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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/drm_atomic.h>
25#include <drm/drm_crtc.h>
26#include <drm/drm_device.h>
27#include <drm/drm_modeset_lock.h>
28
29/**
30 * DOC: kms locking
31 *
32 * As KMS moves toward more fine grained locking, and atomic ioctl where
33 * userspace can indirectly control locking order, it becomes necessary
34 * to use &ww_mutex and acquire-contexts to avoid deadlocks. But because
35 * the locking is more distributed around the driver code, we want a bit
36 * of extra utility/tracking out of our acquire-ctx. This is provided
37 * by &struct drm_modeset_lock and &struct drm_modeset_acquire_ctx.
38 *
39 * For basic principles of &ww_mutex, see: Documentation/locking/ww-mutex-design.rst
40 *
41 * The basic usage pattern is to::
42 *
43 * drm_modeset_acquire_init(ctx, DRM_MODESET_ACQUIRE_INTERRUPTIBLE)
44 * retry:
45 * foreach (lock in random_ordered_set_of_locks) {
46 * ret = drm_modeset_lock(lock, ctx)
47 * if (ret == -EDEADLK) {
48 * ret = drm_modeset_backoff(ctx);
49 * if (!ret)
50 * goto retry;
51 * }
52 * if (ret)
53 * goto out;
54 * }
55 * ... do stuff ...
56 * out:
57 * drm_modeset_drop_locks(ctx);
58 * drm_modeset_acquire_fini(ctx);
59 *
60 * For convenience this control flow is implemented in
61 * DRM_MODESET_LOCK_ALL_BEGIN() and DRM_MODESET_LOCK_ALL_END() for the case
62 * where all modeset locks need to be taken through drm_modeset_lock_all_ctx().
63 *
64 * If all that is needed is a single modeset lock, then the &struct
65 * drm_modeset_acquire_ctx is not needed and the locking can be simplified
66 * by passing a NULL instead of ctx in the drm_modeset_lock() call or
67 * calling drm_modeset_lock_single_interruptible(). To unlock afterwards
68 * call drm_modeset_unlock().
69 *
70 * On top of these per-object locks using &ww_mutex there's also an overall
71 * &drm_mode_config.mutex, for protecting everything else. Mostly this means
72 * probe state of connectors, and preventing hotplug add/removal of connectors.
73 *
74 * Finally there's a bunch of dedicated locks to protect drm core internal
75 * lists and lookup data structures.
76 */
77
78static DEFINE_WW_CLASS(crtc_ww_class);
79
80/**
81 * drm_modeset_lock_all - take all modeset locks
82 * @dev: DRM device
83 *
84 * This function takes all modeset locks, suitable where a more fine-grained
85 * scheme isn't (yet) implemented. Locks must be dropped by calling the
86 * drm_modeset_unlock_all() function.
87 *
88 * This function is deprecated. It allocates a lock acquisition context and
89 * stores it in &drm_device.mode_config. This facilitate conversion of
90 * existing code because it removes the need to manually deal with the
91 * acquisition context, but it is also brittle because the context is global
92 * and care must be taken not to nest calls. New code should use the
93 * drm_modeset_lock_all_ctx() function and pass in the context explicitly.
94 */
95void drm_modeset_lock_all(struct drm_device *dev)
96{
97 struct drm_mode_config *config = &dev->mode_config;
98 struct drm_modeset_acquire_ctx *ctx;
99 int ret;
100
101 ctx = kzalloc(sizeof(*ctx), GFP_KERNEL | __GFP_NOFAIL);
102 if (WARN_ON(!ctx))
103 return;
104
105 mutex_lock(&config->mutex);
106
107 drm_modeset_acquire_init(ctx, 0);
108
109retry:
110 ret = drm_modeset_lock_all_ctx(dev, ctx);
111 if (ret < 0) {
112 if (ret == -EDEADLK) {
113 drm_modeset_backoff(ctx);
114 goto retry;
115 }
116
117 drm_modeset_acquire_fini(ctx);
118 kfree(ctx);
119 return;
120 }
121 ww_acquire_done(&ctx->ww_ctx);
122
123 WARN_ON(config->acquire_ctx);
124
125 /*
126 * We hold the locks now, so it is safe to stash the acquisition
127 * context for drm_modeset_unlock_all().
128 */
129 config->acquire_ctx = ctx;
130
131 drm_warn_on_modeset_not_all_locked(dev);
132}
133EXPORT_SYMBOL(drm_modeset_lock_all);
134
135/**
136 * drm_modeset_unlock_all - drop all modeset locks
137 * @dev: DRM device
138 *
139 * This function drops all modeset locks taken by a previous call to the
140 * drm_modeset_lock_all() function.
141 *
142 * This function is deprecated. It uses the lock acquisition context stored
143 * in &drm_device.mode_config. This facilitates conversion of existing
144 * code because it removes the need to manually deal with the acquisition
145 * context, but it is also brittle because the context is global and care must
146 * be taken not to nest calls. New code should pass the acquisition context
147 * directly to the drm_modeset_drop_locks() function.
148 */
149void drm_modeset_unlock_all(struct drm_device *dev)
150{
151 struct drm_mode_config *config = &dev->mode_config;
152 struct drm_modeset_acquire_ctx *ctx = config->acquire_ctx;
153
154 if (WARN_ON(!ctx))
155 return;
156
157 config->acquire_ctx = NULL;
158 drm_modeset_drop_locks(ctx);
159 drm_modeset_acquire_fini(ctx);
160
161 kfree(ctx);
162
163 mutex_unlock(&dev->mode_config.mutex);
164}
165EXPORT_SYMBOL(drm_modeset_unlock_all);
166
167/**
168 * drm_warn_on_modeset_not_all_locked - check that all modeset locks are locked
169 * @dev: device
170 *
171 * Useful as a debug assert.
172 */
173void drm_warn_on_modeset_not_all_locked(struct drm_device *dev)
174{
175 struct drm_crtc *crtc;
176
177 /* Locking is currently fubar in the panic handler. */
178 if (oops_in_progress)
179 return;
180
181 drm_for_each_crtc(crtc, dev)
182 WARN_ON(!drm_modeset_is_locked(&crtc->mutex));
183
184 WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
185 WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
186}
187EXPORT_SYMBOL(drm_warn_on_modeset_not_all_locked);
188
189/**
190 * drm_modeset_acquire_init - initialize acquire context
191 * @ctx: the acquire context
192 * @flags: 0 or %DRM_MODESET_ACQUIRE_INTERRUPTIBLE
193 *
194 * When passing %DRM_MODESET_ACQUIRE_INTERRUPTIBLE to @flags,
195 * all calls to drm_modeset_lock() will perform an interruptible
196 * wait.
197 */
198void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx,
199 uint32_t flags)
200{
201 memset(ctx, 0, sizeof(*ctx));
202 ww_acquire_init(&ctx->ww_ctx, &crtc_ww_class);
203 INIT_LIST_HEAD(&ctx->locked);
204
205 if (flags & DRM_MODESET_ACQUIRE_INTERRUPTIBLE)
206 ctx->interruptible = true;
207}
208EXPORT_SYMBOL(drm_modeset_acquire_init);
209
210/**
211 * drm_modeset_acquire_fini - cleanup acquire context
212 * @ctx: the acquire context
213 */
214void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx)
215{
216 ww_acquire_fini(&ctx->ww_ctx);
217}
218EXPORT_SYMBOL(drm_modeset_acquire_fini);
219
220/**
221 * drm_modeset_drop_locks - drop all locks
222 * @ctx: the acquire context
223 *
224 * Drop all locks currently held against this acquire context.
225 */
226void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx *ctx)
227{
228 WARN_ON(ctx->contended);
229 while (!list_empty(&ctx->locked)) {
230 struct drm_modeset_lock *lock;
231
232 lock = list_first_entry(&ctx->locked,
233 struct drm_modeset_lock, head);
234
235 drm_modeset_unlock(lock);
236 }
237}
238EXPORT_SYMBOL(drm_modeset_drop_locks);
239
240static inline int modeset_lock(struct drm_modeset_lock *lock,
241 struct drm_modeset_acquire_ctx *ctx,
242 bool interruptible, bool slow)
243{
244 int ret;
245
246 WARN_ON(ctx->contended);
247
248 if (ctx->trylock_only) {
249 lockdep_assert_held(&ctx->ww_ctx);
250
251 if (!ww_mutex_trylock(&lock->mutex))
252 return -EBUSY;
253 else
254 return 0;
255 } else if (interruptible && slow) {
256 ret = ww_mutex_lock_slow_interruptible(&lock->mutex, &ctx->ww_ctx);
257 } else if (interruptible) {
258 ret = ww_mutex_lock_interruptible(&lock->mutex, &ctx->ww_ctx);
259 } else if (slow) {
260 ww_mutex_lock_slow(&lock->mutex, &ctx->ww_ctx);
261 ret = 0;
262 } else {
263 ret = ww_mutex_lock(&lock->mutex, &ctx->ww_ctx);
264 }
265 if (!ret) {
266 WARN_ON(!list_empty(&lock->head));
267 list_add(&lock->head, &ctx->locked);
268 } else if (ret == -EALREADY) {
269 /* we already hold the lock.. this is fine. For atomic
270 * we will need to be able to drm_modeset_lock() things
271 * without having to keep track of what is already locked
272 * or not.
273 */
274 ret = 0;
275 } else if (ret == -EDEADLK) {
276 ctx->contended = lock;
277 }
278
279 return ret;
280}
281
282/**
283 * drm_modeset_backoff - deadlock avoidance backoff
284 * @ctx: the acquire context
285 *
286 * If deadlock is detected (ie. drm_modeset_lock() returns -EDEADLK),
287 * you must call this function to drop all currently held locks and
288 * block until the contended lock becomes available.
289 *
290 * This function returns 0 on success, or -ERESTARTSYS if this context
291 * is initialized with %DRM_MODESET_ACQUIRE_INTERRUPTIBLE and the
292 * wait has been interrupted.
293 */
294int drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx)
295{
296 struct drm_modeset_lock *contended = ctx->contended;
297
298 ctx->contended = NULL;
299
300 if (WARN_ON(!contended))
301 return 0;
302
303 drm_modeset_drop_locks(ctx);
304
305 return modeset_lock(contended, ctx, ctx->interruptible, true);
306}
307EXPORT_SYMBOL(drm_modeset_backoff);
308
309/**
310 * drm_modeset_lock_init - initialize lock
311 * @lock: lock to init
312 */
313void drm_modeset_lock_init(struct drm_modeset_lock *lock)
314{
315 ww_mutex_init(&lock->mutex, &crtc_ww_class);
316 INIT_LIST_HEAD(&lock->head);
317}
318EXPORT_SYMBOL(drm_modeset_lock_init);
319
320/**
321 * drm_modeset_lock - take modeset lock
322 * @lock: lock to take
323 * @ctx: acquire ctx
324 *
325 * If @ctx is not NULL, then its ww acquire context is used and the
326 * lock will be tracked by the context and can be released by calling
327 * drm_modeset_drop_locks(). If -EDEADLK is returned, this means a
328 * deadlock scenario has been detected and it is an error to attempt
329 * to take any more locks without first calling drm_modeset_backoff().
330 *
331 * If the @ctx is not NULL and initialized with
332 * %DRM_MODESET_ACQUIRE_INTERRUPTIBLE, this function will fail with
333 * -ERESTARTSYS when interrupted.
334 *
335 * If @ctx is NULL then the function call behaves like a normal,
336 * uninterruptible non-nesting mutex_lock() call.
337 */
338int drm_modeset_lock(struct drm_modeset_lock *lock,
339 struct drm_modeset_acquire_ctx *ctx)
340{
341 if (ctx)
342 return modeset_lock(lock, ctx, ctx->interruptible, false);
343
344 ww_mutex_lock(&lock->mutex, NULL);
345 return 0;
346}
347EXPORT_SYMBOL(drm_modeset_lock);
348
349/**
350 * drm_modeset_lock_single_interruptible - take a single modeset lock
351 * @lock: lock to take
352 *
353 * This function behaves as drm_modeset_lock() with a NULL context,
354 * but performs interruptible waits.
355 *
356 * This function returns 0 on success, or -ERESTARTSYS when interrupted.
357 */
358int drm_modeset_lock_single_interruptible(struct drm_modeset_lock *lock)
359{
360 return ww_mutex_lock_interruptible(&lock->mutex, NULL);
361}
362EXPORT_SYMBOL(drm_modeset_lock_single_interruptible);
363
364/**
365 * drm_modeset_unlock - drop modeset lock
366 * @lock: lock to release
367 */
368void drm_modeset_unlock(struct drm_modeset_lock *lock)
369{
370 list_del_init(&lock->head);
371 ww_mutex_unlock(&lock->mutex);
372}
373EXPORT_SYMBOL(drm_modeset_unlock);
374
375/**
376 * drm_modeset_lock_all_ctx - take all modeset locks
377 * @dev: DRM device
378 * @ctx: lock acquisition context
379 *
380 * This function takes all modeset locks, suitable where a more fine-grained
381 * scheme isn't (yet) implemented.
382 *
383 * Unlike drm_modeset_lock_all(), it doesn't take the &drm_mode_config.mutex
384 * since that lock isn't required for modeset state changes. Callers which
385 * need to grab that lock too need to do so outside of the acquire context
386 * @ctx.
387 *
388 * Locks acquired with this function should be released by calling the
389 * drm_modeset_drop_locks() function on @ctx.
390 *
391 * See also: DRM_MODESET_LOCK_ALL_BEGIN() and DRM_MODESET_LOCK_ALL_END()
392 *
393 * Returns: 0 on success or a negative error-code on failure.
394 */
395int drm_modeset_lock_all_ctx(struct drm_device *dev,
396 struct drm_modeset_acquire_ctx *ctx)
397{
398 struct drm_private_obj *privobj;
399 struct drm_crtc *crtc;
400 struct drm_plane *plane;
401 int ret;
402
403 ret = drm_modeset_lock(&dev->mode_config.connection_mutex, ctx);
404 if (ret)
405 return ret;
406
407 drm_for_each_crtc(crtc, dev) {
408 ret = drm_modeset_lock(&crtc->mutex, ctx);
409 if (ret)
410 return ret;
411 }
412
413 drm_for_each_plane(plane, dev) {
414 ret = drm_modeset_lock(&plane->mutex, ctx);
415 if (ret)
416 return ret;
417 }
418
419 drm_for_each_privobj(privobj, dev) {
420 ret = drm_modeset_lock(&privobj->lock, ctx);
421 if (ret)
422 return ret;
423 }
424
425 return 0;
426}
427EXPORT_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 &struct drm_modeset_lock and &struct 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, DRM_MODESET_ACQUIRE_INTERRUPTIBLE)
43 * retry:
44 * foreach (lock in random_ordered_set_of_locks) {
45 * ret = drm_modeset_lock(lock, ctx)
46 * if (ret == -EDEADLK) {
47 * ret = drm_modeset_backoff(ctx);
48 * if (!ret)
49 * goto retry;
50 * }
51 * if (ret)
52 * goto out;
53 * }
54 * ... do stuff ...
55 * out:
56 * drm_modeset_drop_locks(ctx);
57 * drm_modeset_acquire_fini(ctx);
58 *
59 * If all that is needed is a single modeset lock, then the &struct
60 * drm_modeset_acquire_ctx is not needed and the locking can be simplified
61 * by passing a NULL instead of ctx in the drm_modeset_lock() call or
62 * calling drm_modeset_lock_single_interruptible(). To unlock afterwards
63 * call drm_modeset_unlock().
64 *
65 * On top of these per-object locks using &ww_mutex there's also an overall
66 * &drm_mode_config.mutex, for protecting everything else. Mostly this means
67 * probe state of connectors, and preventing hotplug add/removal of connectors.
68 *
69 * Finally there's a bunch of dedicated locks to protect drm core internal
70 * lists and lookup data structures.
71 */
72
73static DEFINE_WW_CLASS(crtc_ww_class);
74
75/**
76 * drm_modeset_lock_all - take all modeset locks
77 * @dev: DRM device
78 *
79 * This function takes all modeset locks, suitable where a more fine-grained
80 * scheme isn't (yet) implemented. Locks must be dropped by calling the
81 * drm_modeset_unlock_all() function.
82 *
83 * This function is deprecated. It allocates a lock acquisition context and
84 * stores it in &drm_device.mode_config. This facilitate conversion of
85 * existing code because it removes the need to manually deal with the
86 * acquisition context, but it is also brittle because the context is global
87 * and care must be taken not to nest calls. New code should use the
88 * drm_modeset_lock_all_ctx() function and pass in the context explicitly.
89 */
90void drm_modeset_lock_all(struct drm_device *dev)
91{
92 struct drm_mode_config *config = &dev->mode_config;
93 struct drm_modeset_acquire_ctx *ctx;
94 int ret;
95
96 ctx = kzalloc(sizeof(*ctx), GFP_KERNEL | __GFP_NOFAIL);
97 if (WARN_ON(!ctx))
98 return;
99
100 mutex_lock(&config->mutex);
101
102 drm_modeset_acquire_init(ctx, 0);
103
104retry:
105 ret = drm_modeset_lock_all_ctx(dev, ctx);
106 if (ret < 0) {
107 if (ret == -EDEADLK) {
108 drm_modeset_backoff(ctx);
109 goto retry;
110 }
111
112 drm_modeset_acquire_fini(ctx);
113 kfree(ctx);
114 return;
115 }
116 ww_acquire_done(&ctx->ww_ctx);
117
118 WARN_ON(config->acquire_ctx);
119
120 /*
121 * We hold the locks now, so it is safe to stash the acquisition
122 * context for drm_modeset_unlock_all().
123 */
124 config->acquire_ctx = ctx;
125
126 drm_warn_on_modeset_not_all_locked(dev);
127}
128EXPORT_SYMBOL(drm_modeset_lock_all);
129
130/**
131 * drm_modeset_unlock_all - drop all modeset locks
132 * @dev: DRM device
133 *
134 * This function drops all modeset locks taken by a previous call to the
135 * drm_modeset_lock_all() function.
136 *
137 * This function is deprecated. It uses the lock acquisition context stored
138 * in &drm_device.mode_config. This facilitates conversion of existing
139 * code because it removes the need to manually deal with the acquisition
140 * context, but it is also brittle because the context is global and care must
141 * be taken not to nest calls. New code should pass the acquisition context
142 * directly to the drm_modeset_drop_locks() function.
143 */
144void drm_modeset_unlock_all(struct drm_device *dev)
145{
146 struct drm_mode_config *config = &dev->mode_config;
147 struct drm_modeset_acquire_ctx *ctx = config->acquire_ctx;
148
149 if (WARN_ON(!ctx))
150 return;
151
152 config->acquire_ctx = NULL;
153 drm_modeset_drop_locks(ctx);
154 drm_modeset_acquire_fini(ctx);
155
156 kfree(ctx);
157
158 mutex_unlock(&dev->mode_config.mutex);
159}
160EXPORT_SYMBOL(drm_modeset_unlock_all);
161
162/**
163 * drm_warn_on_modeset_not_all_locked - check that all modeset locks are locked
164 * @dev: device
165 *
166 * Useful as a debug assert.
167 */
168void drm_warn_on_modeset_not_all_locked(struct drm_device *dev)
169{
170 struct drm_crtc *crtc;
171
172 /* Locking is currently fubar in the panic handler. */
173 if (oops_in_progress)
174 return;
175
176 drm_for_each_crtc(crtc, dev)
177 WARN_ON(!drm_modeset_is_locked(&crtc->mutex));
178
179 WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
180 WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
181}
182EXPORT_SYMBOL(drm_warn_on_modeset_not_all_locked);
183
184/**
185 * drm_modeset_acquire_init - initialize acquire context
186 * @ctx: the acquire context
187 * @flags: 0 or %DRM_MODESET_ACQUIRE_INTERRUPTIBLE
188 *
189 * When passing %DRM_MODESET_ACQUIRE_INTERRUPTIBLE to @flags,
190 * all calls to drm_modeset_lock() will perform an interruptible
191 * wait.
192 */
193void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx,
194 uint32_t flags)
195{
196 memset(ctx, 0, sizeof(*ctx));
197 ww_acquire_init(&ctx->ww_ctx, &crtc_ww_class);
198 INIT_LIST_HEAD(&ctx->locked);
199
200 if (flags & DRM_MODESET_ACQUIRE_INTERRUPTIBLE)
201 ctx->interruptible = true;
202}
203EXPORT_SYMBOL(drm_modeset_acquire_init);
204
205/**
206 * drm_modeset_acquire_fini - cleanup acquire context
207 * @ctx: the acquire context
208 */
209void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx)
210{
211 ww_acquire_fini(&ctx->ww_ctx);
212}
213EXPORT_SYMBOL(drm_modeset_acquire_fini);
214
215/**
216 * drm_modeset_drop_locks - drop all locks
217 * @ctx: the acquire context
218 *
219 * Drop all locks currently held against this acquire context.
220 */
221void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx *ctx)
222{
223 WARN_ON(ctx->contended);
224 while (!list_empty(&ctx->locked)) {
225 struct drm_modeset_lock *lock;
226
227 lock = list_first_entry(&ctx->locked,
228 struct drm_modeset_lock, head);
229
230 drm_modeset_unlock(lock);
231 }
232}
233EXPORT_SYMBOL(drm_modeset_drop_locks);
234
235static inline int modeset_lock(struct drm_modeset_lock *lock,
236 struct drm_modeset_acquire_ctx *ctx,
237 bool interruptible, bool slow)
238{
239 int ret;
240
241 WARN_ON(ctx->contended);
242
243 if (ctx->trylock_only) {
244 lockdep_assert_held(&ctx->ww_ctx);
245
246 if (!ww_mutex_trylock(&lock->mutex))
247 return -EBUSY;
248 else
249 return 0;
250 } else if (interruptible && slow) {
251 ret = ww_mutex_lock_slow_interruptible(&lock->mutex, &ctx->ww_ctx);
252 } else if (interruptible) {
253 ret = ww_mutex_lock_interruptible(&lock->mutex, &ctx->ww_ctx);
254 } else if (slow) {
255 ww_mutex_lock_slow(&lock->mutex, &ctx->ww_ctx);
256 ret = 0;
257 } else {
258 ret = ww_mutex_lock(&lock->mutex, &ctx->ww_ctx);
259 }
260 if (!ret) {
261 WARN_ON(!list_empty(&lock->head));
262 list_add(&lock->head, &ctx->locked);
263 } else if (ret == -EALREADY) {
264 /* we already hold the lock.. this is fine. For atomic
265 * we will need to be able to drm_modeset_lock() things
266 * without having to keep track of what is already locked
267 * or not.
268 */
269 ret = 0;
270 } else if (ret == -EDEADLK) {
271 ctx->contended = lock;
272 }
273
274 return ret;
275}
276
277/**
278 * drm_modeset_backoff - deadlock avoidance backoff
279 * @ctx: the acquire context
280 *
281 * If deadlock is detected (ie. drm_modeset_lock() returns -EDEADLK),
282 * you must call this function to drop all currently held locks and
283 * block until the contended lock becomes available.
284 *
285 * This function returns 0 on success, or -ERESTARTSYS if this context
286 * is initialized with %DRM_MODESET_ACQUIRE_INTERRUPTIBLE and the
287 * wait has been interrupted.
288 */
289int drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx)
290{
291 struct drm_modeset_lock *contended = ctx->contended;
292
293 ctx->contended = NULL;
294
295 if (WARN_ON(!contended))
296 return 0;
297
298 drm_modeset_drop_locks(ctx);
299
300 return modeset_lock(contended, ctx, ctx->interruptible, true);
301}
302EXPORT_SYMBOL(drm_modeset_backoff);
303
304/**
305 * drm_modeset_lock_init - initialize lock
306 * @lock: lock to init
307 */
308void drm_modeset_lock_init(struct drm_modeset_lock *lock)
309{
310 ww_mutex_init(&lock->mutex, &crtc_ww_class);
311 INIT_LIST_HEAD(&lock->head);
312}
313EXPORT_SYMBOL(drm_modeset_lock_init);
314
315/**
316 * drm_modeset_lock - take modeset lock
317 * @lock: lock to take
318 * @ctx: acquire ctx
319 *
320 * If @ctx is not NULL, then its ww acquire context is used and the
321 * lock will be tracked by the context and can be released by calling
322 * drm_modeset_drop_locks(). If -EDEADLK is returned, this means a
323 * deadlock scenario has been detected and it is an error to attempt
324 * to take any more locks without first calling drm_modeset_backoff().
325 *
326 * If the @ctx is not NULL and initialized with
327 * %DRM_MODESET_ACQUIRE_INTERRUPTIBLE, this function will fail with
328 * -ERESTARTSYS when interrupted.
329 *
330 * If @ctx is NULL then the function call behaves like a normal,
331 * uninterruptible non-nesting mutex_lock() call.
332 */
333int drm_modeset_lock(struct drm_modeset_lock *lock,
334 struct drm_modeset_acquire_ctx *ctx)
335{
336 if (ctx)
337 return modeset_lock(lock, ctx, ctx->interruptible, false);
338
339 ww_mutex_lock(&lock->mutex, NULL);
340 return 0;
341}
342EXPORT_SYMBOL(drm_modeset_lock);
343
344/**
345 * drm_modeset_lock_single_interruptible - take a single modeset lock
346 * @lock: lock to take
347 *
348 * This function behaves as drm_modeset_lock() with a NULL context,
349 * but performs interruptible waits.
350 *
351 * This function returns 0 on success, or -ERESTARTSYS when interrupted.
352 */
353int drm_modeset_lock_single_interruptible(struct drm_modeset_lock *lock)
354{
355 return ww_mutex_lock_interruptible(&lock->mutex, NULL);
356}
357EXPORT_SYMBOL(drm_modeset_lock_single_interruptible);
358
359/**
360 * drm_modeset_unlock - drop modeset lock
361 * @lock: lock to release
362 */
363void drm_modeset_unlock(struct drm_modeset_lock *lock)
364{
365 list_del_init(&lock->head);
366 ww_mutex_unlock(&lock->mutex);
367}
368EXPORT_SYMBOL(drm_modeset_unlock);
369
370/**
371 * drm_modeset_lock_all_ctx - take all modeset locks
372 * @dev: DRM device
373 * @ctx: lock acquisition context
374 *
375 * This function takes all modeset locks, suitable where a more fine-grained
376 * scheme isn't (yet) implemented.
377 *
378 * Unlike drm_modeset_lock_all(), it doesn't take the &drm_mode_config.mutex
379 * since that lock isn't required for modeset state changes. Callers which
380 * need to grab that lock too need to do so outside of the acquire context
381 * @ctx.
382 *
383 * Locks acquired with this function should be released by calling the
384 * drm_modeset_drop_locks() function on @ctx.
385 *
386 * Returns: 0 on success or a negative error-code on failure.
387 */
388int drm_modeset_lock_all_ctx(struct drm_device *dev,
389 struct drm_modeset_acquire_ctx *ctx)
390{
391 struct drm_crtc *crtc;
392 struct drm_plane *plane;
393 int ret;
394
395 ret = drm_modeset_lock(&dev->mode_config.connection_mutex, ctx);
396 if (ret)
397 return ret;
398
399 drm_for_each_crtc(crtc, dev) {
400 ret = drm_modeset_lock(&crtc->mutex, ctx);
401 if (ret)
402 return ret;
403 }
404
405 drm_for_each_plane(plane, dev) {
406 ret = drm_modeset_lock(&plane->mutex, ctx);
407 if (ret)
408 return ret;
409 }
410
411 return 0;
412}
413EXPORT_SYMBOL(drm_modeset_lock_all_ctx);