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470fac3a17
consistantly. After a lengthy irc discussion it seems like we shouldn't need to worry about them, but it's nice to know about. MFC after: 3 days
200 lines
5.6 KiB
C
200 lines
5.6 KiB
C
/*-
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* Copyright 1999 Precision Insight, Inc., Cedar Park, Texas.
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* Copyright 2000 VA Linux Systems, Inc., Sunnyvale, California.
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* All Rights Reserved.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* VA LINUX SYSTEMS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
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* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
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* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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* OTHER DEALINGS IN THE SOFTWARE.
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*
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* Authors:
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* Rickard E. (Rik) Faith <faith@valinux.com>
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* Gareth Hughes <gareth@valinux.com>
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*
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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/** @file drm_lock.c
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* Implementation of the ioctls and other support code for dealing with the
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* hardware lock.
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*
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* The DRM hardware lock is a shared structure between the kernel and userland.
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*
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* On uncontended access where the new context was the last context, the
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* client may take the lock without dropping down into the kernel, using atomic
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* compare-and-set.
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*
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* If the client finds during compare-and-set that it was not the last owner
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* of the lock, it calls the DRM lock ioctl, which may sleep waiting for the
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* lock, and may have side-effects of kernel-managed context switching.
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*
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* When the client releases the lock, if the lock is marked as being contended
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* by another client, then the DRM unlock ioctl is called so that the
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* contending client may be woken up.
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*/
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#include "dev/drm/drmP.h"
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int drm_lock(struct drm_device *dev, void *data, struct drm_file *file_priv)
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{
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struct drm_lock *lock = data;
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int ret = 0;
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if (lock->context == DRM_KERNEL_CONTEXT) {
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DRM_ERROR("Process %d using kernel context %d\n",
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DRM_CURRENTPID, lock->context);
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return EINVAL;
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}
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DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
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lock->context, DRM_CURRENTPID, dev->lock.hw_lock->lock,
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lock->flags);
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if (drm_core_check_feature(dev, DRIVER_DMA_QUEUE) &&
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lock->context < 0)
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return EINVAL;
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DRM_LOCK();
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for (;;) {
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if (drm_lock_take(&dev->lock, lock->context)) {
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dev->lock.file_priv = file_priv;
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dev->lock.lock_time = jiffies;
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atomic_inc(&dev->counts[_DRM_STAT_LOCKS]);
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break; /* Got lock */
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}
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/* Contention */
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ret = mtx_sleep((void *)&dev->lock.lock_queue, &dev->dev_lock,
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PCATCH, "drmlk2", 0);
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if (ret != 0)
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break;
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}
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DRM_UNLOCK();
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if (ret == ERESTART)
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DRM_DEBUG("restarting syscall\n");
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else
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DRM_DEBUG("%d %s\n", lock->context,
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ret ? "interrupted" : "has lock");
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if (ret != 0)
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return ret;
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/* XXX: Add signal blocking here */
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if (dev->driver->dma_quiescent != NULL &&
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(lock->flags & _DRM_LOCK_QUIESCENT))
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dev->driver->dma_quiescent(dev);
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return 0;
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}
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int drm_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv)
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{
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struct drm_lock *lock = data;
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DRM_DEBUG("%d (pid %d) requests unlock (0x%08x), flags = 0x%08x\n",
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lock->context, DRM_CURRENTPID, dev->lock.hw_lock->lock,
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lock->flags);
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if (lock->context == DRM_KERNEL_CONTEXT) {
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DRM_ERROR("Process %d using kernel context %d\n",
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DRM_CURRENTPID, lock->context);
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return EINVAL;
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}
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atomic_inc(&dev->counts[_DRM_STAT_UNLOCKS]);
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DRM_LOCK();
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drm_lock_transfer(&dev->lock, DRM_KERNEL_CONTEXT);
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if (drm_lock_free(&dev->lock, DRM_KERNEL_CONTEXT)) {
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DRM_ERROR("\n");
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}
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DRM_UNLOCK();
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return 0;
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}
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int drm_lock_take(struct drm_lock_data *lock_data, unsigned int context)
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{
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volatile unsigned int *lock = &lock_data->hw_lock->lock;
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unsigned int old, new;
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do {
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old = *lock;
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if (old & _DRM_LOCK_HELD)
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new = old | _DRM_LOCK_CONT;
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else
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new = context | _DRM_LOCK_HELD;
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} while (!atomic_cmpset_int(lock, old, new));
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if (_DRM_LOCKING_CONTEXT(old) == context) {
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if (old & _DRM_LOCK_HELD) {
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if (context != DRM_KERNEL_CONTEXT) {
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DRM_ERROR("%d holds heavyweight lock\n",
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context);
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}
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return 0;
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}
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}
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if (new == (context | _DRM_LOCK_HELD)) {
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/* Have lock */
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return 1;
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}
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return 0;
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}
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/* This takes a lock forcibly and hands it to context. Should ONLY be used
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inside *_unlock to give lock to kernel before calling *_dma_schedule. */
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int drm_lock_transfer(struct drm_lock_data *lock_data, unsigned int context)
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{
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volatile unsigned int *lock = &lock_data->hw_lock->lock;
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unsigned int old, new;
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lock_data->file_priv = NULL;
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do {
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old = *lock;
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new = context | _DRM_LOCK_HELD;
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} while (!atomic_cmpset_int(lock, old, new));
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return 1;
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}
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int drm_lock_free(struct drm_lock_data *lock_data, unsigned int context)
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{
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volatile unsigned int *lock = &lock_data->hw_lock->lock;
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unsigned int old, new;
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lock_data->file_priv = NULL;
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do {
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old = *lock;
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new = 0;
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} while (!atomic_cmpset_int(lock, old, new));
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if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
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DRM_ERROR("%d freed heavyweight lock held by %d\n",
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context, _DRM_LOCKING_CONTEXT(old));
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return 1;
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}
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DRM_WAKEUP_INT((void *)&lock_data->lock_queue);
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return 0;
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}
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