2 * Copyright (C) 2014 Red Hat
3 * Author: Rob Clark <robdclark@gmail.com>
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:
12 * The above copyright notice and this permission notice shall be included in
13 * all copies or substantial portions of the Software.
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.
25 #include <drm/drm_crtc.h>
26 #include <drm/drm_modeset_lock.h>
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.
38 * For basic principles of ww_mutex, see: Documentation/ww-mutex-design.txt
40 * The basic usage pattern is to:
42 * drm_modeset_acquire_init(&ctx)
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);
54 * drm_modeset_drop_locks(&ctx);
55 * drm_modeset_acquire_fini(&ctx);
60 * drm_modeset_lock_all - take all modeset locks
63 * This function takes all modeset locks, suitable where a more fine-grained
64 * scheme isn't (yet) implemented. Locks must be dropped with
65 * drm_modeset_unlock_all.
67 void drm_modeset_lock_all(struct drm_device
*dev
)
69 struct drm_mode_config
*config
= &dev
->mode_config
;
70 struct drm_modeset_acquire_ctx
*ctx
;
73 ctx
= kzalloc(sizeof(*ctx
), GFP_KERNEL
);
77 mutex_lock(&config
->mutex
);
79 drm_modeset_acquire_init(ctx
, 0);
82 ret
= drm_modeset_lock(&config
->connection_mutex
, ctx
);
85 ret
= drm_modeset_lock_all_crtcs(dev
, ctx
);
89 WARN_ON(config
->acquire_ctx
);
91 /* now we hold the locks, so now that it is safe, stash the
92 * ctx for drm_modeset_unlock_all():
94 config
->acquire_ctx
= ctx
;
96 drm_warn_on_modeset_not_all_locked(dev
);
101 if (ret
== -EDEADLK
) {
102 drm_modeset_backoff(ctx
);
106 EXPORT_SYMBOL(drm_modeset_lock_all
);
109 * drm_modeset_unlock_all - drop all modeset locks
112 * This function drop all modeset locks taken by drm_modeset_lock_all.
114 void drm_modeset_unlock_all(struct drm_device
*dev
)
116 struct drm_mode_config
*config
= &dev
->mode_config
;
117 struct drm_modeset_acquire_ctx
*ctx
= config
->acquire_ctx
;
122 config
->acquire_ctx
= NULL
;
123 drm_modeset_drop_locks(ctx
);
124 drm_modeset_acquire_fini(ctx
);
128 mutex_unlock(&dev
->mode_config
.mutex
);
130 EXPORT_SYMBOL(drm_modeset_unlock_all
);
133 * drm_modeset_lock_crtc - lock crtc with hidden acquire ctx
136 * This function locks the given crtc using a hidden acquire context. This is
137 * necessary so that drivers internally using the atomic interfaces can grab
138 * further locks with the lock acquire context.
140 void drm_modeset_lock_crtc(struct drm_crtc
*crtc
)
142 struct drm_modeset_acquire_ctx
*ctx
;
145 ctx
= kzalloc(sizeof(*ctx
), GFP_KERNEL
);
149 drm_modeset_acquire_init(ctx
, 0);
152 ret
= drm_modeset_lock(&crtc
->mutex
, ctx
);
156 WARN_ON(crtc
->acquire_ctx
);
158 /* now we hold the locks, so now that it is safe, stash the
159 * ctx for drm_modeset_unlock_crtc():
161 crtc
->acquire_ctx
= ctx
;
166 if (ret
== -EDEADLK
) {
167 drm_modeset_backoff(ctx
);
171 EXPORT_SYMBOL(drm_modeset_lock_crtc
);
174 * drm_modeset_legacy_acquire_ctx - find acquire ctx for legacy ioctls
177 * Legacy ioctl operations like cursor updates or page flips only have per-crtc
178 * locking, and store the acquire ctx in the corresponding crtc. All other
179 * legacy operations take all locks and use a global acquire context. This
180 * function grabs the right one.
182 struct drm_modeset_acquire_ctx
*
183 drm_modeset_legacy_acquire_ctx(struct drm_crtc
*crtc
)
185 if (crtc
->acquire_ctx
)
186 return crtc
->acquire_ctx
;
188 WARN_ON(!crtc
->dev
->mode_config
.acquire_ctx
);
190 return crtc
->dev
->mode_config
.acquire_ctx
;
192 EXPORT_SYMBOL(drm_modeset_legacy_acquire_ctx
);
195 * drm_modeset_unlock_crtc - drop crtc lock
198 * This drops the crtc lock acquire with drm_modeset_lock_crtc() and all other
199 * locks acquired through the hidden context.
201 void drm_modeset_unlock_crtc(struct drm_crtc
*crtc
)
203 struct drm_modeset_acquire_ctx
*ctx
= crtc
->acquire_ctx
;
208 crtc
->acquire_ctx
= NULL
;
209 drm_modeset_drop_locks(ctx
);
210 drm_modeset_acquire_fini(ctx
);
214 EXPORT_SYMBOL(drm_modeset_unlock_crtc
);
217 * drm_warn_on_modeset_not_all_locked - check that all modeset locks are locked
220 * Useful as a debug assert.
222 void drm_warn_on_modeset_not_all_locked(struct drm_device
*dev
)
224 struct drm_crtc
*crtc
;
226 /* Locking is currently fubar in the panic handler. */
227 if (oops_in_progress
)
230 list_for_each_entry(crtc
, &dev
->mode_config
.crtc_list
, head
)
231 WARN_ON(!drm_modeset_is_locked(&crtc
->mutex
));
233 WARN_ON(!drm_modeset_is_locked(&dev
->mode_config
.connection_mutex
));
234 WARN_ON(!mutex_is_locked(&dev
->mode_config
.mutex
));
236 EXPORT_SYMBOL(drm_warn_on_modeset_not_all_locked
);
239 * drm_modeset_acquire_init - initialize acquire context
240 * @ctx: the acquire context
243 void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx
*ctx
,
246 memset(ctx
, 0, sizeof(*ctx
));
247 ww_acquire_init(&ctx
->ww_ctx
, &crtc_ww_class
);
248 INIT_LIST_HEAD(&ctx
->locked
);
250 EXPORT_SYMBOL(drm_modeset_acquire_init
);
253 * drm_modeset_acquire_fini - cleanup acquire context
254 * @ctx: the acquire context
256 void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx
*ctx
)
258 ww_acquire_fini(&ctx
->ww_ctx
);
260 EXPORT_SYMBOL(drm_modeset_acquire_fini
);
263 * drm_modeset_drop_locks - drop all locks
264 * @ctx: the acquire context
266 * Drop all locks currently held against this acquire context.
268 void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx
*ctx
)
270 WARN_ON(ctx
->contended
);
271 while (!list_empty(&ctx
->locked
)) {
272 struct drm_modeset_lock
*lock
;
274 lock
= list_first_entry(&ctx
->locked
,
275 struct drm_modeset_lock
, head
);
277 drm_modeset_unlock(lock
);
280 EXPORT_SYMBOL(drm_modeset_drop_locks
);
282 static inline int modeset_lock(struct drm_modeset_lock
*lock
,
283 struct drm_modeset_acquire_ctx
*ctx
,
284 bool interruptible
, bool slow
)
288 WARN_ON(ctx
->contended
);
290 if (interruptible
&& slow
) {
291 ret
= ww_mutex_lock_slow_interruptible(&lock
->mutex
, &ctx
->ww_ctx
);
292 } else if (interruptible
) {
293 ret
= ww_mutex_lock_interruptible(&lock
->mutex
, &ctx
->ww_ctx
);
295 ww_mutex_lock_slow(&lock
->mutex
, &ctx
->ww_ctx
);
298 ret
= ww_mutex_lock(&lock
->mutex
, &ctx
->ww_ctx
);
301 WARN_ON(!list_empty(&lock
->head
));
302 list_add(&lock
->head
, &ctx
->locked
);
303 } else if (ret
== -EALREADY
) {
304 /* we already hold the lock.. this is fine. For atomic
305 * we will need to be able to drm_modeset_lock() things
306 * without having to keep track of what is already locked
310 } else if (ret
== -EDEADLK
) {
311 ctx
->contended
= lock
;
317 static int modeset_backoff(struct drm_modeset_acquire_ctx
*ctx
,
320 struct drm_modeset_lock
*contended
= ctx
->contended
;
322 ctx
->contended
= NULL
;
324 if (WARN_ON(!contended
))
327 drm_modeset_drop_locks(ctx
);
329 return modeset_lock(contended
, ctx
, interruptible
, true);
333 * drm_modeset_backoff - deadlock avoidance backoff
334 * @ctx: the acquire context
336 * If deadlock is detected (ie. drm_modeset_lock() returns -EDEADLK),
337 * you must call this function to drop all currently held locks and
338 * block until the contended lock becomes available.
340 void drm_modeset_backoff(struct drm_modeset_acquire_ctx
*ctx
)
342 modeset_backoff(ctx
, false);
344 EXPORT_SYMBOL(drm_modeset_backoff
);
347 * drm_modeset_backoff_interruptible - deadlock avoidance backoff
348 * @ctx: the acquire context
350 * Interruptible version of drm_modeset_backoff()
352 int drm_modeset_backoff_interruptible(struct drm_modeset_acquire_ctx
*ctx
)
354 return modeset_backoff(ctx
, true);
356 EXPORT_SYMBOL(drm_modeset_backoff_interruptible
);
359 * drm_modeset_lock - take modeset lock
360 * @lock: lock to take
363 * If ctx is not NULL, then its ww acquire context is used and the
364 * lock will be tracked by the context and can be released by calling
365 * drm_modeset_drop_locks(). If -EDEADLK is returned, this means a
366 * deadlock scenario has been detected and it is an error to attempt
367 * to take any more locks without first calling drm_modeset_backoff().
369 int drm_modeset_lock(struct drm_modeset_lock
*lock
,
370 struct drm_modeset_acquire_ctx
*ctx
)
373 return modeset_lock(lock
, ctx
, false, false);
375 ww_mutex_lock(&lock
->mutex
, NULL
);
378 EXPORT_SYMBOL(drm_modeset_lock
);
381 * drm_modeset_lock_interruptible - take modeset lock
382 * @lock: lock to take
385 * Interruptible version of drm_modeset_lock()
387 int drm_modeset_lock_interruptible(struct drm_modeset_lock
*lock
,
388 struct drm_modeset_acquire_ctx
*ctx
)
391 return modeset_lock(lock
, ctx
, true, false);
393 return ww_mutex_lock_interruptible(&lock
->mutex
, NULL
);
395 EXPORT_SYMBOL(drm_modeset_lock_interruptible
);
398 * drm_modeset_unlock - drop modeset lock
399 * @lock: lock to release
401 void drm_modeset_unlock(struct drm_modeset_lock
*lock
)
403 list_del_init(&lock
->head
);
404 ww_mutex_unlock(&lock
->mutex
);
406 EXPORT_SYMBOL(drm_modeset_unlock
);
408 /* Temporary.. until we have sufficiently fine grained locking, there
409 * are a couple scenarios where it is convenient to grab all crtc locks.
410 * It is planned to remove this:
412 int drm_modeset_lock_all_crtcs(struct drm_device
*dev
,
413 struct drm_modeset_acquire_ctx
*ctx
)
415 struct drm_mode_config
*config
= &dev
->mode_config
;
416 struct drm_crtc
*crtc
;
419 list_for_each_entry(crtc
, &config
->crtc_list
, head
) {
420 ret
= drm_modeset_lock(&crtc
->mutex
, ctx
);
427 EXPORT_SYMBOL(drm_modeset_lock_all_crtcs
);