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Diffstat (limited to 'include/drm/drm_modeset_lock.h')
| -rw-r--r-- | include/drm/drm_modeset_lock.h | 215 |
1 files changed, 215 insertions, 0 deletions
diff --git a/include/drm/drm_modeset_lock.h b/include/drm/drm_modeset_lock.h new file mode 100644 index 000000000..ec4f543c3 --- /dev/null +++ b/include/drm/drm_modeset_lock.h @@ -0,0 +1,215 @@ +/* + * Copyright (C) 2014 Red Hat + * Author: Rob Clark <robdclark@gmail.com> + * + * Permission is hereby granted, free of charge, to any person obtaining a + * copy of this software and associated documentation files (the "Software"), + * to deal in the Software without restriction, including without limitation + * the rights to use, copy, modify, merge, publish, distribute, sublicense, + * and/or sell copies of the Software, and to permit persons to whom the + * Software is furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL + * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR + * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, + * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR + * OTHER DEALINGS IN THE SOFTWARE. + */ + +#ifndef DRM_MODESET_LOCK_H_ +#define DRM_MODESET_LOCK_H_ + +#include <linux/types.h> /* stackdepot.h is not self-contained */ +#include <linux/stackdepot.h> +#include <linux/ww_mutex.h> + +struct drm_modeset_lock; + +/** + * struct drm_modeset_acquire_ctx - locking context (see ww_acquire_ctx) + * @ww_ctx: base acquire ctx + * @contended: used internally for -EDEADLK handling + * @stack_depot: used internally for contention debugging + * @locked: list of held locks + * @trylock_only: trylock mode used in atomic contexts/panic notifiers + * @interruptible: whether interruptible locking should be used. + * + * Each thread competing for a set of locks must use one acquire + * ctx. And if any lock fxn returns -EDEADLK, it must backoff and + * retry. + */ +struct drm_modeset_acquire_ctx { + + struct ww_acquire_ctx ww_ctx; + + /* + * Contended lock: if a lock is contended you should only call + * drm_modeset_backoff() which drops locks and slow-locks the + * contended lock. + */ + struct drm_modeset_lock *contended; + + /* + * Stack depot for debugging when a contended lock was not backed off + * from. + */ + depot_stack_handle_t stack_depot; + + /* + * list of held locks (drm_modeset_lock) + */ + struct list_head locked; + + /* + * Trylock mode, use only for panic handlers! + */ + bool trylock_only; + + /* Perform interruptible waits on this context. */ + bool interruptible; +}; + +/** + * struct drm_modeset_lock - used for locking modeset resources. + * @mutex: resource locking + * @head: used to hold its place on &drm_atomi_state.locked list when + * part of an atomic update + * + * Used for locking CRTCs and other modeset resources. + */ +struct drm_modeset_lock { + /* + * modeset lock + */ + struct ww_mutex mutex; + + /* + * Resources that are locked as part of an atomic update are added + * to a list (so we know what to unlock at the end). + */ + struct list_head head; +}; + +#define DRM_MODESET_ACQUIRE_INTERRUPTIBLE BIT(0) + +void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx, + uint32_t flags); +void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx); +void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx *ctx); +int drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx); + +void drm_modeset_lock_init(struct drm_modeset_lock *lock); + +/** + * drm_modeset_lock_fini - cleanup lock + * @lock: lock to cleanup + */ +static inline void drm_modeset_lock_fini(struct drm_modeset_lock *lock) +{ + WARN_ON(!list_empty(&lock->head)); +} + +/** + * drm_modeset_is_locked - equivalent to mutex_is_locked() + * @lock: lock to check + */ +static inline bool drm_modeset_is_locked(struct drm_modeset_lock *lock) +{ + return ww_mutex_is_locked(&lock->mutex); +} + +/** + * drm_modeset_lock_assert_held - equivalent to lockdep_assert_held() + * @lock: lock to check + */ +static inline void drm_modeset_lock_assert_held(struct drm_modeset_lock *lock) +{ + lockdep_assert_held(&lock->mutex.base); +} + +int drm_modeset_lock(struct drm_modeset_lock *lock, + struct drm_modeset_acquire_ctx *ctx); +int __must_check drm_modeset_lock_single_interruptible(struct drm_modeset_lock *lock); +void drm_modeset_unlock(struct drm_modeset_lock *lock); + +struct drm_device; +struct drm_crtc; +struct drm_plane; + +void drm_modeset_lock_all(struct drm_device *dev); +void drm_modeset_unlock_all(struct drm_device *dev); +void drm_warn_on_modeset_not_all_locked(struct drm_device *dev); + +int drm_modeset_lock_all_ctx(struct drm_device *dev, + struct drm_modeset_acquire_ctx *ctx); + +/** + * DRM_MODESET_LOCK_ALL_BEGIN - Helper to acquire modeset locks + * @dev: drm device + * @ctx: local modeset acquire context, will be dereferenced + * @flags: DRM_MODESET_ACQUIRE_* flags to pass to drm_modeset_acquire_init() + * @ret: local ret/err/etc variable to track error status + * + * Use these macros to simplify grabbing all modeset locks using a local + * context. This has the advantage of reducing boilerplate, but also properly + * checking return values where appropriate. + * + * Any code run between BEGIN and END will be holding the modeset locks. + * + * This must be paired with DRM_MODESET_LOCK_ALL_END(). We will jump back and + * forth between the labels on deadlock and error conditions. + * + * Drivers can acquire additional modeset locks. If any lock acquisition + * fails, the control flow needs to jump to DRM_MODESET_LOCK_ALL_END() with + * the @ret parameter containing the return value of drm_modeset_lock(). + * + * Returns: + * The only possible value of ret immediately after DRM_MODESET_LOCK_ALL_BEGIN() + * is 0, so no error checking is necessary + */ +#define DRM_MODESET_LOCK_ALL_BEGIN(dev, ctx, flags, ret) \ + if (!drm_drv_uses_atomic_modeset(dev)) \ + mutex_lock(&dev->mode_config.mutex); \ + drm_modeset_acquire_init(&ctx, flags); \ +modeset_lock_retry: \ + ret = drm_modeset_lock_all_ctx(dev, &ctx); \ + if (ret) \ + goto modeset_lock_fail; + +/** + * DRM_MODESET_LOCK_ALL_END - Helper to release and cleanup modeset locks + * @dev: drm device + * @ctx: local modeset acquire context, will be dereferenced + * @ret: local ret/err/etc variable to track error status + * + * The other side of DRM_MODESET_LOCK_ALL_BEGIN(). It will bounce back to BEGIN + * if ret is -EDEADLK. + * + * It's important that you use the same ret variable for begin and end so + * deadlock conditions are properly handled. + * + * Returns: + * ret will be untouched unless it is -EDEADLK on entry. That means that if you + * successfully acquire the locks, ret will be whatever your code sets it to. If + * there is a deadlock or other failure with acquire or backoff, ret will be set + * to that failure. In both of these cases the code between BEGIN/END will not + * be run, so the failure will reflect the inability to grab the locks. + */ +#define DRM_MODESET_LOCK_ALL_END(dev, ctx, ret) \ +modeset_lock_fail: \ + if (ret == -EDEADLK) { \ + ret = drm_modeset_backoff(&ctx); \ + if (!ret) \ + goto modeset_lock_retry; \ + } \ + drm_modeset_drop_locks(&ctx); \ + drm_modeset_acquire_fini(&ctx); \ + if (!drm_drv_uses_atomic_modeset(dev)) \ + mutex_unlock(&dev->mode_config.mutex); + +#endif /* DRM_MODESET_LOCK_H_ */ |