diff options
Diffstat (limited to 'kernel/drivers/gpu/drm/drm_modeset_lock.c')
| -rw-r--r-- | kernel/drivers/gpu/drm/drm_modeset_lock.c | 482 |
1 files changed, 482 insertions, 0 deletions
diff --git a/kernel/drivers/gpu/drm/drm_modeset_lock.c b/kernel/drivers/gpu/drm/drm_modeset_lock.c new file mode 100644 index 000000000..51cc47d82 --- /dev/null +++ b/kernel/drivers/gpu/drm/drm_modeset_lock.c @@ -0,0 +1,482 @@ +/* + * 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. + */ + +#include <drm/drmP.h> +#include <drm/drm_crtc.h> +#include <drm/drm_modeset_lock.h> + +/** + * DOC: kms locking + * + * As KMS moves toward more fine grained locking, and atomic ioctl where + * userspace can indirectly control locking order, it becomes necessary + * to use ww_mutex and acquire-contexts to avoid deadlocks. But because + * the locking is more distributed around the driver code, we want a bit + * of extra utility/tracking out of our acquire-ctx. This is provided + * by drm_modeset_lock / drm_modeset_acquire_ctx. + * + * For basic principles of ww_mutex, see: Documentation/locking/ww-mutex-design.txt + * + * The basic usage pattern is to: + * + * drm_modeset_acquire_init(&ctx) + * retry: + * foreach (lock in random_ordered_set_of_locks) { + * ret = drm_modeset_lock(lock, &ctx) + * if (ret == -EDEADLK) { + * drm_modeset_backoff(&ctx); + * goto retry; + * } + * } + * + * ... do stuff ... + * + * drm_modeset_drop_locks(&ctx); + * drm_modeset_acquire_fini(&ctx); + */ + + +/** + * __drm_modeset_lock_all - internal helper to grab all modeset locks + * @dev: DRM device + * @trylock: trylock mode for atomic contexts + * + * This is a special version of drm_modeset_lock_all() which can also be used in + * atomic contexts. Then @trylock must be set to true. + * + * Returns: + * 0 on success or negative error code on failure. + */ +int __drm_modeset_lock_all(struct drm_device *dev, + bool trylock) +{ + struct drm_mode_config *config = &dev->mode_config; + struct drm_modeset_acquire_ctx *ctx; + int ret; + + ctx = kzalloc(sizeof(*ctx), + trylock ? GFP_ATOMIC : GFP_KERNEL); + if (!ctx) + return -ENOMEM; + + if (trylock) { + if (!mutex_trylock(&config->mutex)) + return -EBUSY; + } else { + mutex_lock(&config->mutex); + } + + drm_modeset_acquire_init(ctx, 0); + ctx->trylock_only = trylock; + +retry: + ret = drm_modeset_lock(&config->connection_mutex, ctx); + if (ret) + goto fail; + ret = drm_modeset_lock_all_crtcs(dev, ctx); + if (ret) + goto fail; + + WARN_ON(config->acquire_ctx); + + /* now we hold the locks, so now that it is safe, stash the + * ctx for drm_modeset_unlock_all(): + */ + config->acquire_ctx = ctx; + + drm_warn_on_modeset_not_all_locked(dev); + + return 0; + +fail: + if (ret == -EDEADLK) { + drm_modeset_backoff(ctx); + goto retry; + } + + return ret; +} +EXPORT_SYMBOL(__drm_modeset_lock_all); + +/** + * drm_modeset_lock_all - take all modeset locks + * @dev: drm device + * + * This function takes all modeset locks, suitable where a more fine-grained + * scheme isn't (yet) implemented. Locks must be dropped with + * drm_modeset_unlock_all. + */ +void drm_modeset_lock_all(struct drm_device *dev) +{ + WARN_ON(__drm_modeset_lock_all(dev, false) != 0); +} +EXPORT_SYMBOL(drm_modeset_lock_all); + +/** + * drm_modeset_unlock_all - drop all modeset locks + * @dev: device + * + * This function drop all modeset locks taken by drm_modeset_lock_all. + */ +void drm_modeset_unlock_all(struct drm_device *dev) +{ + struct drm_mode_config *config = &dev->mode_config; + struct drm_modeset_acquire_ctx *ctx = config->acquire_ctx; + + if (WARN_ON(!ctx)) + return; + + config->acquire_ctx = NULL; + drm_modeset_drop_locks(ctx); + drm_modeset_acquire_fini(ctx); + + kfree(ctx); + + mutex_unlock(&dev->mode_config.mutex); +} +EXPORT_SYMBOL(drm_modeset_unlock_all); + +/** + * drm_modeset_lock_crtc - lock crtc with hidden acquire ctx for a plane update + * @crtc: DRM CRTC + * @plane: DRM plane to be updated on @crtc + * + * This function locks the given crtc and plane (which should be either the + * primary or cursor plane) using a hidden acquire context. This is necessary so + * that drivers internally using the atomic interfaces can grab further locks + * with the lock acquire context. + * + * Note that @plane can be NULL, e.g. when the cursor support hasn't yet been + * converted to universal planes yet. + */ +void drm_modeset_lock_crtc(struct drm_crtc *crtc, + struct drm_plane *plane) +{ + struct drm_modeset_acquire_ctx *ctx; + int ret; + + ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); + if (WARN_ON(!ctx)) + return; + + drm_modeset_acquire_init(ctx, 0); + +retry: + ret = drm_modeset_lock(&crtc->mutex, ctx); + if (ret) + goto fail; + + if (plane) { + ret = drm_modeset_lock(&plane->mutex, ctx); + if (ret) + goto fail; + + if (plane->crtc) { + ret = drm_modeset_lock(&plane->crtc->mutex, ctx); + if (ret) + goto fail; + } + } + + WARN_ON(crtc->acquire_ctx); + + /* now we hold the locks, so now that it is safe, stash the + * ctx for drm_modeset_unlock_crtc(): + */ + crtc->acquire_ctx = ctx; + + return; + +fail: + if (ret == -EDEADLK) { + drm_modeset_backoff(ctx); + goto retry; + } +} +EXPORT_SYMBOL(drm_modeset_lock_crtc); + +/** + * drm_modeset_legacy_acquire_ctx - find acquire ctx for legacy ioctls + * @crtc: drm crtc + * + * Legacy ioctl operations like cursor updates or page flips only have per-crtc + * locking, and store the acquire ctx in the corresponding crtc. All other + * legacy operations take all locks and use a global acquire context. This + * function grabs the right one. + */ +struct drm_modeset_acquire_ctx * +drm_modeset_legacy_acquire_ctx(struct drm_crtc *crtc) +{ + if (crtc->acquire_ctx) + return crtc->acquire_ctx; + + WARN_ON(!crtc->dev->mode_config.acquire_ctx); + + return crtc->dev->mode_config.acquire_ctx; +} +EXPORT_SYMBOL(drm_modeset_legacy_acquire_ctx); + +/** + * drm_modeset_unlock_crtc - drop crtc lock + * @crtc: drm crtc + * + * This drops the crtc lock acquire with drm_modeset_lock_crtc() and all other + * locks acquired through the hidden context. + */ +void drm_modeset_unlock_crtc(struct drm_crtc *crtc) +{ + struct drm_modeset_acquire_ctx *ctx = crtc->acquire_ctx; + + if (WARN_ON(!ctx)) + return; + + crtc->acquire_ctx = NULL; + drm_modeset_drop_locks(ctx); + drm_modeset_acquire_fini(ctx); + + kfree(ctx); +} +EXPORT_SYMBOL(drm_modeset_unlock_crtc); + +/** + * drm_warn_on_modeset_not_all_locked - check that all modeset locks are locked + * @dev: device + * + * Useful as a debug assert. + */ +void drm_warn_on_modeset_not_all_locked(struct drm_device *dev) +{ + struct drm_crtc *crtc; + + /* Locking is currently fubar in the panic handler. */ + if (oops_in_progress) + return; + + list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) + WARN_ON(!drm_modeset_is_locked(&crtc->mutex)); + + WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex)); + WARN_ON(!mutex_is_locked(&dev->mode_config.mutex)); +} +EXPORT_SYMBOL(drm_warn_on_modeset_not_all_locked); + +/** + * drm_modeset_acquire_init - initialize acquire context + * @ctx: the acquire context + * @flags: for future + */ +void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx, + uint32_t flags) +{ + memset(ctx, 0, sizeof(*ctx)); + ww_acquire_init(&ctx->ww_ctx, &crtc_ww_class); + INIT_LIST_HEAD(&ctx->locked); +} +EXPORT_SYMBOL(drm_modeset_acquire_init); + +/** + * drm_modeset_acquire_fini - cleanup acquire context + * @ctx: the acquire context + */ +void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx) +{ + ww_acquire_fini(&ctx->ww_ctx); +} +EXPORT_SYMBOL(drm_modeset_acquire_fini); + +/** + * drm_modeset_drop_locks - drop all locks + * @ctx: the acquire context + * + * Drop all locks currently held against this acquire context. + */ +void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx *ctx) +{ + WARN_ON(ctx->contended); + while (!list_empty(&ctx->locked)) { + struct drm_modeset_lock *lock; + + lock = list_first_entry(&ctx->locked, + struct drm_modeset_lock, head); + + drm_modeset_unlock(lock); + } +} +EXPORT_SYMBOL(drm_modeset_drop_locks); + +static inline int modeset_lock(struct drm_modeset_lock *lock, + struct drm_modeset_acquire_ctx *ctx, + bool interruptible, bool slow) +{ + int ret; + + WARN_ON(ctx->contended); + + if (ctx->trylock_only) { + if (!ww_mutex_trylock(&lock->mutex)) + return -EBUSY; + else + return 0; + } else if (interruptible && slow) { + ret = ww_mutex_lock_slow_interruptible(&lock->mutex, &ctx->ww_ctx); + } else if (interruptible) { + ret = ww_mutex_lock_interruptible(&lock->mutex, &ctx->ww_ctx); + } else if (slow) { + ww_mutex_lock_slow(&lock->mutex, &ctx->ww_ctx); + ret = 0; + } else { + ret = ww_mutex_lock(&lock->mutex, &ctx->ww_ctx); + } + if (!ret) { + WARN_ON(!list_empty(&lock->head)); + list_add(&lock->head, &ctx->locked); + } else if (ret == -EALREADY) { + /* we already hold the lock.. this is fine. For atomic + * we will need to be able to drm_modeset_lock() things + * without having to keep track of what is already locked + * or not. + */ + ret = 0; + } else if (ret == -EDEADLK) { + ctx->contended = lock; + } + + return ret; +} + +static int modeset_backoff(struct drm_modeset_acquire_ctx *ctx, + bool interruptible) +{ + struct drm_modeset_lock *contended = ctx->contended; + + ctx->contended = NULL; + + if (WARN_ON(!contended)) + return 0; + + drm_modeset_drop_locks(ctx); + + return modeset_lock(contended, ctx, interruptible, true); +} + +/** + * drm_modeset_backoff - deadlock avoidance backoff + * @ctx: the acquire context + * + * If deadlock is detected (ie. drm_modeset_lock() returns -EDEADLK), + * you must call this function to drop all currently held locks and + * block until the contended lock becomes available. + */ +void drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx) +{ + modeset_backoff(ctx, false); +} +EXPORT_SYMBOL(drm_modeset_backoff); + +/** + * drm_modeset_backoff_interruptible - deadlock avoidance backoff + * @ctx: the acquire context + * + * Interruptible version of drm_modeset_backoff() + */ +int drm_modeset_backoff_interruptible(struct drm_modeset_acquire_ctx *ctx) +{ + return modeset_backoff(ctx, true); +} +EXPORT_SYMBOL(drm_modeset_backoff_interruptible); + +/** + * drm_modeset_lock - take modeset lock + * @lock: lock to take + * @ctx: acquire ctx + * + * If ctx is not NULL, then its ww acquire context is used and the + * lock will be tracked by the context and can be released by calling + * drm_modeset_drop_locks(). If -EDEADLK is returned, this means a + * deadlock scenario has been detected and it is an error to attempt + * to take any more locks without first calling drm_modeset_backoff(). + */ +int drm_modeset_lock(struct drm_modeset_lock *lock, + struct drm_modeset_acquire_ctx *ctx) +{ + if (ctx) + return modeset_lock(lock, ctx, false, false); + + ww_mutex_lock(&lock->mutex, NULL); + return 0; +} +EXPORT_SYMBOL(drm_modeset_lock); + +/** + * drm_modeset_lock_interruptible - take modeset lock + * @lock: lock to take + * @ctx: acquire ctx + * + * Interruptible version of drm_modeset_lock() + */ +int drm_modeset_lock_interruptible(struct drm_modeset_lock *lock, + struct drm_modeset_acquire_ctx *ctx) +{ + if (ctx) + return modeset_lock(lock, ctx, true, false); + + return ww_mutex_lock_interruptible(&lock->mutex, NULL); +} +EXPORT_SYMBOL(drm_modeset_lock_interruptible); + +/** + * drm_modeset_unlock - drop modeset lock + * @lock: lock to release + */ +void drm_modeset_unlock(struct drm_modeset_lock *lock) +{ + list_del_init(&lock->head); + ww_mutex_unlock(&lock->mutex); +} +EXPORT_SYMBOL(drm_modeset_unlock); + +/* In some legacy codepaths it's convenient to just grab all the crtc and plane + * related locks. */ +int drm_modeset_lock_all_crtcs(struct drm_device *dev, + struct drm_modeset_acquire_ctx *ctx) +{ + struct drm_mode_config *config = &dev->mode_config; + struct drm_crtc *crtc; + struct drm_plane *plane; + int ret = 0; + + list_for_each_entry(crtc, &config->crtc_list, head) { + ret = drm_modeset_lock(&crtc->mutex, ctx); + if (ret) + return ret; + } + + list_for_each_entry(plane, &config->plane_list, head) { + ret = drm_modeset_lock(&plane->mutex, ctx); + if (ret) + return ret; + } + + return 0; +} +EXPORT_SYMBOL(drm_modeset_lock_all_crtcs); |