From 3b19b50cb5cd31e60eb03e99dd1109b6d0f5b8a3 Mon Sep 17 00:00:00 2001 From: Thomas Hellstrom Date: Sun, 21 Oct 2007 12:20:56 +0200 Subject: Remove the need for the hardware lock in the buffer manager. Add interface entry cleaning a memory type without touching NO_EVICT buffers. --- linux-core/drm_bo_lock.c | 178 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 178 insertions(+) create mode 100644 linux-core/drm_bo_lock.c (limited to 'linux-core/drm_bo_lock.c') diff --git a/linux-core/drm_bo_lock.c b/linux-core/drm_bo_lock.c new file mode 100644 index 00000000..e5a86826 --- /dev/null +++ b/linux-core/drm_bo_lock.c @@ -0,0 +1,178 @@ +/************************************************************************** + * + * Copyright (c) 2007 Tungsten Graphics, Inc., Cedar Park, TX., USA + * All Rights Reserved. + * + * 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, sub license, 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 (including the + * next paragraph) 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 NON-INFRINGEMENT. IN NO EVENT SHALL + * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS 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. + * + **************************************************************************/ +/* + * Authors: Thomas Hellström + */ + +/* + * This file implements a simple replacement for the buffer manager use + * of the heavyweight hardware lock. + * The lock is a read-write lock. Taking it in read mode is fast, and + * intended for in-kernel use only. + * Taking it in write mode is slow. + * + * The write mode is used only when there is a need to block all + * user-space processes from allocating a + * new memory area. + * Typical use in write mode is X server VT switching, and it's allowed + * to leave kernel space with the write lock held. If a user-space process + * dies while having the write-lock, it will be released during the file + * descriptor release. + * + * The read lock is typically placed at the start of an IOCTL- or + * user-space callable function that may end up allocating a memory area. + * This includes setstatus, super-ioctls and no_pfn; the latter may move + * unmappable regions to mappable. It's a bug to leave kernel space with the + * read lock held. + * + * Both read- and write lock taking is interruptible for low signal-delivery + * latency. The locking functions will return -EAGAIN if interrupted by a + * signal. + * + * Locking order: The lock should be taken BEFORE any kernel mutexes + * or spinlocks. + */ + +#include "drmP.h" + +void drm_bo_init_lock(struct drm_bo_lock *lock) +{ + DRM_INIT_WAITQUEUE(&lock->queue); + atomic_set(&lock->write_lock_pending, 0); + atomic_set(&lock->readers, 0); +} + +void drm_bo_read_unlock(struct drm_bo_lock *lock) +{ + if (unlikely(atomic_add_negative(-1, &lock->readers))) + BUG(); + if (atomic_read(&lock->readers) == 0) + wake_up_interruptible(&lock->queue); +} + +EXPORT_SYMBOL(drm_bo_read_unlock); + +int drm_bo_read_lock(struct drm_bo_lock *lock) +{ + while (unlikely(atomic_read(&lock->write_lock_pending) != 0)) { + int ret; + ret = wait_event_interruptible + (lock->queue, atomic_read(&lock->write_lock_pending) == 0); + if (ret) + return -EAGAIN; + } + + while (unlikely(!atomic_add_unless(&lock->readers, 1, -1))) { + int ret; + ret = wait_event_interruptible + (lock->queue, atomic_add_unless(&lock->readers, 1, -1)); + if (ret) + return -EAGAIN; + } + return 0; +} + +EXPORT_SYMBOL(drm_bo_read_lock); + +static int __drm_bo_write_unlock(struct drm_bo_lock *lock) +{ + if (unlikely(atomic_cmpxchg(&lock->readers, -1, 0) != -1)) + return -EINVAL; + if (unlikely(atomic_cmpxchg(&lock->write_lock_pending, 1, 0) != 1)) + return -EINVAL; + wake_up_interruptible(&lock->queue); + return 0; +} + +static void drm_bo_write_lock_remove(struct drm_file *file_priv, + struct drm_user_object *item) +{ + struct drm_bo_lock *lock = container_of(item, struct drm_bo_lock, base); + int ret; + + ret = __drm_bo_write_unlock(lock); + BUG_ON(ret); +} + +int drm_bo_write_lock(struct drm_bo_lock *lock, struct drm_file *file_priv) +{ + int ret = 0; + struct drm_device *dev; + + if (unlikely(atomic_cmpxchg(&lock->write_lock_pending, 0, 1) != 0)) { + return -EINVAL; + } + + while (unlikely(atomic_cmpxchg(&lock->readers, 0, -1) != 0)) { + ret = wait_event_interruptible + (lock->queue, atomic_cmpxchg(&lock->readers, 0, -1) == 0); + + if (ret) { + atomic_set(&lock->write_lock_pending, 0); + wake_up_interruptible(&lock->queue); + return -EAGAIN; + } + } + + /* + * Add a dummy user-object, the destructor of which will + * make sure the lock is released if the client dies + * while holding it. + */ + + dev = file_priv->head->dev; + mutex_lock(&dev->struct_mutex); + ret = drm_add_user_object(file_priv, &lock->base, 0); + lock->base.remove = &drm_bo_write_lock_remove; + lock->base.type = drm_lock_type; + if (ret) { + (void)__drm_bo_write_unlock(lock); + } + mutex_unlock(&dev->struct_mutex); + + return ret; +} + +int drm_bo_write_unlock(struct drm_bo_lock *lock, struct drm_file *file_priv) +{ + struct drm_device *dev = file_priv->head->dev; + struct drm_ref_object *ro; + + mutex_lock(&dev->struct_mutex); + + if (lock->base.owner != file_priv) { + mutex_unlock(&dev->struct_mutex); + return -EINVAL; + } + ro = drm_lookup_ref_object(file_priv, &lock->base, _DRM_REF_USE); + BUG_ON(!ro); + drm_remove_ref_object(file_priv, ro); + lock->base.owner = NULL; + + mutex_unlock(&dev->struct_mutex); + return 0; +} -- cgit v1.2.3