efb/src/drm_lock.c

/*
 * Copyright (c) 2006, 2008, Oracle and/or its affiliates. All rights reserved.
 */

/*
 * 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(drm_lock_data_t *lock_data, unsigned int context)
{
    unsigned int old, new, prev;
    volatile unsigned int *lock = &lock_data->hw_lock->lock;

    do {
        old = *lock;
        if (old & _DRM_LOCK_HELD)
            new = old | _DRM_LOCK_CONT;
        else
            new = context | _DRM_LOCK_HELD;
        prev = atomic_cas_uint(lock, old, new);
    } while (prev != old);

    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 ((_DRM_LOCKING_CONTEXT(new)) == context &&
        _DRM_LOCK_IS_HELD(new)) {
                /* 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, prev;

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

    return (1);
}

int
drm_lock_free(drm_device_t *dev, volatile unsigned int *lock,
    unsigned int context)
{
    unsigned int old, new, prev;

    mutex_enter(&(dev->lock.lock_mutex));
    dev->lock.filp = NULL;
    do {
        old  = *lock;
        new = 0;
        prev = atomic_cas_uint(lock, old, new);
    } while (prev != old);

    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));
        mutex_exit(&(dev->lock.lock_mutex));
        return (1);
    }
    cv_broadcast(&(dev->lock.lock_cv));
    mutex_exit(&(dev->lock.lock_mutex));
    return (0);
}

/*ARGSUSED*/
int
drm_lock(DRM_IOCTL_ARGS)
{
    DRM_DEVICE;
    drm_lock_t lock;
    int ret = 0;

    DRM_COPYFROM_WITH_RETURN(&lock, (void *)data, sizeof (lock));

    if (lock.context == DRM_KERNEL_CONTEXT) {
        return (EINVAL);
    }

    if (dev->driver->use_dma_queue && lock.context < 0)
        return (EINVAL);

    mutex_enter(&(dev->lock.lock_mutex));
    for (;;) {
        if (drm_lock_take(&dev->lock, lock.context)) {
            dev->lock.filp = fpriv;
            dev->lock.lock_time = jiffies;
            break;  /* Got lock */
        }
        ret = cv_wait_sig(&(dev->lock.lock_cv),
            &(dev->lock.lock_mutex));

        if (ret == 0) {
            mutex_exit(&(dev->lock.lock_mutex));
            return (EINTR);
        }
    }
    mutex_exit(&(dev->lock.lock_mutex));

    if (dev->driver->dma_quiescent != NULL &&
        (lock.flags & _DRM_LOCK_QUIESCENT))
        dev->driver->dma_quiescent(dev);

    return (0);
}

/*ARGSUSED*/
int
drm_unlock(DRM_IOCTL_ARGS)
{
    DRM_DEVICE;
    drm_lock_t lock;

    DRM_COPYFROM_WITH_RETURN(&lock, (void *)data, sizeof (lock));

    if (lock.context == DRM_KERNEL_CONTEXT) {
        DRM_ERROR("Process %d using kernel context %d\n",
            DRM_CURRENTPID, lock.context);
        return (EINVAL);
    }
    atomic_inc_32(&dev->counts[_DRM_STAT_UNLOCKS]);

    DRM_LOCK();
    if (drm_lock_free(dev, &dev->lock.hw_lock->lock, lock.context)) {
        DRM_ERROR("drm_unlock\n");
    }
    DRM_UNLOCK();
    return (0);
}