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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 | |
d574528a | 36 | * by &struct drm_modeset_lock and &struct drm_modeset_acquire_ctx. |
51fd371b | 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 | 54 | * |
b07c4254 | 55 | * On top of of these per-object locks using &ww_mutex there's also an overall |
d574528a | 56 | * &drm_mode_config.mutex, for protecting everything else. Mostly this means |
b07c4254 | 57 | * probe state of connectors, and preventing hotplug add/removal of connectors. |
0645de5a | 58 | * |
b07c4254 DV |
59 | * Finally there's a bunch of dedicated locks to protect drm core internal |
60 | * lists and lookup data structures. | |
51fd371b RC |
61 | */ |
62 | ||
35cf0350 RC |
63 | static DEFINE_WW_CLASS(crtc_ww_class); |
64 | ||
a6a8bb84 | 65 | /** |
bf9e37ba | 66 | * drm_modeset_lock_all - take all modeset locks |
06eaae46 | 67 | * @dev: DRM device |
cb597bb3 | 68 | * |
bf9e37ba | 69 | * This function takes all modeset locks, suitable where a more fine-grained |
06eaae46 TR |
70 | * scheme isn't (yet) implemented. Locks must be dropped by calling the |
71 | * drm_modeset_unlock_all() function. | |
72 | * | |
73 | * This function is deprecated. It allocates a lock acquisition context and | |
d574528a | 74 | * stores it in &drm_device.mode_config. This facilitate conversion of |
06eaae46 TR |
75 | * existing code because it removes the need to manually deal with the |
76 | * acquisition context, but it is also brittle because the context is global | |
77 | * and care must be taken not to nest calls. New code should use the | |
78 | * drm_modeset_lock_all_ctx() function and pass in the context explicitly. | |
a6a8bb84 | 79 | */ |
bf9e37ba | 80 | void drm_modeset_lock_all(struct drm_device *dev) |
a6a8bb84 DV |
81 | { |
82 | struct drm_mode_config *config = &dev->mode_config; | |
83 | struct drm_modeset_acquire_ctx *ctx; | |
84 | int ret; | |
85 | ||
bf9e37ba DV |
86 | ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); |
87 | if (WARN_ON(!ctx)) | |
88 | return; | |
89 | ||
90 | mutex_lock(&config->mutex); | |
a6a8bb84 DV |
91 | |
92 | drm_modeset_acquire_init(ctx, 0); | |
93 | ||
94 | retry: | |
06eaae46 TR |
95 | ret = drm_modeset_lock_all_ctx(dev, ctx); |
96 | if (ret < 0) { | |
97 | if (ret == -EDEADLK) { | |
98 | drm_modeset_backoff(ctx); | |
99 | goto retry; | |
100 | } | |
101 | ||
102 | drm_modeset_acquire_fini(ctx); | |
103 | kfree(ctx); | |
104 | return; | |
105 | } | |
a6a8bb84 DV |
106 | |
107 | WARN_ON(config->acquire_ctx); | |
108 | ||
06eaae46 TR |
109 | /* |
110 | * We hold the locks now, so it is safe to stash the acquisition | |
111 | * context for drm_modeset_unlock_all(). | |
a6a8bb84 DV |
112 | */ |
113 | config->acquire_ctx = ctx; | |
114 | ||
115 | drm_warn_on_modeset_not_all_locked(dev); | |
a6a8bb84 DV |
116 | } |
117 | EXPORT_SYMBOL(drm_modeset_lock_all); | |
118 | ||
119 | /** | |
120 | * drm_modeset_unlock_all - drop all modeset locks | |
06eaae46 | 121 | * @dev: DRM device |
a6a8bb84 | 122 | * |
06eaae46 TR |
123 | * This function drops all modeset locks taken by a previous call to the |
124 | * drm_modeset_lock_all() function. | |
125 | * | |
126 | * This function is deprecated. It uses the lock acquisition context stored | |
d574528a | 127 | * in &drm_device.mode_config. This facilitates conversion of existing |
06eaae46 TR |
128 | * code because it removes the need to manually deal with the acquisition |
129 | * context, but it is also brittle because the context is global and care must | |
130 | * be taken not to nest calls. New code should pass the acquisition context | |
131 | * directly to the drm_modeset_drop_locks() function. | |
a6a8bb84 DV |
132 | */ |
133 | void drm_modeset_unlock_all(struct drm_device *dev) | |
134 | { | |
135 | struct drm_mode_config *config = &dev->mode_config; | |
136 | struct drm_modeset_acquire_ctx *ctx = config->acquire_ctx; | |
137 | ||
138 | if (WARN_ON(!ctx)) | |
139 | return; | |
140 | ||
141 | config->acquire_ctx = NULL; | |
142 | drm_modeset_drop_locks(ctx); | |
143 | drm_modeset_acquire_fini(ctx); | |
144 | ||
145 | kfree(ctx); | |
146 | ||
147 | mutex_unlock(&dev->mode_config.mutex); | |
148 | } | |
149 | EXPORT_SYMBOL(drm_modeset_unlock_all); | |
150 | ||
151 | /** | |
152 | * drm_warn_on_modeset_not_all_locked - check that all modeset locks are locked | |
153 | * @dev: device | |
154 | * | |
155 | * Useful as a debug assert. | |
156 | */ | |
157 | void drm_warn_on_modeset_not_all_locked(struct drm_device *dev) | |
158 | { | |
159 | struct drm_crtc *crtc; | |
160 | ||
161 | /* Locking is currently fubar in the panic handler. */ | |
162 | if (oops_in_progress) | |
163 | return; | |
164 | ||
e4f62546 | 165 | drm_for_each_crtc(crtc, dev) |
a6a8bb84 DV |
166 | WARN_ON(!drm_modeset_is_locked(&crtc->mutex)); |
167 | ||
168 | WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex)); | |
169 | WARN_ON(!mutex_is_locked(&dev->mode_config.mutex)); | |
170 | } | |
171 | EXPORT_SYMBOL(drm_warn_on_modeset_not_all_locked); | |
172 | ||
51fd371b RC |
173 | /** |
174 | * drm_modeset_acquire_init - initialize acquire context | |
175 | * @ctx: the acquire context | |
176 | * @flags: for future | |
177 | */ | |
178 | void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx, | |
179 | uint32_t flags) | |
180 | { | |
fb54918a | 181 | memset(ctx, 0, sizeof(*ctx)); |
51fd371b RC |
182 | ww_acquire_init(&ctx->ww_ctx, &crtc_ww_class); |
183 | INIT_LIST_HEAD(&ctx->locked); | |
184 | } | |
185 | EXPORT_SYMBOL(drm_modeset_acquire_init); | |
186 | ||
187 | /** | |
188 | * drm_modeset_acquire_fini - cleanup acquire context | |
189 | * @ctx: the acquire context | |
190 | */ | |
191 | void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx) | |
192 | { | |
193 | ww_acquire_fini(&ctx->ww_ctx); | |
194 | } | |
195 | EXPORT_SYMBOL(drm_modeset_acquire_fini); | |
196 | ||
197 | /** | |
198 | * drm_modeset_drop_locks - drop all locks | |
199 | * @ctx: the acquire context | |
200 | * | |
201 | * Drop all locks currently held against this acquire context. | |
202 | */ | |
203 | void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx *ctx) | |
204 | { | |
205 | WARN_ON(ctx->contended); | |
206 | while (!list_empty(&ctx->locked)) { | |
207 | struct drm_modeset_lock *lock; | |
208 | ||
209 | lock = list_first_entry(&ctx->locked, | |
210 | struct drm_modeset_lock, head); | |
211 | ||
212 | drm_modeset_unlock(lock); | |
213 | } | |
214 | } | |
215 | EXPORT_SYMBOL(drm_modeset_drop_locks); | |
216 | ||
217 | static inline int modeset_lock(struct drm_modeset_lock *lock, | |
218 | struct drm_modeset_acquire_ctx *ctx, | |
219 | bool interruptible, bool slow) | |
220 | { | |
221 | int ret; | |
222 | ||
223 | WARN_ON(ctx->contended); | |
224 | ||
cb597bb3 | 225 | if (ctx->trylock_only) { |
825926d8 ML |
226 | lockdep_assert_held(&ctx->ww_ctx); |
227 | ||
cb597bb3 DV |
228 | if (!ww_mutex_trylock(&lock->mutex)) |
229 | return -EBUSY; | |
230 | else | |
231 | return 0; | |
232 | } else if (interruptible && slow) { | |
51fd371b RC |
233 | ret = ww_mutex_lock_slow_interruptible(&lock->mutex, &ctx->ww_ctx); |
234 | } else if (interruptible) { | |
235 | ret = ww_mutex_lock_interruptible(&lock->mutex, &ctx->ww_ctx); | |
236 | } else if (slow) { | |
237 | ww_mutex_lock_slow(&lock->mutex, &ctx->ww_ctx); | |
238 | ret = 0; | |
239 | } else { | |
240 | ret = ww_mutex_lock(&lock->mutex, &ctx->ww_ctx); | |
241 | } | |
242 | if (!ret) { | |
243 | WARN_ON(!list_empty(&lock->head)); | |
244 | list_add(&lock->head, &ctx->locked); | |
245 | } else if (ret == -EALREADY) { | |
246 | /* we already hold the lock.. this is fine. For atomic | |
247 | * we will need to be able to drm_modeset_lock() things | |
248 | * without having to keep track of what is already locked | |
249 | * or not. | |
250 | */ | |
251 | ret = 0; | |
252 | } else if (ret == -EDEADLK) { | |
253 | ctx->contended = lock; | |
254 | } | |
255 | ||
256 | return ret; | |
257 | } | |
258 | ||
259 | static int modeset_backoff(struct drm_modeset_acquire_ctx *ctx, | |
260 | bool interruptible) | |
261 | { | |
262 | struct drm_modeset_lock *contended = ctx->contended; | |
263 | ||
264 | ctx->contended = NULL; | |
265 | ||
266 | if (WARN_ON(!contended)) | |
267 | return 0; | |
268 | ||
269 | drm_modeset_drop_locks(ctx); | |
270 | ||
271 | return modeset_lock(contended, ctx, interruptible, true); | |
272 | } | |
273 | ||
274 | /** | |
275 | * drm_modeset_backoff - deadlock avoidance backoff | |
276 | * @ctx: the acquire context | |
277 | * | |
278 | * If deadlock is detected (ie. drm_modeset_lock() returns -EDEADLK), | |
279 | * you must call this function to drop all currently held locks and | |
280 | * block until the contended lock becomes available. | |
281 | */ | |
282 | void drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx) | |
283 | { | |
284 | modeset_backoff(ctx, false); | |
285 | } | |
286 | EXPORT_SYMBOL(drm_modeset_backoff); | |
287 | ||
288 | /** | |
289 | * drm_modeset_backoff_interruptible - deadlock avoidance backoff | |
290 | * @ctx: the acquire context | |
291 | * | |
292 | * Interruptible version of drm_modeset_backoff() | |
293 | */ | |
294 | int drm_modeset_backoff_interruptible(struct drm_modeset_acquire_ctx *ctx) | |
295 | { | |
296 | return modeset_backoff(ctx, true); | |
297 | } | |
298 | EXPORT_SYMBOL(drm_modeset_backoff_interruptible); | |
299 | ||
35cf0350 RC |
300 | /** |
301 | * drm_modeset_lock_init - initialize lock | |
302 | * @lock: lock to init | |
303 | */ | |
304 | void drm_modeset_lock_init(struct drm_modeset_lock *lock) | |
305 | { | |
306 | ww_mutex_init(&lock->mutex, &crtc_ww_class); | |
307 | INIT_LIST_HEAD(&lock->head); | |
308 | } | |
309 | EXPORT_SYMBOL(drm_modeset_lock_init); | |
310 | ||
51fd371b RC |
311 | /** |
312 | * drm_modeset_lock - take modeset lock | |
313 | * @lock: lock to take | |
314 | * @ctx: acquire ctx | |
315 | * | |
316 | * If ctx is not NULL, then its ww acquire context is used and the | |
317 | * lock will be tracked by the context and can be released by calling | |
318 | * drm_modeset_drop_locks(). If -EDEADLK is returned, this means a | |
319 | * deadlock scenario has been detected and it is an error to attempt | |
320 | * to take any more locks without first calling drm_modeset_backoff(). | |
321 | */ | |
322 | int drm_modeset_lock(struct drm_modeset_lock *lock, | |
323 | struct drm_modeset_acquire_ctx *ctx) | |
324 | { | |
325 | if (ctx) | |
326 | return modeset_lock(lock, ctx, false, false); | |
327 | ||
328 | ww_mutex_lock(&lock->mutex, NULL); | |
329 | return 0; | |
330 | } | |
331 | EXPORT_SYMBOL(drm_modeset_lock); | |
332 | ||
333 | /** | |
334 | * drm_modeset_lock_interruptible - take modeset lock | |
335 | * @lock: lock to take | |
336 | * @ctx: acquire ctx | |
337 | * | |
338 | * Interruptible version of drm_modeset_lock() | |
339 | */ | |
340 | int drm_modeset_lock_interruptible(struct drm_modeset_lock *lock, | |
341 | struct drm_modeset_acquire_ctx *ctx) | |
342 | { | |
343 | if (ctx) | |
344 | return modeset_lock(lock, ctx, true, false); | |
345 | ||
346 | return ww_mutex_lock_interruptible(&lock->mutex, NULL); | |
347 | } | |
348 | EXPORT_SYMBOL(drm_modeset_lock_interruptible); | |
349 | ||
350 | /** | |
351 | * drm_modeset_unlock - drop modeset lock | |
352 | * @lock: lock to release | |
353 | */ | |
354 | void drm_modeset_unlock(struct drm_modeset_lock *lock) | |
355 | { | |
356 | list_del_init(&lock->head); | |
357 | ww_mutex_unlock(&lock->mutex); | |
358 | } | |
359 | EXPORT_SYMBOL(drm_modeset_unlock); | |
360 | ||
06eaae46 TR |
361 | /** |
362 | * drm_modeset_lock_all_ctx - take all modeset locks | |
363 | * @dev: DRM device | |
364 | * @ctx: lock acquisition context | |
365 | * | |
366 | * This function takes all modeset locks, suitable where a more fine-grained | |
367 | * scheme isn't (yet) implemented. | |
368 | * | |
d574528a | 369 | * Unlike drm_modeset_lock_all(), it doesn't take the &drm_mode_config.mutex |
06eaae46 TR |
370 | * since that lock isn't required for modeset state changes. Callers which |
371 | * need to grab that lock too need to do so outside of the acquire context | |
372 | * @ctx. | |
373 | * | |
374 | * Locks acquired with this function should be released by calling the | |
375 | * drm_modeset_drop_locks() function on @ctx. | |
376 | * | |
377 | * Returns: 0 on success or a negative error-code on failure. | |
378 | */ | |
379 | int drm_modeset_lock_all_ctx(struct drm_device *dev, | |
380 | struct drm_modeset_acquire_ctx *ctx) | |
51fd371b | 381 | { |
51fd371b | 382 | struct drm_crtc *crtc; |
4d02e2de | 383 | struct drm_plane *plane; |
06eaae46 TR |
384 | int ret; |
385 | ||
386 | ret = drm_modeset_lock(&dev->mode_config.connection_mutex, ctx); | |
387 | if (ret) | |
388 | return ret; | |
51fd371b | 389 | |
e4f62546 | 390 | drm_for_each_crtc(crtc, dev) { |
51fd371b RC |
391 | ret = drm_modeset_lock(&crtc->mutex, ctx); |
392 | if (ret) | |
393 | return ret; | |
394 | } | |
395 | ||
e4f62546 | 396 | drm_for_each_plane(plane, dev) { |
4d02e2de DV |
397 | ret = drm_modeset_lock(&plane->mutex, ctx); |
398 | if (ret) | |
399 | return ret; | |
400 | } | |
401 | ||
51fd371b RC |
402 | return 0; |
403 | } | |
06eaae46 | 404 | EXPORT_SYMBOL(drm_modeset_lock_all_ctx); |