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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) | |
f03d8ede | 43 | * retry: |
51fd371b | 44 | * foreach (lock in random_ordered_set_of_locks) { |
f03d8ede DCLP |
45 | * ret = drm_modeset_lock(lock, &ctx) |
46 | * if (ret == -EDEADLK) { | |
47 | * drm_modeset_backoff(&ctx); | |
48 | * goto retry; | |
49 | * } | |
51fd371b | 50 | * } |
51fd371b | 51 | * ... do stuff ... |
51fd371b RC |
52 | * drm_modeset_drop_locks(&ctx); |
53 | * drm_modeset_acquire_fini(&ctx); | |
54 | */ | |
55 | ||
a6a8bb84 | 56 | /** |
bf9e37ba | 57 | * drm_modeset_lock_all - take all modeset locks |
06eaae46 | 58 | * @dev: DRM device |
cb597bb3 | 59 | * |
bf9e37ba | 60 | * This function takes all modeset locks, suitable where a more fine-grained |
06eaae46 TR |
61 | * scheme isn't (yet) implemented. Locks must be dropped by calling the |
62 | * drm_modeset_unlock_all() function. | |
63 | * | |
64 | * This function is deprecated. It allocates a lock acquisition context and | |
65 | * stores it in the DRM device's ->mode_config. This facilitate conversion of | |
66 | * existing code because it removes the need to manually deal with the | |
67 | * acquisition context, but it is also brittle because the context is global | |
68 | * and care must be taken not to nest calls. New code should use the | |
69 | * drm_modeset_lock_all_ctx() function and pass in the context explicitly. | |
a6a8bb84 | 70 | */ |
bf9e37ba | 71 | void drm_modeset_lock_all(struct drm_device *dev) |
a6a8bb84 DV |
72 | { |
73 | struct drm_mode_config *config = &dev->mode_config; | |
74 | struct drm_modeset_acquire_ctx *ctx; | |
75 | int ret; | |
76 | ||
bf9e37ba DV |
77 | ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); |
78 | if (WARN_ON(!ctx)) | |
79 | return; | |
80 | ||
81 | mutex_lock(&config->mutex); | |
a6a8bb84 DV |
82 | |
83 | drm_modeset_acquire_init(ctx, 0); | |
84 | ||
85 | retry: | |
06eaae46 TR |
86 | ret = drm_modeset_lock_all_ctx(dev, ctx); |
87 | if (ret < 0) { | |
88 | if (ret == -EDEADLK) { | |
89 | drm_modeset_backoff(ctx); | |
90 | goto retry; | |
91 | } | |
92 | ||
93 | drm_modeset_acquire_fini(ctx); | |
94 | kfree(ctx); | |
95 | return; | |
96 | } | |
a6a8bb84 DV |
97 | |
98 | WARN_ON(config->acquire_ctx); | |
99 | ||
06eaae46 TR |
100 | /* |
101 | * We hold the locks now, so it is safe to stash the acquisition | |
102 | * context for drm_modeset_unlock_all(). | |
a6a8bb84 DV |
103 | */ |
104 | config->acquire_ctx = ctx; | |
105 | ||
106 | drm_warn_on_modeset_not_all_locked(dev); | |
a6a8bb84 DV |
107 | } |
108 | EXPORT_SYMBOL(drm_modeset_lock_all); | |
109 | ||
110 | /** | |
111 | * drm_modeset_unlock_all - drop all modeset locks | |
06eaae46 | 112 | * @dev: DRM device |
a6a8bb84 | 113 | * |
06eaae46 TR |
114 | * This function drops all modeset locks taken by a previous call to the |
115 | * drm_modeset_lock_all() function. | |
116 | * | |
117 | * This function is deprecated. It uses the lock acquisition context stored | |
118 | * in the DRM device's ->mode_config. This facilitates conversion of existing | |
119 | * code because it removes the need to manually deal with the acquisition | |
120 | * context, but it is also brittle because the context is global and care must | |
121 | * be taken not to nest calls. New code should pass the acquisition context | |
122 | * directly to the drm_modeset_drop_locks() function. | |
a6a8bb84 DV |
123 | */ |
124 | void drm_modeset_unlock_all(struct drm_device *dev) | |
125 | { | |
126 | struct drm_mode_config *config = &dev->mode_config; | |
127 | struct drm_modeset_acquire_ctx *ctx = config->acquire_ctx; | |
128 | ||
129 | if (WARN_ON(!ctx)) | |
130 | return; | |
131 | ||
132 | config->acquire_ctx = NULL; | |
133 | drm_modeset_drop_locks(ctx); | |
134 | drm_modeset_acquire_fini(ctx); | |
135 | ||
136 | kfree(ctx); | |
137 | ||
138 | mutex_unlock(&dev->mode_config.mutex); | |
139 | } | |
140 | EXPORT_SYMBOL(drm_modeset_unlock_all); | |
141 | ||
d059f652 | 142 | /** |
4d02e2de DV |
143 | * drm_modeset_lock_crtc - lock crtc with hidden acquire ctx for a plane update |
144 | * @crtc: DRM CRTC | |
145 | * @plane: DRM plane to be updated on @crtc | |
146 | * | |
147 | * This function locks the given crtc and plane (which should be either the | |
148 | * primary or cursor plane) using a hidden acquire context. This is necessary so | |
149 | * that drivers internally using the atomic interfaces can grab further locks | |
150 | * with the lock acquire context. | |
d059f652 | 151 | * |
4d02e2de DV |
152 | * Note that @plane can be NULL, e.g. when the cursor support hasn't yet been |
153 | * converted to universal planes yet. | |
d059f652 | 154 | */ |
4d02e2de DV |
155 | void drm_modeset_lock_crtc(struct drm_crtc *crtc, |
156 | struct drm_plane *plane) | |
d059f652 DV |
157 | { |
158 | struct drm_modeset_acquire_ctx *ctx; | |
159 | int ret; | |
160 | ||
161 | ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); | |
162 | if (WARN_ON(!ctx)) | |
163 | return; | |
164 | ||
165 | drm_modeset_acquire_init(ctx, 0); | |
166 | ||
167 | retry: | |
168 | ret = drm_modeset_lock(&crtc->mutex, ctx); | |
169 | if (ret) | |
170 | goto fail; | |
171 | ||
4d02e2de DV |
172 | if (plane) { |
173 | ret = drm_modeset_lock(&plane->mutex, ctx); | |
174 | if (ret) | |
175 | goto fail; | |
176 | ||
177 | if (plane->crtc) { | |
178 | ret = drm_modeset_lock(&plane->crtc->mutex, ctx); | |
179 | if (ret) | |
180 | goto fail; | |
181 | } | |
182 | } | |
183 | ||
d059f652 DV |
184 | WARN_ON(crtc->acquire_ctx); |
185 | ||
186 | /* now we hold the locks, so now that it is safe, stash the | |
187 | * ctx for drm_modeset_unlock_crtc(): | |
188 | */ | |
189 | crtc->acquire_ctx = ctx; | |
190 | ||
191 | return; | |
192 | ||
193 | fail: | |
194 | if (ret == -EDEADLK) { | |
195 | drm_modeset_backoff(ctx); | |
196 | goto retry; | |
197 | } | |
198 | } | |
199 | EXPORT_SYMBOL(drm_modeset_lock_crtc); | |
200 | ||
201 | /** | |
202 | * drm_modeset_legacy_acquire_ctx - find acquire ctx for legacy ioctls | |
295ee853 | 203 | * @crtc: drm crtc |
d059f652 DV |
204 | * |
205 | * Legacy ioctl operations like cursor updates or page flips only have per-crtc | |
206 | * locking, and store the acquire ctx in the corresponding crtc. All other | |
207 | * legacy operations take all locks and use a global acquire context. This | |
208 | * function grabs the right one. | |
209 | */ | |
210 | struct drm_modeset_acquire_ctx * | |
211 | drm_modeset_legacy_acquire_ctx(struct drm_crtc *crtc) | |
212 | { | |
213 | if (crtc->acquire_ctx) | |
214 | return crtc->acquire_ctx; | |
215 | ||
216 | WARN_ON(!crtc->dev->mode_config.acquire_ctx); | |
217 | ||
218 | return crtc->dev->mode_config.acquire_ctx; | |
219 | } | |
220 | EXPORT_SYMBOL(drm_modeset_legacy_acquire_ctx); | |
221 | ||
222 | /** | |
223 | * drm_modeset_unlock_crtc - drop crtc lock | |
224 | * @crtc: drm crtc | |
225 | * | |
226 | * This drops the crtc lock acquire with drm_modeset_lock_crtc() and all other | |
227 | * locks acquired through the hidden context. | |
228 | */ | |
229 | void drm_modeset_unlock_crtc(struct drm_crtc *crtc) | |
230 | { | |
231 | struct drm_modeset_acquire_ctx *ctx = crtc->acquire_ctx; | |
232 | ||
233 | if (WARN_ON(!ctx)) | |
234 | return; | |
235 | ||
236 | crtc->acquire_ctx = NULL; | |
237 | drm_modeset_drop_locks(ctx); | |
238 | drm_modeset_acquire_fini(ctx); | |
239 | ||
240 | kfree(ctx); | |
241 | } | |
242 | EXPORT_SYMBOL(drm_modeset_unlock_crtc); | |
243 | ||
a6a8bb84 DV |
244 | /** |
245 | * drm_warn_on_modeset_not_all_locked - check that all modeset locks are locked | |
246 | * @dev: device | |
247 | * | |
248 | * Useful as a debug assert. | |
249 | */ | |
250 | void drm_warn_on_modeset_not_all_locked(struct drm_device *dev) | |
251 | { | |
252 | struct drm_crtc *crtc; | |
253 | ||
254 | /* Locking is currently fubar in the panic handler. */ | |
255 | if (oops_in_progress) | |
256 | return; | |
257 | ||
e4f62546 | 258 | drm_for_each_crtc(crtc, dev) |
a6a8bb84 DV |
259 | WARN_ON(!drm_modeset_is_locked(&crtc->mutex)); |
260 | ||
261 | WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex)); | |
262 | WARN_ON(!mutex_is_locked(&dev->mode_config.mutex)); | |
263 | } | |
264 | EXPORT_SYMBOL(drm_warn_on_modeset_not_all_locked); | |
265 | ||
51fd371b RC |
266 | /** |
267 | * drm_modeset_acquire_init - initialize acquire context | |
268 | * @ctx: the acquire context | |
269 | * @flags: for future | |
270 | */ | |
271 | void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx, | |
272 | uint32_t flags) | |
273 | { | |
fb54918a | 274 | memset(ctx, 0, sizeof(*ctx)); |
51fd371b RC |
275 | ww_acquire_init(&ctx->ww_ctx, &crtc_ww_class); |
276 | INIT_LIST_HEAD(&ctx->locked); | |
277 | } | |
278 | EXPORT_SYMBOL(drm_modeset_acquire_init); | |
279 | ||
280 | /** | |
281 | * drm_modeset_acquire_fini - cleanup acquire context | |
282 | * @ctx: the acquire context | |
283 | */ | |
284 | void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx) | |
285 | { | |
286 | ww_acquire_fini(&ctx->ww_ctx); | |
287 | } | |
288 | EXPORT_SYMBOL(drm_modeset_acquire_fini); | |
289 | ||
290 | /** | |
291 | * drm_modeset_drop_locks - drop all locks | |
292 | * @ctx: the acquire context | |
293 | * | |
294 | * Drop all locks currently held against this acquire context. | |
295 | */ | |
296 | void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx *ctx) | |
297 | { | |
298 | WARN_ON(ctx->contended); | |
299 | while (!list_empty(&ctx->locked)) { | |
300 | struct drm_modeset_lock *lock; | |
301 | ||
302 | lock = list_first_entry(&ctx->locked, | |
303 | struct drm_modeset_lock, head); | |
304 | ||
305 | drm_modeset_unlock(lock); | |
306 | } | |
307 | } | |
308 | EXPORT_SYMBOL(drm_modeset_drop_locks); | |
309 | ||
310 | static inline int modeset_lock(struct drm_modeset_lock *lock, | |
311 | struct drm_modeset_acquire_ctx *ctx, | |
312 | bool interruptible, bool slow) | |
313 | { | |
314 | int ret; | |
315 | ||
316 | WARN_ON(ctx->contended); | |
317 | ||
cb597bb3 | 318 | if (ctx->trylock_only) { |
825926d8 ML |
319 | lockdep_assert_held(&ctx->ww_ctx); |
320 | ||
cb597bb3 DV |
321 | if (!ww_mutex_trylock(&lock->mutex)) |
322 | return -EBUSY; | |
323 | else | |
324 | return 0; | |
325 | } else if (interruptible && slow) { | |
51fd371b RC |
326 | ret = ww_mutex_lock_slow_interruptible(&lock->mutex, &ctx->ww_ctx); |
327 | } else if (interruptible) { | |
328 | ret = ww_mutex_lock_interruptible(&lock->mutex, &ctx->ww_ctx); | |
329 | } else if (slow) { | |
330 | ww_mutex_lock_slow(&lock->mutex, &ctx->ww_ctx); | |
331 | ret = 0; | |
332 | } else { | |
333 | ret = ww_mutex_lock(&lock->mutex, &ctx->ww_ctx); | |
334 | } | |
335 | if (!ret) { | |
336 | WARN_ON(!list_empty(&lock->head)); | |
337 | list_add(&lock->head, &ctx->locked); | |
338 | } else if (ret == -EALREADY) { | |
339 | /* we already hold the lock.. this is fine. For atomic | |
340 | * we will need to be able to drm_modeset_lock() things | |
341 | * without having to keep track of what is already locked | |
342 | * or not. | |
343 | */ | |
344 | ret = 0; | |
345 | } else if (ret == -EDEADLK) { | |
346 | ctx->contended = lock; | |
347 | } | |
348 | ||
349 | return ret; | |
350 | } | |
351 | ||
352 | static int modeset_backoff(struct drm_modeset_acquire_ctx *ctx, | |
353 | bool interruptible) | |
354 | { | |
355 | struct drm_modeset_lock *contended = ctx->contended; | |
356 | ||
357 | ctx->contended = NULL; | |
358 | ||
359 | if (WARN_ON(!contended)) | |
360 | return 0; | |
361 | ||
362 | drm_modeset_drop_locks(ctx); | |
363 | ||
364 | return modeset_lock(contended, ctx, interruptible, true); | |
365 | } | |
366 | ||
367 | /** | |
368 | * drm_modeset_backoff - deadlock avoidance backoff | |
369 | * @ctx: the acquire context | |
370 | * | |
371 | * If deadlock is detected (ie. drm_modeset_lock() returns -EDEADLK), | |
372 | * you must call this function to drop all currently held locks and | |
373 | * block until the contended lock becomes available. | |
374 | */ | |
375 | void drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx) | |
376 | { | |
377 | modeset_backoff(ctx, false); | |
378 | } | |
379 | EXPORT_SYMBOL(drm_modeset_backoff); | |
380 | ||
381 | /** | |
382 | * drm_modeset_backoff_interruptible - deadlock avoidance backoff | |
383 | * @ctx: the acquire context | |
384 | * | |
385 | * Interruptible version of drm_modeset_backoff() | |
386 | */ | |
387 | int drm_modeset_backoff_interruptible(struct drm_modeset_acquire_ctx *ctx) | |
388 | { | |
389 | return modeset_backoff(ctx, true); | |
390 | } | |
391 | EXPORT_SYMBOL(drm_modeset_backoff_interruptible); | |
392 | ||
393 | /** | |
394 | * drm_modeset_lock - take modeset lock | |
395 | * @lock: lock to take | |
396 | * @ctx: acquire ctx | |
397 | * | |
398 | * If ctx is not NULL, then its ww acquire context is used and the | |
399 | * lock will be tracked by the context and can be released by calling | |
400 | * drm_modeset_drop_locks(). If -EDEADLK is returned, this means a | |
401 | * deadlock scenario has been detected and it is an error to attempt | |
402 | * to take any more locks without first calling drm_modeset_backoff(). | |
403 | */ | |
404 | int drm_modeset_lock(struct drm_modeset_lock *lock, | |
405 | struct drm_modeset_acquire_ctx *ctx) | |
406 | { | |
407 | if (ctx) | |
408 | return modeset_lock(lock, ctx, false, false); | |
409 | ||
410 | ww_mutex_lock(&lock->mutex, NULL); | |
411 | return 0; | |
412 | } | |
413 | EXPORT_SYMBOL(drm_modeset_lock); | |
414 | ||
415 | /** | |
416 | * drm_modeset_lock_interruptible - take modeset lock | |
417 | * @lock: lock to take | |
418 | * @ctx: acquire ctx | |
419 | * | |
420 | * Interruptible version of drm_modeset_lock() | |
421 | */ | |
422 | int drm_modeset_lock_interruptible(struct drm_modeset_lock *lock, | |
423 | struct drm_modeset_acquire_ctx *ctx) | |
424 | { | |
425 | if (ctx) | |
426 | return modeset_lock(lock, ctx, true, false); | |
427 | ||
428 | return ww_mutex_lock_interruptible(&lock->mutex, NULL); | |
429 | } | |
430 | EXPORT_SYMBOL(drm_modeset_lock_interruptible); | |
431 | ||
432 | /** | |
433 | * drm_modeset_unlock - drop modeset lock | |
434 | * @lock: lock to release | |
435 | */ | |
436 | void drm_modeset_unlock(struct drm_modeset_lock *lock) | |
437 | { | |
438 | list_del_init(&lock->head); | |
439 | ww_mutex_unlock(&lock->mutex); | |
440 | } | |
441 | EXPORT_SYMBOL(drm_modeset_unlock); | |
442 | ||
06eaae46 TR |
443 | /** |
444 | * drm_modeset_lock_all_ctx - take all modeset locks | |
445 | * @dev: DRM device | |
446 | * @ctx: lock acquisition context | |
447 | * | |
448 | * This function takes all modeset locks, suitable where a more fine-grained | |
449 | * scheme isn't (yet) implemented. | |
450 | * | |
451 | * Unlike drm_modeset_lock_all(), it doesn't take the dev->mode_config.mutex | |
452 | * since that lock isn't required for modeset state changes. Callers which | |
453 | * need to grab that lock too need to do so outside of the acquire context | |
454 | * @ctx. | |
455 | * | |
456 | * Locks acquired with this function should be released by calling the | |
457 | * drm_modeset_drop_locks() function on @ctx. | |
458 | * | |
459 | * Returns: 0 on success or a negative error-code on failure. | |
460 | */ | |
461 | int drm_modeset_lock_all_ctx(struct drm_device *dev, | |
462 | struct drm_modeset_acquire_ctx *ctx) | |
51fd371b | 463 | { |
51fd371b | 464 | struct drm_crtc *crtc; |
4d02e2de | 465 | struct drm_plane *plane; |
06eaae46 TR |
466 | int ret; |
467 | ||
468 | ret = drm_modeset_lock(&dev->mode_config.connection_mutex, ctx); | |
469 | if (ret) | |
470 | return ret; | |
51fd371b | 471 | |
e4f62546 | 472 | drm_for_each_crtc(crtc, dev) { |
51fd371b RC |
473 | ret = drm_modeset_lock(&crtc->mutex, ctx); |
474 | if (ret) | |
475 | return ret; | |
476 | } | |
477 | ||
e4f62546 | 478 | drm_for_each_plane(plane, dev) { |
4d02e2de DV |
479 | ret = drm_modeset_lock(&plane->mutex, ctx); |
480 | if (ret) | |
481 | return ret; | |
482 | } | |
483 | ||
51fd371b RC |
484 | return 0; |
485 | } | |
06eaae46 | 486 | EXPORT_SYMBOL(drm_modeset_lock_all_ctx); |