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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 | |
0645de5a | 33 | * to use &ww_mutex and acquire-contexts to avoid deadlocks. But because |
51fd371b RC |
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 | * | |
0645de5a | 38 | * For basic principles of &ww_mutex, see: Documentation/locking/ww-mutex-design.txt |
51fd371b | 39 | * |
da5335b8 | 40 | * The basic usage pattern is to:: |
51fd371b RC |
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); | |
0645de5a DV |
54 | * |
55 | * On top of of these per-object locks using &ww_mutex there's also an overall | |
56 | * dev->mode_config.lock, for protecting everything else. Mostly this means | |
57 | * probe state of connectors, and preventing hotplug add/removal of connectors. | |
58 | * | |
59 | * Finally there's a bunch of dedicated locks to protect drm core internal | |
60 | * lists and lookup data structures. | |
51fd371b RC |
61 | */ |
62 | ||
a6a8bb84 | 63 | /** |
bf9e37ba | 64 | * drm_modeset_lock_all - take all modeset locks |
06eaae46 | 65 | * @dev: DRM device |
cb597bb3 | 66 | * |
bf9e37ba | 67 | * This function takes all modeset locks, suitable where a more fine-grained |
06eaae46 TR |
68 | * scheme isn't (yet) implemented. Locks must be dropped by calling the |
69 | * drm_modeset_unlock_all() function. | |
70 | * | |
71 | * This function is deprecated. It allocates a lock acquisition context and | |
72 | * stores it in the DRM device's ->mode_config. This facilitate conversion of | |
73 | * existing code because it removes the need to manually deal with the | |
74 | * acquisition context, but it is also brittle because the context is global | |
75 | * and care must be taken not to nest calls. New code should use the | |
76 | * drm_modeset_lock_all_ctx() function and pass in the context explicitly. | |
a6a8bb84 | 77 | */ |
bf9e37ba | 78 | void drm_modeset_lock_all(struct drm_device *dev) |
a6a8bb84 DV |
79 | { |
80 | struct drm_mode_config *config = &dev->mode_config; | |
81 | struct drm_modeset_acquire_ctx *ctx; | |
82 | int ret; | |
83 | ||
bf9e37ba DV |
84 | ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); |
85 | if (WARN_ON(!ctx)) | |
86 | return; | |
87 | ||
88 | mutex_lock(&config->mutex); | |
a6a8bb84 DV |
89 | |
90 | drm_modeset_acquire_init(ctx, 0); | |
91 | ||
92 | retry: | |
06eaae46 TR |
93 | ret = drm_modeset_lock_all_ctx(dev, ctx); |
94 | if (ret < 0) { | |
95 | if (ret == -EDEADLK) { | |
96 | drm_modeset_backoff(ctx); | |
97 | goto retry; | |
98 | } | |
99 | ||
100 | drm_modeset_acquire_fini(ctx); | |
101 | kfree(ctx); | |
102 | return; | |
103 | } | |
a6a8bb84 DV |
104 | |
105 | WARN_ON(config->acquire_ctx); | |
106 | ||
06eaae46 TR |
107 | /* |
108 | * We hold the locks now, so it is safe to stash the acquisition | |
109 | * context for drm_modeset_unlock_all(). | |
a6a8bb84 DV |
110 | */ |
111 | config->acquire_ctx = ctx; | |
112 | ||
113 | drm_warn_on_modeset_not_all_locked(dev); | |
a6a8bb84 DV |
114 | } |
115 | EXPORT_SYMBOL(drm_modeset_lock_all); | |
116 | ||
117 | /** | |
118 | * drm_modeset_unlock_all - drop all modeset locks | |
06eaae46 | 119 | * @dev: DRM device |
a6a8bb84 | 120 | * |
06eaae46 TR |
121 | * This function drops all modeset locks taken by a previous call to the |
122 | * drm_modeset_lock_all() function. | |
123 | * | |
124 | * This function is deprecated. It uses the lock acquisition context stored | |
125 | * in the DRM device's ->mode_config. This facilitates conversion of existing | |
126 | * code because it removes the need to manually deal with the acquisition | |
127 | * context, but it is also brittle because the context is global and care must | |
128 | * be taken not to nest calls. New code should pass the acquisition context | |
129 | * directly to the drm_modeset_drop_locks() function. | |
a6a8bb84 DV |
130 | */ |
131 | void drm_modeset_unlock_all(struct drm_device *dev) | |
132 | { | |
133 | struct drm_mode_config *config = &dev->mode_config; | |
134 | struct drm_modeset_acquire_ctx *ctx = config->acquire_ctx; | |
135 | ||
136 | if (WARN_ON(!ctx)) | |
137 | return; | |
138 | ||
139 | config->acquire_ctx = NULL; | |
140 | drm_modeset_drop_locks(ctx); | |
141 | drm_modeset_acquire_fini(ctx); | |
142 | ||
143 | kfree(ctx); | |
144 | ||
145 | mutex_unlock(&dev->mode_config.mutex); | |
146 | } | |
147 | EXPORT_SYMBOL(drm_modeset_unlock_all); | |
148 | ||
d059f652 | 149 | /** |
4d02e2de DV |
150 | * drm_modeset_lock_crtc - lock crtc with hidden acquire ctx for a plane update |
151 | * @crtc: DRM CRTC | |
152 | * @plane: DRM plane to be updated on @crtc | |
153 | * | |
154 | * This function locks the given crtc and plane (which should be either the | |
155 | * primary or cursor plane) using a hidden acquire context. This is necessary so | |
156 | * that drivers internally using the atomic interfaces can grab further locks | |
157 | * with the lock acquire context. | |
d059f652 | 158 | * |
4d02e2de DV |
159 | * Note that @plane can be NULL, e.g. when the cursor support hasn't yet been |
160 | * converted to universal planes yet. | |
d059f652 | 161 | */ |
4d02e2de DV |
162 | void drm_modeset_lock_crtc(struct drm_crtc *crtc, |
163 | struct drm_plane *plane) | |
d059f652 DV |
164 | { |
165 | struct drm_modeset_acquire_ctx *ctx; | |
166 | int ret; | |
167 | ||
168 | ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); | |
169 | if (WARN_ON(!ctx)) | |
170 | return; | |
171 | ||
172 | drm_modeset_acquire_init(ctx, 0); | |
173 | ||
174 | retry: | |
175 | ret = drm_modeset_lock(&crtc->mutex, ctx); | |
176 | if (ret) | |
177 | goto fail; | |
178 | ||
4d02e2de DV |
179 | if (plane) { |
180 | ret = drm_modeset_lock(&plane->mutex, ctx); | |
181 | if (ret) | |
182 | goto fail; | |
183 | ||
184 | if (plane->crtc) { | |
185 | ret = drm_modeset_lock(&plane->crtc->mutex, ctx); | |
186 | if (ret) | |
187 | goto fail; | |
188 | } | |
189 | } | |
190 | ||
d059f652 DV |
191 | WARN_ON(crtc->acquire_ctx); |
192 | ||
193 | /* now we hold the locks, so now that it is safe, stash the | |
194 | * ctx for drm_modeset_unlock_crtc(): | |
195 | */ | |
196 | crtc->acquire_ctx = ctx; | |
197 | ||
198 | return; | |
199 | ||
200 | fail: | |
201 | if (ret == -EDEADLK) { | |
202 | drm_modeset_backoff(ctx); | |
203 | goto retry; | |
204 | } | |
205 | } | |
206 | EXPORT_SYMBOL(drm_modeset_lock_crtc); | |
207 | ||
208 | /** | |
209 | * drm_modeset_legacy_acquire_ctx - find acquire ctx for legacy ioctls | |
295ee853 | 210 | * @crtc: drm crtc |
d059f652 DV |
211 | * |
212 | * Legacy ioctl operations like cursor updates or page flips only have per-crtc | |
213 | * locking, and store the acquire ctx in the corresponding crtc. All other | |
214 | * legacy operations take all locks and use a global acquire context. This | |
215 | * function grabs the right one. | |
216 | */ | |
217 | struct drm_modeset_acquire_ctx * | |
218 | drm_modeset_legacy_acquire_ctx(struct drm_crtc *crtc) | |
219 | { | |
220 | if (crtc->acquire_ctx) | |
221 | return crtc->acquire_ctx; | |
222 | ||
223 | WARN_ON(!crtc->dev->mode_config.acquire_ctx); | |
224 | ||
225 | return crtc->dev->mode_config.acquire_ctx; | |
226 | } | |
227 | EXPORT_SYMBOL(drm_modeset_legacy_acquire_ctx); | |
228 | ||
229 | /** | |
230 | * drm_modeset_unlock_crtc - drop crtc lock | |
231 | * @crtc: drm crtc | |
232 | * | |
233 | * This drops the crtc lock acquire with drm_modeset_lock_crtc() and all other | |
234 | * locks acquired through the hidden context. | |
235 | */ | |
236 | void drm_modeset_unlock_crtc(struct drm_crtc *crtc) | |
237 | { | |
238 | struct drm_modeset_acquire_ctx *ctx = crtc->acquire_ctx; | |
239 | ||
240 | if (WARN_ON(!ctx)) | |
241 | return; | |
242 | ||
243 | crtc->acquire_ctx = NULL; | |
244 | drm_modeset_drop_locks(ctx); | |
245 | drm_modeset_acquire_fini(ctx); | |
246 | ||
247 | kfree(ctx); | |
248 | } | |
249 | EXPORT_SYMBOL(drm_modeset_unlock_crtc); | |
250 | ||
a6a8bb84 DV |
251 | /** |
252 | * drm_warn_on_modeset_not_all_locked - check that all modeset locks are locked | |
253 | * @dev: device | |
254 | * | |
255 | * Useful as a debug assert. | |
256 | */ | |
257 | void drm_warn_on_modeset_not_all_locked(struct drm_device *dev) | |
258 | { | |
259 | struct drm_crtc *crtc; | |
260 | ||
261 | /* Locking is currently fubar in the panic handler. */ | |
262 | if (oops_in_progress) | |
263 | return; | |
264 | ||
e4f62546 | 265 | drm_for_each_crtc(crtc, dev) |
a6a8bb84 DV |
266 | WARN_ON(!drm_modeset_is_locked(&crtc->mutex)); |
267 | ||
268 | WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex)); | |
269 | WARN_ON(!mutex_is_locked(&dev->mode_config.mutex)); | |
270 | } | |
271 | EXPORT_SYMBOL(drm_warn_on_modeset_not_all_locked); | |
272 | ||
51fd371b RC |
273 | /** |
274 | * drm_modeset_acquire_init - initialize acquire context | |
275 | * @ctx: the acquire context | |
276 | * @flags: for future | |
277 | */ | |
278 | void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx, | |
279 | uint32_t flags) | |
280 | { | |
fb54918a | 281 | memset(ctx, 0, sizeof(*ctx)); |
51fd371b RC |
282 | ww_acquire_init(&ctx->ww_ctx, &crtc_ww_class); |
283 | INIT_LIST_HEAD(&ctx->locked); | |
284 | } | |
285 | EXPORT_SYMBOL(drm_modeset_acquire_init); | |
286 | ||
287 | /** | |
288 | * drm_modeset_acquire_fini - cleanup acquire context | |
289 | * @ctx: the acquire context | |
290 | */ | |
291 | void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx) | |
292 | { | |
293 | ww_acquire_fini(&ctx->ww_ctx); | |
294 | } | |
295 | EXPORT_SYMBOL(drm_modeset_acquire_fini); | |
296 | ||
297 | /** | |
298 | * drm_modeset_drop_locks - drop all locks | |
299 | * @ctx: the acquire context | |
300 | * | |
301 | * Drop all locks currently held against this acquire context. | |
302 | */ | |
303 | void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx *ctx) | |
304 | { | |
305 | WARN_ON(ctx->contended); | |
306 | while (!list_empty(&ctx->locked)) { | |
307 | struct drm_modeset_lock *lock; | |
308 | ||
309 | lock = list_first_entry(&ctx->locked, | |
310 | struct drm_modeset_lock, head); | |
311 | ||
312 | drm_modeset_unlock(lock); | |
313 | } | |
314 | } | |
315 | EXPORT_SYMBOL(drm_modeset_drop_locks); | |
316 | ||
317 | static inline int modeset_lock(struct drm_modeset_lock *lock, | |
318 | struct drm_modeset_acquire_ctx *ctx, | |
319 | bool interruptible, bool slow) | |
320 | { | |
321 | int ret; | |
322 | ||
323 | WARN_ON(ctx->contended); | |
324 | ||
cb597bb3 | 325 | if (ctx->trylock_only) { |
825926d8 ML |
326 | lockdep_assert_held(&ctx->ww_ctx); |
327 | ||
cb597bb3 DV |
328 | if (!ww_mutex_trylock(&lock->mutex)) |
329 | return -EBUSY; | |
330 | else | |
331 | return 0; | |
332 | } else if (interruptible && slow) { | |
51fd371b RC |
333 | ret = ww_mutex_lock_slow_interruptible(&lock->mutex, &ctx->ww_ctx); |
334 | } else if (interruptible) { | |
335 | ret = ww_mutex_lock_interruptible(&lock->mutex, &ctx->ww_ctx); | |
336 | } else if (slow) { | |
337 | ww_mutex_lock_slow(&lock->mutex, &ctx->ww_ctx); | |
338 | ret = 0; | |
339 | } else { | |
340 | ret = ww_mutex_lock(&lock->mutex, &ctx->ww_ctx); | |
341 | } | |
342 | if (!ret) { | |
343 | WARN_ON(!list_empty(&lock->head)); | |
344 | list_add(&lock->head, &ctx->locked); | |
345 | } else if (ret == -EALREADY) { | |
346 | /* we already hold the lock.. this is fine. For atomic | |
347 | * we will need to be able to drm_modeset_lock() things | |
348 | * without having to keep track of what is already locked | |
349 | * or not. | |
350 | */ | |
351 | ret = 0; | |
352 | } else if (ret == -EDEADLK) { | |
353 | ctx->contended = lock; | |
354 | } | |
355 | ||
356 | return ret; | |
357 | } | |
358 | ||
359 | static int modeset_backoff(struct drm_modeset_acquire_ctx *ctx, | |
360 | bool interruptible) | |
361 | { | |
362 | struct drm_modeset_lock *contended = ctx->contended; | |
363 | ||
364 | ctx->contended = NULL; | |
365 | ||
366 | if (WARN_ON(!contended)) | |
367 | return 0; | |
368 | ||
369 | drm_modeset_drop_locks(ctx); | |
370 | ||
371 | return modeset_lock(contended, ctx, interruptible, true); | |
372 | } | |
373 | ||
374 | /** | |
375 | * drm_modeset_backoff - deadlock avoidance backoff | |
376 | * @ctx: the acquire context | |
377 | * | |
378 | * If deadlock is detected (ie. drm_modeset_lock() returns -EDEADLK), | |
379 | * you must call this function to drop all currently held locks and | |
380 | * block until the contended lock becomes available. | |
381 | */ | |
382 | void drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx) | |
383 | { | |
384 | modeset_backoff(ctx, false); | |
385 | } | |
386 | EXPORT_SYMBOL(drm_modeset_backoff); | |
387 | ||
388 | /** | |
389 | * drm_modeset_backoff_interruptible - deadlock avoidance backoff | |
390 | * @ctx: the acquire context | |
391 | * | |
392 | * Interruptible version of drm_modeset_backoff() | |
393 | */ | |
394 | int drm_modeset_backoff_interruptible(struct drm_modeset_acquire_ctx *ctx) | |
395 | { | |
396 | return modeset_backoff(ctx, true); | |
397 | } | |
398 | EXPORT_SYMBOL(drm_modeset_backoff_interruptible); | |
399 | ||
400 | /** | |
401 | * drm_modeset_lock - take modeset lock | |
402 | * @lock: lock to take | |
403 | * @ctx: acquire ctx | |
404 | * | |
405 | * If ctx is not NULL, then its ww acquire context is used and the | |
406 | * lock will be tracked by the context and can be released by calling | |
407 | * drm_modeset_drop_locks(). If -EDEADLK is returned, this means a | |
408 | * deadlock scenario has been detected and it is an error to attempt | |
409 | * to take any more locks without first calling drm_modeset_backoff(). | |
410 | */ | |
411 | int drm_modeset_lock(struct drm_modeset_lock *lock, | |
412 | struct drm_modeset_acquire_ctx *ctx) | |
413 | { | |
414 | if (ctx) | |
415 | return modeset_lock(lock, ctx, false, false); | |
416 | ||
417 | ww_mutex_lock(&lock->mutex, NULL); | |
418 | return 0; | |
419 | } | |
420 | EXPORT_SYMBOL(drm_modeset_lock); | |
421 | ||
422 | /** | |
423 | * drm_modeset_lock_interruptible - take modeset lock | |
424 | * @lock: lock to take | |
425 | * @ctx: acquire ctx | |
426 | * | |
427 | * Interruptible version of drm_modeset_lock() | |
428 | */ | |
429 | int drm_modeset_lock_interruptible(struct drm_modeset_lock *lock, | |
430 | struct drm_modeset_acquire_ctx *ctx) | |
431 | { | |
432 | if (ctx) | |
433 | return modeset_lock(lock, ctx, true, false); | |
434 | ||
435 | return ww_mutex_lock_interruptible(&lock->mutex, NULL); | |
436 | } | |
437 | EXPORT_SYMBOL(drm_modeset_lock_interruptible); | |
438 | ||
439 | /** | |
440 | * drm_modeset_unlock - drop modeset lock | |
441 | * @lock: lock to release | |
442 | */ | |
443 | void drm_modeset_unlock(struct drm_modeset_lock *lock) | |
444 | { | |
445 | list_del_init(&lock->head); | |
446 | ww_mutex_unlock(&lock->mutex); | |
447 | } | |
448 | EXPORT_SYMBOL(drm_modeset_unlock); | |
449 | ||
06eaae46 TR |
450 | /** |
451 | * drm_modeset_lock_all_ctx - take all modeset locks | |
452 | * @dev: DRM device | |
453 | * @ctx: lock acquisition context | |
454 | * | |
455 | * This function takes all modeset locks, suitable where a more fine-grained | |
456 | * scheme isn't (yet) implemented. | |
457 | * | |
458 | * Unlike drm_modeset_lock_all(), it doesn't take the dev->mode_config.mutex | |
459 | * since that lock isn't required for modeset state changes. Callers which | |
460 | * need to grab that lock too need to do so outside of the acquire context | |
461 | * @ctx. | |
462 | * | |
463 | * Locks acquired with this function should be released by calling the | |
464 | * drm_modeset_drop_locks() function on @ctx. | |
465 | * | |
466 | * Returns: 0 on success or a negative error-code on failure. | |
467 | */ | |
468 | int drm_modeset_lock_all_ctx(struct drm_device *dev, | |
469 | struct drm_modeset_acquire_ctx *ctx) | |
51fd371b | 470 | { |
51fd371b | 471 | struct drm_crtc *crtc; |
4d02e2de | 472 | struct drm_plane *plane; |
06eaae46 TR |
473 | int ret; |
474 | ||
475 | ret = drm_modeset_lock(&dev->mode_config.connection_mutex, ctx); | |
476 | if (ret) | |
477 | return ret; | |
51fd371b | 478 | |
e4f62546 | 479 | drm_for_each_crtc(crtc, dev) { |
51fd371b RC |
480 | ret = drm_modeset_lock(&crtc->mutex, ctx); |
481 | if (ret) | |
482 | return ret; | |
483 | } | |
484 | ||
e4f62546 | 485 | drm_for_each_plane(plane, dev) { |
4d02e2de DV |
486 | ret = drm_modeset_lock(&plane->mutex, ctx); |
487 | if (ret) | |
488 | return ret; | |
489 | } | |
490 | ||
51fd371b RC |
491 | return 0; |
492 | } | |
06eaae46 | 493 | EXPORT_SYMBOL(drm_modeset_lock_all_ctx); |