FreeBSD/Linux Kernel Cross Reference
sys/sys/_blockcount.h

     /*-
      * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
      *
      * Copyright (c) 2020 The FreeBSD Foundation
      *
      * This software was developed by Mark Johnston under sponsorship from
      * the FreeBSD Foundation.
      *
      * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions are
     * met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in
     *    the documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     * $FreeBSD$
     */
    
    #ifndef __SYS__BLOCKCOUNT_H__
    #define __SYS__BLOCKCOUNT_H__
    
    #include <machine/atomic.h>
    
    typedef struct _blockcount {
            unsigned int    __count;
    } blockcount_t;
    
    #define _BLOCKCOUNT_WAITERS_FLAG        (1U << 31)
    #define _BLOCKCOUNT_COUNT(c)            ((c) & ~_BLOCKCOUNT_WAITERS_FLAG)
    #define _BLOCKCOUNT_WAITERS(c)          (((c) & _BLOCKCOUNT_WAITERS_FLAG) != 0)
    
    static inline unsigned int
    blockcount_read(blockcount_t *count)
    {
            return (_BLOCKCOUNT_COUNT(atomic_load_int(&count->__count)));
    }
    
    #endif /* !__SYS__BLOCKCOUNT_H__ */

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