blob: 51cc47d827d82f09f1ed9d0e4200e299b4fa628c [file] [log] [blame]
Rob Clark51fd3712013-11-19 12:10:12 -05001/*
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 *
Davidlohr Bueso214e0ae2014-07-30 13:41:55 -070038 * For basic principles of ww_mutex, see: Documentation/locking/ww-mutex-design.txt
Rob Clark51fd3712013-11-19 12:10:12 -050039 *
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
59/**
Daniel Vettercb597bb2014-07-27 19:09:33 +020060 * __drm_modeset_lock_all - internal helper to grab all modeset locks
61 * @dev: DRM device
62 * @trylock: trylock mode for atomic contexts
Daniel Vettera6a8bb82014-07-25 17:47:18 +020063 *
Daniel Vettercb597bb2014-07-27 19:09:33 +020064 * This is a special version of drm_modeset_lock_all() which can also be used in
65 * atomic contexts. Then @trylock must be set to true.
66 *
67 * Returns:
68 * 0 on success or negative error code on failure.
Daniel Vettera6a8bb82014-07-25 17:47:18 +020069 */
Daniel Vettercb597bb2014-07-27 19:09:33 +020070int __drm_modeset_lock_all(struct drm_device *dev,
71 bool trylock)
Daniel Vettera6a8bb82014-07-25 17:47:18 +020072{
73 struct drm_mode_config *config = &dev->mode_config;
74 struct drm_modeset_acquire_ctx *ctx;
75 int ret;
76
Daniel Vettercb597bb2014-07-27 19:09:33 +020077 ctx = kzalloc(sizeof(*ctx),
78 trylock ? GFP_ATOMIC : GFP_KERNEL);
79 if (!ctx)
80 return -ENOMEM;
Daniel Vettera6a8bb82014-07-25 17:47:18 +020081
Daniel Vettercb597bb2014-07-27 19:09:33 +020082 if (trylock) {
83 if (!mutex_trylock(&config->mutex))
84 return -EBUSY;
85 } else {
86 mutex_lock(&config->mutex);
87 }
Daniel Vettera6a8bb82014-07-25 17:47:18 +020088
89 drm_modeset_acquire_init(ctx, 0);
Daniel Vettercb597bb2014-07-27 19:09:33 +020090 ctx->trylock_only = trylock;
Daniel Vettera6a8bb82014-07-25 17:47:18 +020091
92retry:
93 ret = drm_modeset_lock(&config->connection_mutex, ctx);
94 if (ret)
95 goto fail;
96 ret = drm_modeset_lock_all_crtcs(dev, ctx);
97 if (ret)
98 goto fail;
99
100 WARN_ON(config->acquire_ctx);
101
102 /* now we hold the locks, so now that it is safe, stash the
103 * ctx for drm_modeset_unlock_all():
104 */
105 config->acquire_ctx = ctx;
106
107 drm_warn_on_modeset_not_all_locked(dev);
108
Daniel Vettercb597bb2014-07-27 19:09:33 +0200109 return 0;
Daniel Vettera6a8bb82014-07-25 17:47:18 +0200110
111fail:
112 if (ret == -EDEADLK) {
113 drm_modeset_backoff(ctx);
114 goto retry;
115 }
Daniel Vettercb597bb2014-07-27 19:09:33 +0200116
117 return ret;
118}
119EXPORT_SYMBOL(__drm_modeset_lock_all);
120
121/**
122 * drm_modeset_lock_all - take all modeset locks
123 * @dev: drm device
124 *
125 * This function takes all modeset locks, suitable where a more fine-grained
126 * scheme isn't (yet) implemented. Locks must be dropped with
127 * drm_modeset_unlock_all.
128 */
129void drm_modeset_lock_all(struct drm_device *dev)
130{
131 WARN_ON(__drm_modeset_lock_all(dev, false) != 0);
Daniel Vettera6a8bb82014-07-25 17:47:18 +0200132}
133EXPORT_SYMBOL(drm_modeset_lock_all);
134
135/**
136 * drm_modeset_unlock_all - drop all modeset locks
137 * @dev: device
138 *
139 * This function drop all modeset locks taken by drm_modeset_lock_all.
140 */
141void drm_modeset_unlock_all(struct drm_device *dev)
142{
143 struct drm_mode_config *config = &dev->mode_config;
144 struct drm_modeset_acquire_ctx *ctx = config->acquire_ctx;
145
146 if (WARN_ON(!ctx))
147 return;
148
149 config->acquire_ctx = NULL;
150 drm_modeset_drop_locks(ctx);
151 drm_modeset_acquire_fini(ctx);
152
153 kfree(ctx);
154
155 mutex_unlock(&dev->mode_config.mutex);
156}
157EXPORT_SYMBOL(drm_modeset_unlock_all);
158
159/**
Daniel Vetter4d02e2d2014-11-11 10:12:00 +0100160 * drm_modeset_lock_crtc - lock crtc with hidden acquire ctx for a plane update
161 * @crtc: DRM CRTC
162 * @plane: DRM plane to be updated on @crtc
Daniel Vetterd059f652014-07-25 18:07:40 +0200163 *
Daniel Vetter4d02e2d2014-11-11 10:12:00 +0100164 * This function locks the given crtc and plane (which should be either the
165 * primary or cursor plane) using a hidden acquire context. This is necessary so
166 * that drivers internally using the atomic interfaces can grab further locks
167 * with the lock acquire context.
168 *
169 * Note that @plane can be NULL, e.g. when the cursor support hasn't yet been
170 * converted to universal planes yet.
Daniel Vetterd059f652014-07-25 18:07:40 +0200171 */
Daniel Vetter4d02e2d2014-11-11 10:12:00 +0100172void drm_modeset_lock_crtc(struct drm_crtc *crtc,
173 struct drm_plane *plane)
Daniel Vetterd059f652014-07-25 18:07:40 +0200174{
175 struct drm_modeset_acquire_ctx *ctx;
176 int ret;
177
178 ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
179 if (WARN_ON(!ctx))
180 return;
181
182 drm_modeset_acquire_init(ctx, 0);
183
184retry:
185 ret = drm_modeset_lock(&crtc->mutex, ctx);
186 if (ret)
187 goto fail;
188
Daniel Vetter4d02e2d2014-11-11 10:12:00 +0100189 if (plane) {
190 ret = drm_modeset_lock(&plane->mutex, ctx);
191 if (ret)
192 goto fail;
193
194 if (plane->crtc) {
195 ret = drm_modeset_lock(&plane->crtc->mutex, ctx);
196 if (ret)
197 goto fail;
198 }
199 }
200
Daniel Vetterd059f652014-07-25 18:07:40 +0200201 WARN_ON(crtc->acquire_ctx);
202
203 /* now we hold the locks, so now that it is safe, stash the
204 * ctx for drm_modeset_unlock_crtc():
205 */
206 crtc->acquire_ctx = ctx;
207
208 return;
209
210fail:
211 if (ret == -EDEADLK) {
212 drm_modeset_backoff(ctx);
213 goto retry;
214 }
215}
216EXPORT_SYMBOL(drm_modeset_lock_crtc);
217
218/**
219 * drm_modeset_legacy_acquire_ctx - find acquire ctx for legacy ioctls
Daniel Vetter295ee852014-07-30 14:23:44 +0200220 * @crtc: drm crtc
Daniel Vetterd059f652014-07-25 18:07:40 +0200221 *
222 * Legacy ioctl operations like cursor updates or page flips only have per-crtc
223 * locking, and store the acquire ctx in the corresponding crtc. All other
224 * legacy operations take all locks and use a global acquire context. This
225 * function grabs the right one.
226 */
227struct drm_modeset_acquire_ctx *
228drm_modeset_legacy_acquire_ctx(struct drm_crtc *crtc)
229{
230 if (crtc->acquire_ctx)
231 return crtc->acquire_ctx;
232
233 WARN_ON(!crtc->dev->mode_config.acquire_ctx);
234
235 return crtc->dev->mode_config.acquire_ctx;
236}
237EXPORT_SYMBOL(drm_modeset_legacy_acquire_ctx);
238
239/**
240 * drm_modeset_unlock_crtc - drop crtc lock
241 * @crtc: drm crtc
242 *
243 * This drops the crtc lock acquire with drm_modeset_lock_crtc() and all other
244 * locks acquired through the hidden context.
245 */
246void drm_modeset_unlock_crtc(struct drm_crtc *crtc)
247{
248 struct drm_modeset_acquire_ctx *ctx = crtc->acquire_ctx;
249
250 if (WARN_ON(!ctx))
251 return;
252
253 crtc->acquire_ctx = NULL;
254 drm_modeset_drop_locks(ctx);
255 drm_modeset_acquire_fini(ctx);
256
257 kfree(ctx);
258}
259EXPORT_SYMBOL(drm_modeset_unlock_crtc);
260
261/**
Daniel Vettera6a8bb82014-07-25 17:47:18 +0200262 * drm_warn_on_modeset_not_all_locked - check that all modeset locks are locked
263 * @dev: device
264 *
265 * Useful as a debug assert.
266 */
267void drm_warn_on_modeset_not_all_locked(struct drm_device *dev)
268{
269 struct drm_crtc *crtc;
270
271 /* Locking is currently fubar in the panic handler. */
272 if (oops_in_progress)
273 return;
274
275 list_for_each_entry(crtc, &dev->mode_config.crtc_list, head)
276 WARN_ON(!drm_modeset_is_locked(&crtc->mutex));
277
278 WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
279 WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
280}
281EXPORT_SYMBOL(drm_warn_on_modeset_not_all_locked);
282
283/**
Rob Clark51fd3712013-11-19 12:10:12 -0500284 * drm_modeset_acquire_init - initialize acquire context
285 * @ctx: the acquire context
286 * @flags: for future
287 */
288void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx,
289 uint32_t flags)
290{
Rob Clarkfb549182014-06-07 10:55:39 -0400291 memset(ctx, 0, sizeof(*ctx));
Rob Clark51fd3712013-11-19 12:10:12 -0500292 ww_acquire_init(&ctx->ww_ctx, &crtc_ww_class);
293 INIT_LIST_HEAD(&ctx->locked);
294}
295EXPORT_SYMBOL(drm_modeset_acquire_init);
296
297/**
298 * drm_modeset_acquire_fini - cleanup acquire context
299 * @ctx: the acquire context
300 */
301void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx)
302{
303 ww_acquire_fini(&ctx->ww_ctx);
304}
305EXPORT_SYMBOL(drm_modeset_acquire_fini);
306
307/**
308 * drm_modeset_drop_locks - drop all locks
309 * @ctx: the acquire context
310 *
311 * Drop all locks currently held against this acquire context.
312 */
313void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx *ctx)
314{
315 WARN_ON(ctx->contended);
316 while (!list_empty(&ctx->locked)) {
317 struct drm_modeset_lock *lock;
318
319 lock = list_first_entry(&ctx->locked,
320 struct drm_modeset_lock, head);
321
322 drm_modeset_unlock(lock);
323 }
324}
325EXPORT_SYMBOL(drm_modeset_drop_locks);
326
327static inline int modeset_lock(struct drm_modeset_lock *lock,
328 struct drm_modeset_acquire_ctx *ctx,
329 bool interruptible, bool slow)
330{
331 int ret;
332
333 WARN_ON(ctx->contended);
334
Daniel Vettercb597bb2014-07-27 19:09:33 +0200335 if (ctx->trylock_only) {
336 if (!ww_mutex_trylock(&lock->mutex))
337 return -EBUSY;
338 else
339 return 0;
340 } else if (interruptible && slow) {
Rob Clark51fd3712013-11-19 12:10:12 -0500341 ret = ww_mutex_lock_slow_interruptible(&lock->mutex, &ctx->ww_ctx);
342 } else if (interruptible) {
343 ret = ww_mutex_lock_interruptible(&lock->mutex, &ctx->ww_ctx);
344 } else if (slow) {
345 ww_mutex_lock_slow(&lock->mutex, &ctx->ww_ctx);
346 ret = 0;
347 } else {
348 ret = ww_mutex_lock(&lock->mutex, &ctx->ww_ctx);
349 }
350 if (!ret) {
351 WARN_ON(!list_empty(&lock->head));
352 list_add(&lock->head, &ctx->locked);
353 } else if (ret == -EALREADY) {
354 /* we already hold the lock.. this is fine. For atomic
355 * we will need to be able to drm_modeset_lock() things
356 * without having to keep track of what is already locked
357 * or not.
358 */
359 ret = 0;
360 } else if (ret == -EDEADLK) {
361 ctx->contended = lock;
362 }
363
364 return ret;
365}
366
367static int modeset_backoff(struct drm_modeset_acquire_ctx *ctx,
368 bool interruptible)
369{
370 struct drm_modeset_lock *contended = ctx->contended;
371
372 ctx->contended = NULL;
373
374 if (WARN_ON(!contended))
375 return 0;
376
377 drm_modeset_drop_locks(ctx);
378
379 return modeset_lock(contended, ctx, interruptible, true);
380}
381
382/**
383 * drm_modeset_backoff - deadlock avoidance backoff
384 * @ctx: the acquire context
385 *
386 * If deadlock is detected (ie. drm_modeset_lock() returns -EDEADLK),
387 * you must call this function to drop all currently held locks and
388 * block until the contended lock becomes available.
389 */
390void drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx)
391{
392 modeset_backoff(ctx, false);
393}
394EXPORT_SYMBOL(drm_modeset_backoff);
395
396/**
397 * drm_modeset_backoff_interruptible - deadlock avoidance backoff
398 * @ctx: the acquire context
399 *
400 * Interruptible version of drm_modeset_backoff()
401 */
402int drm_modeset_backoff_interruptible(struct drm_modeset_acquire_ctx *ctx)
403{
404 return modeset_backoff(ctx, true);
405}
406EXPORT_SYMBOL(drm_modeset_backoff_interruptible);
407
408/**
409 * drm_modeset_lock - take modeset lock
410 * @lock: lock to take
411 * @ctx: acquire ctx
412 *
413 * If ctx is not NULL, then its ww acquire context is used and the
414 * lock will be tracked by the context and can be released by calling
415 * drm_modeset_drop_locks(). If -EDEADLK is returned, this means a
416 * deadlock scenario has been detected and it is an error to attempt
417 * to take any more locks without first calling drm_modeset_backoff().
418 */
419int drm_modeset_lock(struct drm_modeset_lock *lock,
420 struct drm_modeset_acquire_ctx *ctx)
421{
422 if (ctx)
423 return modeset_lock(lock, ctx, false, false);
424
425 ww_mutex_lock(&lock->mutex, NULL);
426 return 0;
427}
428EXPORT_SYMBOL(drm_modeset_lock);
429
430/**
431 * drm_modeset_lock_interruptible - take modeset lock
432 * @lock: lock to take
433 * @ctx: acquire ctx
434 *
435 * Interruptible version of drm_modeset_lock()
436 */
437int drm_modeset_lock_interruptible(struct drm_modeset_lock *lock,
438 struct drm_modeset_acquire_ctx *ctx)
439{
440 if (ctx)
441 return modeset_lock(lock, ctx, true, false);
442
443 return ww_mutex_lock_interruptible(&lock->mutex, NULL);
444}
445EXPORT_SYMBOL(drm_modeset_lock_interruptible);
446
447/**
448 * drm_modeset_unlock - drop modeset lock
449 * @lock: lock to release
450 */
451void drm_modeset_unlock(struct drm_modeset_lock *lock)
452{
453 list_del_init(&lock->head);
454 ww_mutex_unlock(&lock->mutex);
455}
456EXPORT_SYMBOL(drm_modeset_unlock);
457
Daniel Vetter4d02e2d2014-11-11 10:12:00 +0100458/* In some legacy codepaths it's convenient to just grab all the crtc and plane
459 * related locks. */
Rob Clark51fd3712013-11-19 12:10:12 -0500460int drm_modeset_lock_all_crtcs(struct drm_device *dev,
461 struct drm_modeset_acquire_ctx *ctx)
462{
463 struct drm_mode_config *config = &dev->mode_config;
464 struct drm_crtc *crtc;
Daniel Vetter4d02e2d2014-11-11 10:12:00 +0100465 struct drm_plane *plane;
Rob Clark51fd3712013-11-19 12:10:12 -0500466 int ret = 0;
467
468 list_for_each_entry(crtc, &config->crtc_list, head) {
469 ret = drm_modeset_lock(&crtc->mutex, ctx);
470 if (ret)
471 return ret;
472 }
473
Daniel Vetter4d02e2d2014-11-11 10:12:00 +0100474 list_for_each_entry(plane, &config->plane_list, head) {
475 ret = drm_modeset_lock(&plane->mutex, ctx);
476 if (ret)
477 return ret;
478 }
479
Rob Clark51fd3712013-11-19 12:10:12 -0500480 return 0;
481}
482EXPORT_SYMBOL(drm_modeset_lock_all_crtcs);