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/* $OpenBSD: drm_lock.c,v 1.17 2011/06/02 18:22:00 weerd Exp $ */
/*-
* Copyright 1999 Precision Insight, Inc., Cedar Park, Texas.
* Copyright 2000 VA Linux Systems, Inc., Sunnyvale, California.
* 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, 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 (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 NONINFRINGEMENT. IN NO EVENT SHALL
* VA LINUX SYSTEMS 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:
* Rickard E. (Rik) Faith <faith@valinux.com>
* Gareth Hughes <gareth@valinux.com>
*
*/
/** @file drm_lock.c
* Implementation of the ioctls and other support code for dealing with the
* hardware lock.
*
* The DRM hardware lock is a shared structure between the kernel and userland.
*
* On uncontended access where the new context was the last context, the
* client may take the lock without dropping down into the kernel, using atomic
* compare-and-set.
*
* If the client finds during compare-and-set that it was not the last owner
* of the lock, it calls the DRM lock ioctl, which may sleep waiting for the
* lock, and may have side-effects of kernel-managed context switching.
*
* When the client releases the lock, if the lock is marked as being contended
* by another client, then the DRM unlock ioctl is called so that the
* contending client may be woken up.
*/
#include "drmP.h"
int
drm_lock_take(struct drm_lock_data *lock_data, unsigned int context)
{
volatile unsigned int *lock = &lock_data->hw_lock->lock;
unsigned int old, new;
do {
old = *lock;
if (old & _DRM_LOCK_HELD)
new = old | _DRM_LOCK_CONT;
else
new = context | _DRM_LOCK_HELD;
} while (!atomic_cmpset_int(lock, old, new));
if (_DRM_LOCKING_CONTEXT(old) == context && _DRM_LOCK_IS_HELD(old)) {
if (context != DRM_KERNEL_CONTEXT)
DRM_ERROR("%d holds heavyweight lock\n", context);
return (0);
}
/* If the lock wasn't held before, it's ours */
return (!_DRM_LOCK_IS_HELD(old));
}
int
drm_lock_free(struct drm_lock_data *lock_data, unsigned int context)
{
volatile unsigned int *lock = &lock_data->hw_lock->lock;
unsigned int old, new;
mtx_enter(&lock_data->spinlock);
lock_data->file_priv = NULL;
do {
old = *lock;
new = 0;
} while (!atomic_cmpset_int(lock, old, new));
mtx_leave(&lock_data->spinlock);
if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
DRM_ERROR("%d freed heavyweight lock held by %d\n",
context, _DRM_LOCKING_CONTEXT(old));
return 1;
}
wakeup(lock_data);
return 0;
}
int
drm_lock(struct drm_device *dev, void *data, struct drm_file *file_priv)
{
struct drm_lock *lock = data;
int ret = 0;
if (lock->context == DRM_KERNEL_CONTEXT) {
DRM_ERROR("Process %d using kernel context %d\n",
DRM_CURRENTPID, lock->context);
return EINVAL;
}
DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
lock->context, DRM_CURRENTPID, dev->lock.hw_lock->lock,
lock->flags);
mtx_enter(&dev->lock.spinlock);
for (;;) {
if (drm_lock_take(&dev->lock, lock->context)) {
dev->lock.file_priv = file_priv;
break; /* Got lock */
}
/* Contention */
ret = msleep(&dev->lock, &dev->lock.spinlock,
PZERO | PCATCH, "drmlkq", 0);
if (ret != 0)
break;
}
mtx_leave(&dev->lock.spinlock);
DRM_DEBUG("%d %s\n", lock->context, ret ? "interrupted" : "has lock");
if (ret != 0)
return ret;
/* XXX: Add signal blocking here */
return 0;
}
int
drm_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv)
{
struct drm_lock *lock = data;
if (lock->context == DRM_KERNEL_CONTEXT) {
DRM_ERROR("Process %d using kernel context %d\n",
DRM_CURRENTPID, lock->context);
return EINVAL;
}
/* Check that the context unlock being requested actually matches
* who currently holds the lock.
*/
if (!_DRM_LOCK_IS_HELD(dev->lock.hw_lock->lock) ||
_DRM_LOCKING_CONTEXT(dev->lock.hw_lock->lock) != lock->context)
return EINVAL;
if (drm_lock_free(&dev->lock, lock->context)) {
DRM_ERROR("\n");
}
return 0;
}
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