Loading...
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 *
38 * For basic principles of ww_mutex, see: Documentation/locking/ww-mutex-design.txt
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 * ... do stuff ...
52 * drm_modeset_drop_locks(&ctx);
53 * drm_modeset_acquire_fini(&ctx);
54 */
55
56/**
57 * drm_modeset_lock_all - take all modeset locks
58 * @dev: DRM device
59 *
60 * This function takes all modeset locks, suitable where a more fine-grained
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.
70 */
71void drm_modeset_lock_all(struct drm_device *dev)
72{
73 struct drm_mode_config *config = &dev->mode_config;
74 struct drm_modeset_acquire_ctx *ctx;
75 int ret;
76
77 ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
78 if (WARN_ON(!ctx))
79 return;
80
81 mutex_lock(&config->mutex);
82
83 drm_modeset_acquire_init(ctx, 0);
84
85retry:
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 }
97
98 WARN_ON(config->acquire_ctx);
99
100 /*
101 * We hold the locks now, so it is safe to stash the acquisition
102 * context for drm_modeset_unlock_all().
103 */
104 config->acquire_ctx = ctx;
105
106 drm_warn_on_modeset_not_all_locked(dev);
107}
108EXPORT_SYMBOL(drm_modeset_lock_all);
109
110/**
111 * drm_modeset_unlock_all - drop all modeset locks
112 * @dev: DRM device
113 *
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.
123 */
124void 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}
140EXPORT_SYMBOL(drm_modeset_unlock_all);
141
142/**
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.
151 *
152 * Note that @plane can be NULL, e.g. when the cursor support hasn't yet been
153 * converted to universal planes yet.
154 */
155void drm_modeset_lock_crtc(struct drm_crtc *crtc,
156 struct drm_plane *plane)
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
167retry:
168 ret = drm_modeset_lock(&crtc->mutex, ctx);
169 if (ret)
170 goto fail;
171
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
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
193fail:
194 if (ret == -EDEADLK) {
195 drm_modeset_backoff(ctx);
196 goto retry;
197 }
198}
199EXPORT_SYMBOL(drm_modeset_lock_crtc);
200
201/**
202 * drm_modeset_legacy_acquire_ctx - find acquire ctx for legacy ioctls
203 * @crtc: drm crtc
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 */
210struct drm_modeset_acquire_ctx *
211drm_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}
220EXPORT_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 */
229void 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}
242EXPORT_SYMBOL(drm_modeset_unlock_crtc);
243
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 */
250void 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
258 drm_for_each_crtc(crtc, dev)
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}
264EXPORT_SYMBOL(drm_warn_on_modeset_not_all_locked);
265
266/**
267 * drm_modeset_acquire_init - initialize acquire context
268 * @ctx: the acquire context
269 * @flags: for future
270 */
271void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx,
272 uint32_t flags)
273{
274 memset(ctx, 0, sizeof(*ctx));
275 ww_acquire_init(&ctx->ww_ctx, &crtc_ww_class);
276 INIT_LIST_HEAD(&ctx->locked);
277}
278EXPORT_SYMBOL(drm_modeset_acquire_init);
279
280/**
281 * drm_modeset_acquire_fini - cleanup acquire context
282 * @ctx: the acquire context
283 */
284void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx)
285{
286 ww_acquire_fini(&ctx->ww_ctx);
287}
288EXPORT_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 */
296void 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}
308EXPORT_SYMBOL(drm_modeset_drop_locks);
309
310static 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
318 if (ctx->trylock_only) {
319 lockdep_assert_held(&ctx->ww_ctx);
320
321 if (!ww_mutex_trylock(&lock->mutex))
322 return -EBUSY;
323 else
324 return 0;
325 } else if (interruptible && slow) {
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
352static 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 */
375void drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx)
376{
377 modeset_backoff(ctx, false);
378}
379EXPORT_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 */
387int drm_modeset_backoff_interruptible(struct drm_modeset_acquire_ctx *ctx)
388{
389 return modeset_backoff(ctx, true);
390}
391EXPORT_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 */
404int 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}
413EXPORT_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 */
422int 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}
430EXPORT_SYMBOL(drm_modeset_lock_interruptible);
431
432/**
433 * drm_modeset_unlock - drop modeset lock
434 * @lock: lock to release
435 */
436void drm_modeset_unlock(struct drm_modeset_lock *lock)
437{
438 list_del_init(&lock->head);
439 ww_mutex_unlock(&lock->mutex);
440}
441EXPORT_SYMBOL(drm_modeset_unlock);
442
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 */
461int drm_modeset_lock_all_ctx(struct drm_device *dev,
462 struct drm_modeset_acquire_ctx *ctx)
463{
464 struct drm_crtc *crtc;
465 struct drm_plane *plane;
466 int ret;
467
468 ret = drm_modeset_lock(&dev->mode_config.connection_mutex, ctx);
469 if (ret)
470 return ret;
471
472 drm_for_each_crtc(crtc, dev) {
473 ret = drm_modeset_lock(&crtc->mutex, ctx);
474 if (ret)
475 return ret;
476 }
477
478 drm_for_each_plane(plane, dev) {
479 ret = drm_modeset_lock(&plane->mutex, ctx);
480 if (ret)
481 return ret;
482 }
483
484 return 0;
485}
486EXPORT_SYMBOL(drm_modeset_lock_all_ctx);
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 *
38 * For basic principles of &ww_mutex, see: Documentation/locking/ww-mutex-design.txt
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 * ... do stuff ...
52 * drm_modeset_drop_locks(&ctx);
53 * drm_modeset_acquire_fini(&ctx);
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.
61 */
62
63static DEFINE_WW_CLASS(crtc_ww_class);
64
65/**
66 * drm_modeset_lock_all - take all modeset locks
67 * @dev: DRM device
68 *
69 * This function takes all modeset locks, suitable where a more fine-grained
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
74 * stores it in the DRM device's ->mode_config. This facilitate conversion of
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.
79 */
80void drm_modeset_lock_all(struct drm_device *dev)
81{
82 struct drm_mode_config *config = &dev->mode_config;
83 struct drm_modeset_acquire_ctx *ctx;
84 int ret;
85
86 ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
87 if (WARN_ON(!ctx))
88 return;
89
90 mutex_lock(&config->mutex);
91
92 drm_modeset_acquire_init(ctx, 0);
93
94retry:
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 }
106
107 WARN_ON(config->acquire_ctx);
108
109 /*
110 * We hold the locks now, so it is safe to stash the acquisition
111 * context for drm_modeset_unlock_all().
112 */
113 config->acquire_ctx = ctx;
114
115 drm_warn_on_modeset_not_all_locked(dev);
116}
117EXPORT_SYMBOL(drm_modeset_lock_all);
118
119/**
120 * drm_modeset_unlock_all - drop all modeset locks
121 * @dev: DRM device
122 *
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
127 * in the DRM device's ->mode_config. This facilitates conversion of existing
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.
132 */
133void 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}
149EXPORT_SYMBOL(drm_modeset_unlock_all);
150
151/**
152 * drm_modeset_lock_crtc - lock crtc with hidden acquire ctx for a plane update
153 * @crtc: DRM CRTC
154 * @plane: DRM plane to be updated on @crtc
155 *
156 * This function locks the given crtc and plane (which should be either the
157 * primary or cursor plane) using a hidden acquire context. This is necessary so
158 * that drivers internally using the atomic interfaces can grab further locks
159 * with the lock acquire context.
160 *
161 * Note that @plane can be NULL, e.g. when the cursor support hasn't yet been
162 * converted to universal planes yet.
163 */
164void drm_modeset_lock_crtc(struct drm_crtc *crtc,
165 struct drm_plane *plane)
166{
167 struct drm_modeset_acquire_ctx *ctx;
168 int ret;
169
170 ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
171 if (WARN_ON(!ctx))
172 return;
173
174 drm_modeset_acquire_init(ctx, 0);
175
176retry:
177 ret = drm_modeset_lock(&crtc->mutex, ctx);
178 if (ret)
179 goto fail;
180
181 if (plane) {
182 ret = drm_modeset_lock(&plane->mutex, ctx);
183 if (ret)
184 goto fail;
185
186 if (plane->crtc) {
187 ret = drm_modeset_lock(&plane->crtc->mutex, ctx);
188 if (ret)
189 goto fail;
190 }
191 }
192
193 WARN_ON(crtc->acquire_ctx);
194
195 /* now we hold the locks, so now that it is safe, stash the
196 * ctx for drm_modeset_unlock_crtc():
197 */
198 crtc->acquire_ctx = ctx;
199
200 return;
201
202fail:
203 if (ret == -EDEADLK) {
204 drm_modeset_backoff(ctx);
205 goto retry;
206 }
207}
208EXPORT_SYMBOL(drm_modeset_lock_crtc);
209
210/**
211 * drm_modeset_legacy_acquire_ctx - find acquire ctx for legacy ioctls
212 * @crtc: drm crtc
213 *
214 * Legacy ioctl operations like cursor updates or page flips only have per-crtc
215 * locking, and store the acquire ctx in the corresponding crtc. All other
216 * legacy operations take all locks and use a global acquire context. This
217 * function grabs the right one.
218 */
219struct drm_modeset_acquire_ctx *
220drm_modeset_legacy_acquire_ctx(struct drm_crtc *crtc)
221{
222 if (crtc->acquire_ctx)
223 return crtc->acquire_ctx;
224
225 WARN_ON(!crtc->dev->mode_config.acquire_ctx);
226
227 return crtc->dev->mode_config.acquire_ctx;
228}
229EXPORT_SYMBOL(drm_modeset_legacy_acquire_ctx);
230
231/**
232 * drm_modeset_unlock_crtc - drop crtc lock
233 * @crtc: drm crtc
234 *
235 * This drops the crtc lock acquire with drm_modeset_lock_crtc() and all other
236 * locks acquired through the hidden context.
237 */
238void drm_modeset_unlock_crtc(struct drm_crtc *crtc)
239{
240 struct drm_modeset_acquire_ctx *ctx = crtc->acquire_ctx;
241
242 if (WARN_ON(!ctx))
243 return;
244
245 crtc->acquire_ctx = NULL;
246 drm_modeset_drop_locks(ctx);
247 drm_modeset_acquire_fini(ctx);
248
249 kfree(ctx);
250}
251EXPORT_SYMBOL(drm_modeset_unlock_crtc);
252
253/**
254 * drm_warn_on_modeset_not_all_locked - check that all modeset locks are locked
255 * @dev: device
256 *
257 * Useful as a debug assert.
258 */
259void drm_warn_on_modeset_not_all_locked(struct drm_device *dev)
260{
261 struct drm_crtc *crtc;
262
263 /* Locking is currently fubar in the panic handler. */
264 if (oops_in_progress)
265 return;
266
267 drm_for_each_crtc(crtc, dev)
268 WARN_ON(!drm_modeset_is_locked(&crtc->mutex));
269
270 WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
271 WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
272}
273EXPORT_SYMBOL(drm_warn_on_modeset_not_all_locked);
274
275/**
276 * drm_modeset_acquire_init - initialize acquire context
277 * @ctx: the acquire context
278 * @flags: for future
279 */
280void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx,
281 uint32_t flags)
282{
283 memset(ctx, 0, sizeof(*ctx));
284 ww_acquire_init(&ctx->ww_ctx, &crtc_ww_class);
285 INIT_LIST_HEAD(&ctx->locked);
286}
287EXPORT_SYMBOL(drm_modeset_acquire_init);
288
289/**
290 * drm_modeset_acquire_fini - cleanup acquire context
291 * @ctx: the acquire context
292 */
293void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx)
294{
295 ww_acquire_fini(&ctx->ww_ctx);
296}
297EXPORT_SYMBOL(drm_modeset_acquire_fini);
298
299/**
300 * drm_modeset_drop_locks - drop all locks
301 * @ctx: the acquire context
302 *
303 * Drop all locks currently held against this acquire context.
304 */
305void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx *ctx)
306{
307 WARN_ON(ctx->contended);
308 while (!list_empty(&ctx->locked)) {
309 struct drm_modeset_lock *lock;
310
311 lock = list_first_entry(&ctx->locked,
312 struct drm_modeset_lock, head);
313
314 drm_modeset_unlock(lock);
315 }
316}
317EXPORT_SYMBOL(drm_modeset_drop_locks);
318
319static inline int modeset_lock(struct drm_modeset_lock *lock,
320 struct drm_modeset_acquire_ctx *ctx,
321 bool interruptible, bool slow)
322{
323 int ret;
324
325 WARN_ON(ctx->contended);
326
327 if (ctx->trylock_only) {
328 lockdep_assert_held(&ctx->ww_ctx);
329
330 if (!ww_mutex_trylock(&lock->mutex))
331 return -EBUSY;
332 else
333 return 0;
334 } else if (interruptible && slow) {
335 ret = ww_mutex_lock_slow_interruptible(&lock->mutex, &ctx->ww_ctx);
336 } else if (interruptible) {
337 ret = ww_mutex_lock_interruptible(&lock->mutex, &ctx->ww_ctx);
338 } else if (slow) {
339 ww_mutex_lock_slow(&lock->mutex, &ctx->ww_ctx);
340 ret = 0;
341 } else {
342 ret = ww_mutex_lock(&lock->mutex, &ctx->ww_ctx);
343 }
344 if (!ret) {
345 WARN_ON(!list_empty(&lock->head));
346 list_add(&lock->head, &ctx->locked);
347 } else if (ret == -EALREADY) {
348 /* we already hold the lock.. this is fine. For atomic
349 * we will need to be able to drm_modeset_lock() things
350 * without having to keep track of what is already locked
351 * or not.
352 */
353 ret = 0;
354 } else if (ret == -EDEADLK) {
355 ctx->contended = lock;
356 }
357
358 return ret;
359}
360
361static int modeset_backoff(struct drm_modeset_acquire_ctx *ctx,
362 bool interruptible)
363{
364 struct drm_modeset_lock *contended = ctx->contended;
365
366 ctx->contended = NULL;
367
368 if (WARN_ON(!contended))
369 return 0;
370
371 drm_modeset_drop_locks(ctx);
372
373 return modeset_lock(contended, ctx, interruptible, true);
374}
375
376/**
377 * drm_modeset_backoff - deadlock avoidance backoff
378 * @ctx: the acquire context
379 *
380 * If deadlock is detected (ie. drm_modeset_lock() returns -EDEADLK),
381 * you must call this function to drop all currently held locks and
382 * block until the contended lock becomes available.
383 */
384void drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx)
385{
386 modeset_backoff(ctx, false);
387}
388EXPORT_SYMBOL(drm_modeset_backoff);
389
390/**
391 * drm_modeset_backoff_interruptible - deadlock avoidance backoff
392 * @ctx: the acquire context
393 *
394 * Interruptible version of drm_modeset_backoff()
395 */
396int drm_modeset_backoff_interruptible(struct drm_modeset_acquire_ctx *ctx)
397{
398 return modeset_backoff(ctx, true);
399}
400EXPORT_SYMBOL(drm_modeset_backoff_interruptible);
401
402/**
403 * drm_modeset_lock_init - initialize lock
404 * @lock: lock to init
405 */
406void drm_modeset_lock_init(struct drm_modeset_lock *lock)
407{
408 ww_mutex_init(&lock->mutex, &crtc_ww_class);
409 INIT_LIST_HEAD(&lock->head);
410}
411EXPORT_SYMBOL(drm_modeset_lock_init);
412
413/**
414 * drm_modeset_lock - take modeset lock
415 * @lock: lock to take
416 * @ctx: acquire ctx
417 *
418 * If ctx is not NULL, then its ww acquire context is used and the
419 * lock will be tracked by the context and can be released by calling
420 * drm_modeset_drop_locks(). If -EDEADLK is returned, this means a
421 * deadlock scenario has been detected and it is an error to attempt
422 * to take any more locks without first calling drm_modeset_backoff().
423 */
424int drm_modeset_lock(struct drm_modeset_lock *lock,
425 struct drm_modeset_acquire_ctx *ctx)
426{
427 if (ctx)
428 return modeset_lock(lock, ctx, false, false);
429
430 ww_mutex_lock(&lock->mutex, NULL);
431 return 0;
432}
433EXPORT_SYMBOL(drm_modeset_lock);
434
435/**
436 * drm_modeset_lock_interruptible - take modeset lock
437 * @lock: lock to take
438 * @ctx: acquire ctx
439 *
440 * Interruptible version of drm_modeset_lock()
441 */
442int drm_modeset_lock_interruptible(struct drm_modeset_lock *lock,
443 struct drm_modeset_acquire_ctx *ctx)
444{
445 if (ctx)
446 return modeset_lock(lock, ctx, true, false);
447
448 return ww_mutex_lock_interruptible(&lock->mutex, NULL);
449}
450EXPORT_SYMBOL(drm_modeset_lock_interruptible);
451
452/**
453 * drm_modeset_unlock - drop modeset lock
454 * @lock: lock to release
455 */
456void drm_modeset_unlock(struct drm_modeset_lock *lock)
457{
458 list_del_init(&lock->head);
459 ww_mutex_unlock(&lock->mutex);
460}
461EXPORT_SYMBOL(drm_modeset_unlock);
462
463/**
464 * drm_modeset_lock_all_ctx - take all modeset locks
465 * @dev: DRM device
466 * @ctx: lock acquisition context
467 *
468 * This function takes all modeset locks, suitable where a more fine-grained
469 * scheme isn't (yet) implemented.
470 *
471 * Unlike drm_modeset_lock_all(), it doesn't take the dev->mode_config.mutex
472 * since that lock isn't required for modeset state changes. Callers which
473 * need to grab that lock too need to do so outside of the acquire context
474 * @ctx.
475 *
476 * Locks acquired with this function should be released by calling the
477 * drm_modeset_drop_locks() function on @ctx.
478 *
479 * Returns: 0 on success or a negative error-code on failure.
480 */
481int drm_modeset_lock_all_ctx(struct drm_device *dev,
482 struct drm_modeset_acquire_ctx *ctx)
483{
484 struct drm_crtc *crtc;
485 struct drm_plane *plane;
486 int ret;
487
488 ret = drm_modeset_lock(&dev->mode_config.connection_mutex, ctx);
489 if (ret)
490 return ret;
491
492 drm_for_each_crtc(crtc, dev) {
493 ret = drm_modeset_lock(&crtc->mutex, ctx);
494 if (ret)
495 return ret;
496 }
497
498 drm_for_each_plane(plane, dev) {
499 ret = drm_modeset_lock(&plane->mutex, ctx);
500 if (ret)
501 return ret;
502 }
503
504 return 0;
505}
506EXPORT_SYMBOL(drm_modeset_lock_all_ctx);