/home/hillier_g/checkout/most4linux/most-kernel/rtseqlock.h

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/*
 *  Copyright(c) Siemens AG, Muenchen, Germany, 2005, 2006, 2007
 *                           Bernhard Walle <bernhard.walle@gmx.de>
 *                           Gernot Hillier <gernot.hillier@siemens.com>
 *
 * ----------------------------------------------------------------------------
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as 
 * published by the Free Software Foundation;
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 * ----------------------------------------------------------------------------
 */
#ifndef RTSEQLOCK_H
#define RTSEQLOCK_H

#ifdef HAVE_CONFIG_H
#include "config/config.h"
#endif
#include <asm/system.h>
#include <rtdm/rtdm_driver.h>

typedef struct {
    unsigned int        sequence;       
    rtdm_lock_t         lock;           
} rt_seqlock_t;

#define RT_SEQLOCK_UNLOCKED { 0, RTDM_LOCK_UNLOCKED }

#define rt_seqlock_init(x)                                          \
    do {                                                            \
        *(x) = (rt_seqlock_t)RT_SEQLOCK_UNLOCKED;                   \
    } while (0)

static inline void rt_write_seqlock(seqlock_t *sl)
{
    rtdm_lock_get(&sl->lock);
    ++sl->sequence;
    smp_wmb();
}

static inline void rt_write_sequnlock(seqlock_t *sl) 
{
    smp_wmb();
    sl->sequence++;
    rtdm_lock_put(&sl->lock);
}

static inline unsigned int rt_read_seqbegin(const seqlock_t *sl)
{
    unsigned ret = sl->sequence;
    smp_rmb();
    return ret;
}

static inline int rt_read_seqretry(const seqlock_t *sl, unsigned int iv)
{
    smp_rmb();
    return (iv & 1) | (sl->sequence ^ iv);
}

#define rt_write_seqlock_irqsave(sl, flags)                         \
    do {                                                            \
        rtdm_lock_get_irqsave(&sl->lock, flags);                    \
        ++sl->sequence;                                             \
        smp_wmb();                                                  \
    } while (0)


#define rt_write_sequnlock_irqrestore(sl, flags)                    \
    do {                                                            \
        smp_wmb();                                                  \
        sl->sequence++;                                             \
        rtdm_lock_put_irqrestore(&sl->lock, flags);                 \
    } while (0)


#endif /* RTSEQLOCK_H */

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