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7  * to deal in the Software without restriction, including without limitation
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10  * Software is furnished to do so, subject to the following conditions:
13  * all copies or substantial portions of the Software.
15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
20  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
21  * OTHER DEALINGS IN THE SOFTWARE.
35  * to use &ww_mutex and acquire-contexts to avoid deadlocks.  But because
37  * of extra utility/tracking out of our acquire-ctx.  This is provided
40  * For basic principles of &ww_mutex, see: Documentation/locking/ww-mutex-design.rst
48  *         if (ret == -EDEADLK) {
71  * On top of these per-object locks using &ww_mutex there's also an overall
129  * drm_modeset_lock_all - take all modeset locks
132  * This function takes all modeset locks, suitable where a more fine-grained
145 	struct drm_mode_config *config = &dev->mode_config;  in drm_modeset_lock_all()
153 	mutex_lock(&config->mutex);  in drm_modeset_lock_all()
160 		if (ret == -EDEADLK) {  in drm_modeset_lock_all()
169 	ww_acquire_done(&ctx->ww_ctx);  in drm_modeset_lock_all()
171 	WARN_ON(config->acquire_ctx);  in drm_modeset_lock_all()
177 	config->acquire_ctx = ctx;  in drm_modeset_lock_all()
184  * drm_modeset_unlock_all - drop all modeset locks
199 	struct drm_mode_config *config = &dev->mode_config;  in drm_modeset_unlock_all()
200 	struct drm_modeset_acquire_ctx *ctx = config->acquire_ctx;  in drm_modeset_unlock_all()
205 	config->acquire_ctx = NULL;  in drm_modeset_unlock_all()
211 	mutex_unlock(&dev->mode_config.mutex);  in drm_modeset_unlock_all()
216  * drm_warn_on_modeset_not_all_locked - check that all modeset locks are locked
230 		WARN_ON(!drm_modeset_is_locked(&crtc->mutex));  in drm_warn_on_modeset_not_all_locked()
232 	WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));  in drm_warn_on_modeset_not_all_locked()
233 	WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));  in drm_warn_on_modeset_not_all_locked()
238  * drm_modeset_acquire_init - initialize acquire context
250 	ww_acquire_init(&ctx->ww_ctx, &crtc_ww_class);  in drm_modeset_acquire_init()
251 	INIT_LIST_HEAD(&ctx->locked);  in drm_modeset_acquire_init()
254 		ctx->interruptible = true;  in drm_modeset_acquire_init()
259  * drm_modeset_acquire_fini - cleanup acquire context
264 	ww_acquire_fini(&ctx->ww_ctx);  in drm_modeset_acquire_fini()
269  * drm_modeset_drop_locks - drop all locks
276 	if (WARN_ON(ctx->contended))  in drm_modeset_drop_locks()
277 		__drm_stack_depot_print(ctx->stack_depot);  in drm_modeset_drop_locks()
279 	while (!list_empty(&ctx->locked)) {  in drm_modeset_drop_locks()
282 		lock = list_first_entry(&ctx->locked,  in drm_modeset_drop_locks()
296 	if (WARN_ON(ctx->contended))  in modeset_lock()
297 		__drm_stack_depot_print(ctx->stack_depot);  in modeset_lock()
299 	if (ctx->trylock_only) {  in modeset_lock()
300 		lockdep_assert_held(&ctx->ww_ctx);  in modeset_lock()
302 		if (!ww_mutex_trylock(&lock->mutex, NULL))  in modeset_lock()
303 			return -EBUSY;  in modeset_lock()
307 		ret = ww_mutex_lock_slow_interruptible(&lock->mutex, &ctx->ww_ctx);  in modeset_lock()
309 		ret = ww_mutex_lock_interruptible(&lock->mutex, &ctx->ww_ctx);  in modeset_lock()
311 		ww_mutex_lock_slow(&lock->mutex, &ctx->ww_ctx);  in modeset_lock()
314 		ret = ww_mutex_lock(&lock->mutex, &ctx->ww_ctx);  in modeset_lock()
317 		WARN_ON(!list_empty(&lock->head));  in modeset_lock()
318 		list_add(&lock->head, &ctx->locked);  in modeset_lock()
319 	} else if (ret == -EALREADY) {  in modeset_lock()
322 		 * without having to keep track of what is already locked  in modeset_lock()
326 	} else if (ret == -EDEADLK) {  in modeset_lock()
327 		ctx->contended = lock;  in modeset_lock()
328 		ctx->stack_depot = __drm_stack_depot_save();  in modeset_lock()
335  * drm_modeset_backoff - deadlock avoidance backoff
338  * If deadlock is detected (ie. drm_modeset_lock() returns -EDEADLK),
342  * This function returns 0 on success, or -ERESTARTSYS if this context
348 	struct drm_modeset_lock *contended = ctx->contended;  in drm_modeset_backoff()
350 	ctx->contended = NULL;  in drm_modeset_backoff()
351 	ctx->stack_depot = 0;  in drm_modeset_backoff()
358 	return modeset_lock(contended, ctx, ctx->interruptible, true);  in drm_modeset_backoff()
363  * drm_modeset_lock_init - initialize lock
368 	ww_mutex_init(&lock->mutex, &crtc_ww_class);  in drm_modeset_lock_init()
369 	INIT_LIST_HEAD(&lock->head);  in drm_modeset_lock_init()
375  * drm_modeset_lock - take modeset lock
381  * drm_modeset_drop_locks().  If -EDEADLK is returned, this means a
387  * -ERESTARTSYS when interrupted.
390  * uninterruptible non-nesting mutex_lock() call.
396 		return modeset_lock(lock, ctx, ctx->interruptible, false);  in drm_modeset_lock()
398 	ww_mutex_lock(&lock->mutex, NULL);  in drm_modeset_lock()
404  * drm_modeset_lock_single_interruptible - take a single modeset lock
410  * This function returns 0 on success, or -ERESTARTSYS when interrupted.
414 	return ww_mutex_lock_interruptible(&lock->mutex, NULL);  in drm_modeset_lock_single_interruptible()
419  * drm_modeset_unlock - drop modeset lock
424 	list_del_init(&lock->head);  in drm_modeset_unlock()
425 	ww_mutex_unlock(&lock->mutex);  in drm_modeset_unlock()
430  * drm_modeset_lock_all_ctx - take all modeset locks
434  * This function takes all modeset locks, suitable where a more fine-grained
447  * Returns: 0 on success or a negative error-code on failure.
457 	ret = drm_modeset_lock(&dev->mode_config.connection_mutex, ctx);  in drm_modeset_lock_all_ctx()
462 		ret = drm_modeset_lock(&crtc->mutex, ctx);  in drm_modeset_lock_all_ctx()
468 		ret = drm_modeset_lock(&plane->mutex, ctx);  in drm_modeset_lock_all_ctx()
474 		ret = drm_modeset_lock(&privobj->lock, ctx);  in drm_modeset_lock_all_ctx()