drm/bsd-core/drm_lock.c

/* lock.c -- IOCTLs for locking -*- linux-c -*-
 * Created: Tue Feb  2 08:37:54 1999 by faith@valinux.com
 *
 * 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>
 *
 */

#include "drmP.h"

int DRM(lock_take)(__volatile__ unsigned int *lock, unsigned int context)
{
	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) {
		if (old & _DRM_LOCK_HELD) {
			if (context != DRM_KERNEL_CONTEXT) {
				DRM_ERROR("%d holds heavyweight lock\n",
					  context);
			}
			return 0;
		}
	}
	if (new == (context | _DRM_LOCK_HELD)) {
				/* Have lock */
		return 1;
	}
	return 0;
}

/* This takes a lock forcibly and hands it to context.	Should ONLY be used
   inside *_unlock to give lock to kernel before calling *_dma_schedule. */
int DRM(lock_transfer)(drm_device_t *dev,
		       __volatile__ unsigned int *lock, unsigned int context)
{
	unsigned int old, new;

	dev->lock.filp = NULL;
	do {
		old  = *lock;
		new  = context | _DRM_LOCK_HELD;
	} while (!atomic_cmpset_int(lock, old, new));

	return 1;
}

int DRM(lock_free)(drm_device_t *dev,
		   __volatile__ unsigned int *lock, unsigned int context)
{
	unsigned int old, new;

	dev->lock.filp = NULL;
	do {
		old  = *lock;
		new  = 0;
	} while (!atomic_cmpset_int(lock, old, new));

	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;
	}
	DRM_WAKEUP_INT((void *)&dev->lock.lock_queue);
	return 0;
}