail; | |
172 | } | |
173 | } | |
174 | ||
d059f652 DV |
175 | WARN_ON(crtc->acquire_ctx); |
176 | ||
177 | /* now we hold the locks, so now that it is safe, stash the | |
178 | * ctx for drm_modeset_unlock_crtc(): | |
179 | */ | |
180 | crtc->acquire_ctx = ctx; | |
181 | ||
182 | return; | |
183 | ||
184 | fail: | |
185 | if (ret == -EDEADLK) { | |
186 | drm_modeset_backoff(ctx); | |
187 | goto retry; | |
188 | } | |
189 | } | |
190 | EXPORT_SYMBOL(drm_modeset_lock_crtc); | |
191 | ||
192 | /** | |
193 | * drm_modeset_legacy_acquire_ctx - find acquire ctx for legacy ioctls | |
295ee853 | 194 | * @crtc: drm crtc |
d059f652 DV |
195 | * |
196 | * Legacy ioctl operations like cursor updates or page flips only have per-crtc | |
197 | * locking, and store the acquire ctx in the corresponding crtc. All other | |
198 | * legacy operations take all locks and use a global acquire context. This | |
199 | * function grabs the right one. | |
200 | */ | |
201 | struct drm_modeset_acquire_ctx * | |
202 | drm_modeset_legacy_acquire_ctx(struct drm_crtc *crtc) | |
203 | { | |
204 | if (crtc->acquire_ctx) | |
205 | return crtc->acquire_ctx; | |
206 | ||
207 | WARN_ON(!crtc->dev->mode_config.acquire_ctx); | |
208 | ||
209 | return crtc->dev->mode_config.acquire_ctx; | |
210 | } | |
211 | EXPORT_SYMBOL(drm_modeset_legacy_acquire_ctx); | |
212 | ||
213 | /** | |
214 | * drm_modeset_unlock_crtc - drop crtc lock | |
215 | * @crtc: drm crtc | |
216 | * | |
217 | * This drops the crtc lock acquire with drm_modeset_lock_crtc() and all other | |
218 | * locks acquired through the hidden context. | |
219 | */ | |
220 | void drm_modeset_unlock_crtc(struct drm_crtc *crtc) | |
221 | { | |
222 | struct drm_modeset_acquire_ctx *ctx = crtc->acquire_ctx; | |
223 | ||
224 | if (WARN_ON(!ctx)) | |
225 | return; | |
226 | ||
227 | crtc->acquire_ctx = NULL; | |
228 | drm_modeset_drop_locks(ctx); | |
229 | drm_modeset_acquire_fini(ctx); | |
230 | ||
231 | kfree(ctx); | |
232 | } | |
233 | EXPORT_SYMBOL(drm_modeset_unlock_crtc); | |
234 | ||
a6a8bb84 DV |
235 | /** |
236 | * drm_warn_on_modeset_not_all_locked - check that all modeset locks are locked | |
237 | * @dev: device | |
238 | * | |
239 | * Useful as a debug assert. | |
240 | */ | |
241 | void drm_warn_on_modeset_not_all_locked(struct drm_device *dev) | |
242 | { | |
243 | struct drm_crtc *crtc; | |
244 | ||
245 | /* Locking is currently fubar in the panic handler. */ | |
246 | if (oops_in_progress) | |
247 | return; | |
248 | ||
e4f62546 | 249 | drm_for_each_crtc(crtc, dev) |
a6a8bb84 DV |
250 | WARN_ON(!drm_modeset_is_locked(&crtc->mutex)); |
251 | ||
252 | WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex)); | |
253 | WARN_ON(!mutex_is_locked(&dev->mode_config.mutex)); | |
254 | } | |
255 | EXPORT_SYMBOL(drm_warn_on_modeset_not_all_locked); | |
256 | ||
51fd371b RC |
257 | /** |
258 | * drm_modeset_acquire_init - initialize acquire context | |
259 | * @ctx: the acquire context | |
260 | * @flags: for future | |
261 | */ | |
262 | void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx, | |
263 | uint32_t flags) | |
264 | { | |
fb54918a | 265 | memset(ctx, 0, sizeof(*ctx)); |
51fd371b RC |
266 | ww_acquire_init(&ctx->ww_ctx, &crtc_ww_class); |
267 | INIT_LIST_HEAD(&ctx->locked); | |
268 | } | |
269 | EXPORT_SYMBOL(drm_modeset_acquire_init); | |
270 | ||
271 | /** | |
272 | * drm_modeset_acquire_fini - cleanup acquire context | |
273 | * @ctx: the acquire context | |
274 | */ | |
275 | void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx) | |
276 | { | |
277 | ww_acquire_fini(&ctx->ww_ctx); | |
278 | } | |
279 | EXPORT_SYMBOL(drm_modeset_acquire_fini); | |
280 | ||
281 | /** | |
282 | * drm_modeset_drop_locks - drop all locks | |
283 | * @ctx: the acquire context | |
284 | * | |
285 | * Drop all locks currently held against this acquire context. | |
286 | */ | |
287 | void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx *ctx) | |
288 | { | |
289 | WARN_ON(ctx->contended); | |
290 | while (!list_empty(&ctx->locked)) { | |
291 | struct drm_modeset_lock *lock; | |
292 | ||
293 | lock = list_first_entry(&ctx->locked, | |
294 | struct drm_modeset_lock, head); | |
295 | ||
296 | drm_modeset_unlock(lock); | |
297 | } | |
298 | } | |
299 | EXPORT_SYMBOL(drm_modeset_drop_locks); | |
300 | ||
301 | static inline int modeset_lock(struct drm_modeset_lock *lock, | |
302 | struct drm_modeset_acquire_ctx *ctx, | |
303 | bool interruptible, bool slow) | |
304 | { | |
305 | int ret; | |
306 | ||
307 | WARN_ON(ctx->contended); | |
308 | ||
cb597bb3 DV |
309 | if (ctx->trylock_only) { |
310 | if (!ww_mutex_trylock(&lock->mutex)) | |
311 | return -EBUSY; | |
312 | else | |
313 | return 0; | |
314 | } else if (interruptible && slow) { | |
51fd371b RC |
315 | ret = ww_mutex_lock_slow_interruptible(&lock->mutex, &ctx->ww_ctx); |
316 | } else if (interruptible) { | |
317 | ret = ww_mutex_lock_interruptible(&lock->mutex, &ctx->ww_ctx); | |
318 | } else if (slow) { | |
319 | ww_mutex_lock_slow(&lock->mutex, &ctx->ww_ctx); | |
320 | ret = 0; | |
321 | } else { | |
322 | ret = ww_mutex_lock(&lock->mutex, &ctx->ww_ctx); | |
323 | } | |
324 | if (!ret) { | |
325 | WARN_ON(!list_empty(&lock->head)); | |
326 | list_add(&lock->head, &ctx->locked); | |
327 | } else if (ret == -EALREADY) { | |
328 | /* we already hold the lock.. this is fine. For atomic | |
329 | * we will need to be able to drm_modeset_lock() things | |
330 | * without having to keep track of what is already locked | |
331 | * or not. | |
332 | */ | |
333 | ret = 0; | |
334 | } else if (ret == -EDEADLK) { | |
335 | ctx->contended = lock; | |
336 | } | |
337 | ||
338 | return ret; | |
339 | } | |
340 | ||
341 | static int modeset_backoff(struct drm_modeset_acquire_ctx *ctx, | |
342 | bool interruptible) | |
343 | { | |
344 | struct drm_modeset_lock *contended = ctx->contended; | |
345 | ||
346 | ctx->contended = NULL; | |
347 | ||
348 | if (WARN_ON(!contended)) | |
349 | return 0; | |
350 | ||
351 | drm_modeset_drop_locks(ctx); | |
352 | ||
353 | return modeset_lock(contended, ctx, interruptible, true); | |
354 | } | |
355 | ||
356 | /** | |
357 | * drm_modeset_backoff - deadlock avoidance backoff | |
358 | * @ctx: the acquire context | |
359 | * | |
360 | * If deadlock is detected (ie. drm_modeset_lock() returns -EDEADLK), | |
361 | * you must call this function to drop all currently held locks and | |
362 | * block until the contended lock becomes available. | |
363 | */ | |
364 | void drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx) | |
365 | { | |
366 | modeset_backoff(ctx, false); | |
367 | } | |
368 | EXPORT_SYMBOL(drm_modeset_backoff); | |
369 | ||
370 | /** | |
371 | * drm_modeset_backoff_interruptible - deadlock avoidance backoff | |
372 | * @ctx: the acquire context | |
373 | * | |
374 | * Interruptible version of drm_modeset_backoff() | |
375 | */ | |
376 | int drm_modeset_backoff_interruptible(struct drm_modeset_acquire_ctx *ctx) | |
377 | { | |
378 | return modeset_backoff(ctx, true); | |
379 | } | |
380 | EXPORT_SYMBOL(drm_modeset_backoff_interruptible); | |
381 | ||
382 | /** | |
383 | * drm_modeset_lock - take modeset lock | |
384 | * @lock: lock to take | |
385 | * @ctx: acquire ctx | |
386 | * | |
387 | * If ctx is not NULL, then its ww acquire context is used and the | |
388 | * lock will be tracked by the context and can be released by calling | |
389 | * drm_modeset_drop_locks(). If -EDEADLK is returned, this means a | |
390 | * deadlock scenario has been detected and it is an error to attempt | |
391 | * to take any more locks without first calling drm_modeset_backoff(). | |
392 | */ | |
393 | int drm_modeset_lock(struct drm_modeset_lock *lock, | |
394 | struct drm_modeset_acquire_ctx *ctx) | |
395 | { | |
396 | if (ctx) | |
397 | return modeset_lock(lock, ctx, false, false); | |
398 | ||
399 | ww_mutex_lock(&lock->mutex, NULL); | |
400 | return 0; | |
401 | } | |
402 | EXPORT_SYMBOL(drm_modeset_lock); | |
403 | ||
404 | /** | |
405 | * drm_modeset_lock_interruptible - take modeset lock | |
406 | * @lock: lock to take | |
407 | * @ctx: acquire ctx | |
408 | * | |
409 | * Interruptible version of drm_modeset_lock() | |
410 | */ | |
411 | int drm_modeset_lock_interruptible(struct drm_modeset_lock *lock, | |
412 | struct drm_modeset_acquire_ctx *ctx) | |
413 | { | |
414 | if (ctx) | |
415 | return modeset_lock(lock, ctx, true, false); | |
416 | ||
417 | return ww_mutex_lock_interruptible(&lock->mutex, NULL); | |
418 | } | |
419 | EXPORT_SYMBOL(drm_modeset_lock_interruptible); | |
420 | ||
421 | /** | |
422 | * drm_modeset_unlock - drop modeset lock | |
423 | * @lock: lock to release | |
424 | */ | |
425 | void drm_modeset_unlock(struct drm_modeset_lock *lock) | |
426 | { | |
427 | list_del_init(&lock->head); | |
428 | ww_mutex_unlock(&lock->mutex); | |
429 | } | |
430 | EXPORT_SYMBOL(drm_modeset_unlock); | |
431 | ||
4d02e2de DV |
432 | /* In some legacy codepaths it's convenient to just grab all the crtc and plane |
433 | * related locks. */ | |
51fd371b RC |
434 | int drm_modeset_lock_all_crtcs(struct drm_device *dev, |
435 | struct drm_modeset_acquire_ctx *ctx) | |
436 | { | |
51fd371b | 437 | struct drm_crtc *crtc; |
4d02e2de | 438 | struct drm_plane *plane; |
51fd371b RC |
439 | int ret = 0; |
440 | ||
e4f62546 | 441 | drm_for_each_crtc(crtc, dev) { |
51fd371b RC |
442 | ret = drm_modeset_lock(&crtc->mutex, ctx); |
443 | if (ret) | |
444 | return ret; | |
445 | } | |
446 | ||
e4f62546 | 447 | drm_for_each_plane(plane, dev) { |
4d02e2de DV |
448 | ret = drm_modeset_lock(&plane->mutex, ctx); |
449 | if (ret) | |
450 | return ret; | |
451 | } | |
452 | ||
51fd371b RC |
453 | return 0; |
454 | } | |
455 | EXPORT_SYMBOL(drm_modeset_lock_all_crtcs); |