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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/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/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_debug_printer("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);