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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#include <drm/drm_print.h>
29
30/**
31 * DOC: kms locking
32 *
33 * As KMS moves toward more fine grained locking, and atomic ioctl where
34 * userspace can indirectly control locking order, it becomes necessary
35 * to use &ww_mutex and acquire-contexts to avoid deadlocks. But because
36 * the locking is more distributed around the driver code, we want a bit
37 * of extra utility/tracking out of our acquire-ctx. This is provided
38 * by &struct drm_modeset_lock and &struct drm_modeset_acquire_ctx.
39 *
40 * For basic principles of &ww_mutex, see: Documentation/locking/ww-mutex-design.rst
41 *
42 * The basic usage pattern is to::
43 *
44 * drm_modeset_acquire_init(ctx, DRM_MODESET_ACQUIRE_INTERRUPTIBLE)
45 * retry:
46 * foreach (lock in random_ordered_set_of_locks) {
47 * ret = drm_modeset_lock(lock, ctx)
48 * if (ret == -EDEADLK) {
49 * ret = drm_modeset_backoff(ctx);
50 * if (!ret)
51 * goto retry;
52 * }
53 * if (ret)
54 * goto out;
55 * }
56 * ... do stuff ...
57 * out:
58 * drm_modeset_drop_locks(ctx);
59 * drm_modeset_acquire_fini(ctx);
60 *
61 * For convenience this control flow is implemented in
62 * DRM_MODESET_LOCK_ALL_BEGIN() and DRM_MODESET_LOCK_ALL_END() for the case
63 * where all modeset locks need to be taken through drm_modeset_lock_all_ctx().
64 *
65 * If all that is needed is a single modeset lock, then the &struct
66 * drm_modeset_acquire_ctx is not needed and the locking can be simplified
67 * by passing a NULL instead of ctx in the drm_modeset_lock() call or
68 * calling drm_modeset_lock_single_interruptible(). To unlock afterwards
69 * call drm_modeset_unlock().
70 *
71 * On top of these per-object locks using &ww_mutex there's also an overall
72 * &drm_mode_config.mutex, for protecting everything else. Mostly this means
73 * probe state of connectors, and preventing hotplug add/removal of connectors.
74 *
75 * Finally there's a bunch of dedicated locks to protect drm core internal
76 * lists and lookup data structures.
77 */
78
79static DEFINE_WW_CLASS(crtc_ww_class);
80
81#if IS_ENABLED(CONFIG_DRM_DEBUG_MODESET_LOCK)
82static noinline depot_stack_handle_t __drm_stack_depot_save(void)
83{
84 unsigned long entries[8];
85 unsigned int n;
86
87 n = stack_trace_save(entries, ARRAY_SIZE(entries), 1);
88
89 return stack_depot_save(entries, n, GFP_NOWAIT | __GFP_NOWARN);
90}
91
92static void __drm_stack_depot_print(depot_stack_handle_t stack_depot)
93{
94 struct drm_printer p = drm_dbg_printer(NULL, DRM_UT_KMS, "drm_modeset_lock");
95 unsigned long *entries;
96 unsigned int nr_entries;
97 char *buf;
98
99 buf = kmalloc(PAGE_SIZE, GFP_NOWAIT | __GFP_NOWARN);
100 if (!buf)
101 return;
102
103 nr_entries = stack_depot_fetch(stack_depot, &entries);
104 stack_trace_snprint(buf, PAGE_SIZE, entries, nr_entries, 2);
105
106 drm_printf(&p, "attempting to lock a contended lock without backoff:\n%s", buf);
107
108 kfree(buf);
109}
110
111static void __drm_stack_depot_init(void)
112{
113 stack_depot_init();
114}
115#else /* CONFIG_DRM_DEBUG_MODESET_LOCK */
116static depot_stack_handle_t __drm_stack_depot_save(void)
117{
118 return 0;
119}
120static void __drm_stack_depot_print(depot_stack_handle_t stack_depot)
121{
122}
123static void __drm_stack_depot_init(void)
124{
125}
126#endif /* CONFIG_DRM_DEBUG_MODESET_LOCK */
127
128/**
129 * drm_modeset_lock_all - take all modeset locks
130 * @dev: DRM device
131 *
132 * This function takes all modeset locks, suitable where a more fine-grained
133 * scheme isn't (yet) implemented. Locks must be dropped by calling the
134 * drm_modeset_unlock_all() function.
135 *
136 * This function is deprecated. It allocates a lock acquisition context and
137 * stores it in &drm_device.mode_config. This facilitate conversion of
138 * existing code because it removes the need to manually deal with the
139 * acquisition context, but it is also brittle because the context is global
140 * and care must be taken not to nest calls. New code should use the
141 * drm_modeset_lock_all_ctx() function and pass in the context explicitly.
142 */
143void drm_modeset_lock_all(struct drm_device *dev)
144{
145 struct drm_mode_config *config = &dev->mode_config;
146 struct drm_modeset_acquire_ctx *ctx;
147 int ret;
148
149 ctx = kzalloc(sizeof(*ctx), GFP_KERNEL | __GFP_NOFAIL);
150 if (WARN_ON(!ctx))
151 return;
152
153 mutex_lock(&config->mutex);
154
155 drm_modeset_acquire_init(ctx, 0);
156
157retry:
158 ret = drm_modeset_lock_all_ctx(dev, ctx);
159 if (ret < 0) {
160 if (ret == -EDEADLK) {
161 drm_modeset_backoff(ctx);
162 goto retry;
163 }
164
165 drm_modeset_acquire_fini(ctx);
166 kfree(ctx);
167 return;
168 }
169 ww_acquire_done(&ctx->ww_ctx);
170
171 WARN_ON(config->acquire_ctx);
172
173 /*
174 * We hold the locks now, so it is safe to stash the acquisition
175 * context for drm_modeset_unlock_all().
176 */
177 config->acquire_ctx = ctx;
178
179 drm_warn_on_modeset_not_all_locked(dev);
180}
181EXPORT_SYMBOL(drm_modeset_lock_all);
182
183/**
184 * drm_modeset_unlock_all - drop all modeset locks
185 * @dev: DRM device
186 *
187 * This function drops all modeset locks taken by a previous call to the
188 * drm_modeset_lock_all() function.
189 *
190 * This function is deprecated. It uses the lock acquisition context stored
191 * in &drm_device.mode_config. This facilitates conversion of existing
192 * code because it removes the need to manually deal with the acquisition
193 * context, but it is also brittle because the context is global and care must
194 * be taken not to nest calls. New code should pass the acquisition context
195 * directly to the drm_modeset_drop_locks() function.
196 */
197void drm_modeset_unlock_all(struct drm_device *dev)
198{
199 struct drm_mode_config *config = &dev->mode_config;
200 struct drm_modeset_acquire_ctx *ctx = config->acquire_ctx;
201
202 if (WARN_ON(!ctx))
203 return;
204
205 config->acquire_ctx = NULL;
206 drm_modeset_drop_locks(ctx);
207 drm_modeset_acquire_fini(ctx);
208
209 kfree(ctx);
210
211 mutex_unlock(&dev->mode_config.mutex);
212}
213EXPORT_SYMBOL(drm_modeset_unlock_all);
214
215/**
216 * drm_warn_on_modeset_not_all_locked - check that all modeset locks are locked
217 * @dev: device
218 *
219 * Useful as a debug assert.
220 */
221void drm_warn_on_modeset_not_all_locked(struct drm_device *dev)
222{
223 struct drm_crtc *crtc;
224
225 /* Locking is currently fubar in the panic handler. */
226 if (oops_in_progress)
227 return;
228
229 drm_for_each_crtc(crtc, dev)
230 WARN_ON(!drm_modeset_is_locked(&crtc->mutex));
231
232 WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
233 WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
234}
235EXPORT_SYMBOL(drm_warn_on_modeset_not_all_locked);
236
237/**
238 * drm_modeset_acquire_init - initialize acquire context
239 * @ctx: the acquire context
240 * @flags: 0 or %DRM_MODESET_ACQUIRE_INTERRUPTIBLE
241 *
242 * When passing %DRM_MODESET_ACQUIRE_INTERRUPTIBLE to @flags,
243 * all calls to drm_modeset_lock() will perform an interruptible
244 * wait.
245 */
246void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx,
247 uint32_t flags)
248{
249 memset(ctx, 0, sizeof(*ctx));
250 ww_acquire_init(&ctx->ww_ctx, &crtc_ww_class);
251 INIT_LIST_HEAD(&ctx->locked);
252
253 if (flags & DRM_MODESET_ACQUIRE_INTERRUPTIBLE)
254 ctx->interruptible = true;
255}
256EXPORT_SYMBOL(drm_modeset_acquire_init);
257
258/**
259 * drm_modeset_acquire_fini - cleanup acquire context
260 * @ctx: the acquire context
261 */
262void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx)
263{
264 ww_acquire_fini(&ctx->ww_ctx);
265}
266EXPORT_SYMBOL(drm_modeset_acquire_fini);
267
268/**
269 * drm_modeset_drop_locks - drop all locks
270 * @ctx: the acquire context
271 *
272 * Drop all locks currently held against this acquire context.
273 */
274void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx *ctx)
275{
276 if (WARN_ON(ctx->contended))
277 __drm_stack_depot_print(ctx->stack_depot);
278
279 while (!list_empty(&ctx->locked)) {
280 struct drm_modeset_lock *lock;
281
282 lock = list_first_entry(&ctx->locked,
283 struct drm_modeset_lock, head);
284
285 drm_modeset_unlock(lock);
286 }
287}
288EXPORT_SYMBOL(drm_modeset_drop_locks);
289
290static inline int modeset_lock(struct drm_modeset_lock *lock,
291 struct drm_modeset_acquire_ctx *ctx,
292 bool interruptible, bool slow)
293{
294 int ret;
295
296 if (WARN_ON(ctx->contended))
297 __drm_stack_depot_print(ctx->stack_depot);
298
299 if (ctx->trylock_only) {
300 lockdep_assert_held(&ctx->ww_ctx);
301
302 if (!ww_mutex_trylock(&lock->mutex, NULL))
303 return -EBUSY;
304 else
305 return 0;
306 } else if (interruptible && slow) {
307 ret = ww_mutex_lock_slow_interruptible(&lock->mutex, &ctx->ww_ctx);
308 } else if (interruptible) {
309 ret = ww_mutex_lock_interruptible(&lock->mutex, &ctx->ww_ctx);
310 } else if (slow) {
311 ww_mutex_lock_slow(&lock->mutex, &ctx->ww_ctx);
312 ret = 0;
313 } else {
314 ret = ww_mutex_lock(&lock->mutex, &ctx->ww_ctx);
315 }
316 if (!ret) {
317 WARN_ON(!list_empty(&lock->head));
318 list_add(&lock->head, &ctx->locked);
319 } else if (ret == -EALREADY) {
320 /* we already hold the lock.. this is fine. For atomic
321 * we will need to be able to drm_modeset_lock() things
322 * without having to keep track of what is already locked
323 * or not.
324 */
325 ret = 0;
326 } else if (ret == -EDEADLK) {
327 ctx->contended = lock;
328 ctx->stack_depot = __drm_stack_depot_save();
329 }
330
331 return ret;
332}
333
334/**
335 * drm_modeset_backoff - deadlock avoidance backoff
336 * @ctx: the acquire context
337 *
338 * If deadlock is detected (ie. drm_modeset_lock() returns -EDEADLK),
339 * you must call this function to drop all currently held locks and
340 * block until the contended lock becomes available.
341 *
342 * This function returns 0 on success, or -ERESTARTSYS if this context
343 * is initialized with %DRM_MODESET_ACQUIRE_INTERRUPTIBLE and the
344 * wait has been interrupted.
345 */
346int drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx)
347{
348 struct drm_modeset_lock *contended = ctx->contended;
349
350 ctx->contended = NULL;
351 ctx->stack_depot = 0;
352
353 if (WARN_ON(!contended))
354 return 0;
355
356 drm_modeset_drop_locks(ctx);
357
358 return modeset_lock(contended, ctx, ctx->interruptible, true);
359}
360EXPORT_SYMBOL(drm_modeset_backoff);
361
362/**
363 * drm_modeset_lock_init - initialize lock
364 * @lock: lock to init
365 */
366void drm_modeset_lock_init(struct drm_modeset_lock *lock)
367{
368 ww_mutex_init(&lock->mutex, &crtc_ww_class);
369 INIT_LIST_HEAD(&lock->head);
370 __drm_stack_depot_init();
371}
372EXPORT_SYMBOL(drm_modeset_lock_init);
373
374/**
375 * drm_modeset_lock - take modeset lock
376 * @lock: lock to take
377 * @ctx: acquire ctx
378 *
379 * If @ctx is not NULL, then its ww acquire context is used and the
380 * lock will be tracked by the context and can be released by calling
381 * drm_modeset_drop_locks(). If -EDEADLK is returned, this means a
382 * deadlock scenario has been detected and it is an error to attempt
383 * to take any more locks without first calling drm_modeset_backoff().
384 *
385 * If the @ctx is not NULL and initialized with
386 * %DRM_MODESET_ACQUIRE_INTERRUPTIBLE, this function will fail with
387 * -ERESTARTSYS when interrupted.
388 *
389 * If @ctx is NULL then the function call behaves like a normal,
390 * uninterruptible non-nesting mutex_lock() call.
391 */
392int drm_modeset_lock(struct drm_modeset_lock *lock,
393 struct drm_modeset_acquire_ctx *ctx)
394{
395 if (ctx)
396 return modeset_lock(lock, ctx, ctx->interruptible, false);
397
398 ww_mutex_lock(&lock->mutex, NULL);
399 return 0;
400}
401EXPORT_SYMBOL(drm_modeset_lock);
402
403/**
404 * drm_modeset_lock_single_interruptible - take a single modeset lock
405 * @lock: lock to take
406 *
407 * This function behaves as drm_modeset_lock() with a NULL context,
408 * but performs interruptible waits.
409 *
410 * This function returns 0 on success, or -ERESTARTSYS when interrupted.
411 */
412int drm_modeset_lock_single_interruptible(struct drm_modeset_lock *lock)
413{
414 return ww_mutex_lock_interruptible(&lock->mutex, NULL);
415}
416EXPORT_SYMBOL(drm_modeset_lock_single_interruptible);
417
418/**
419 * drm_modeset_unlock - drop modeset lock
420 * @lock: lock to release
421 */
422void drm_modeset_unlock(struct drm_modeset_lock *lock)
423{
424 list_del_init(&lock->head);
425 ww_mutex_unlock(&lock->mutex);
426}
427EXPORT_SYMBOL(drm_modeset_unlock);
428
429/**
430 * drm_modeset_lock_all_ctx - take all modeset locks
431 * @dev: DRM device
432 * @ctx: lock acquisition context
433 *
434 * This function takes all modeset locks, suitable where a more fine-grained
435 * scheme isn't (yet) implemented.
436 *
437 * Unlike drm_modeset_lock_all(), it doesn't take the &drm_mode_config.mutex
438 * since that lock isn't required for modeset state changes. Callers which
439 * need to grab that lock too need to do so outside of the acquire context
440 * @ctx.
441 *
442 * Locks acquired with this function should be released by calling the
443 * drm_modeset_drop_locks() function on @ctx.
444 *
445 * See also: DRM_MODESET_LOCK_ALL_BEGIN() and DRM_MODESET_LOCK_ALL_END()
446 *
447 * Returns: 0 on success or a negative error-code on failure.
448 */
449int drm_modeset_lock_all_ctx(struct drm_device *dev,
450 struct drm_modeset_acquire_ctx *ctx)
451{
452 struct drm_private_obj *privobj;
453 struct drm_crtc *crtc;
454 struct drm_plane *plane;
455 int ret;
456
457 ret = drm_modeset_lock(&dev->mode_config.connection_mutex, ctx);
458 if (ret)
459 return ret;
460
461 drm_for_each_crtc(crtc, dev) {
462 ret = drm_modeset_lock(&crtc->mutex, ctx);
463 if (ret)
464 return ret;
465 }
466
467 drm_for_each_plane(plane, dev) {
468 ret = drm_modeset_lock(&plane->mutex, ctx);
469 if (ret)
470 return ret;
471 }
472
473 drm_for_each_privobj(privobj, dev) {
474 ret = drm_modeset_lock(&privobj->lock, ctx);
475 if (ret)
476 return ret;
477 }
478
479 return 0;
480}
481EXPORT_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/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);