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

     /*-
      * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
      *
      * Copyright (c) 2005 John Baldwin <jhb@FreeBSD.org>
      * Copyright (c) 2020 The FreeBSD Foundation
      *
      * Portions of this software were 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__
    
    #ifdef _KERNEL
    
    #include <sys/systm.h>
    #include <sys/_blockcount.h>
    
    struct lock_object;
    
    int _blockcount_sleep(blockcount_t *bc, struct lock_object *, const char *wmesg,
        int prio);
    void _blockcount_wakeup(blockcount_t *bc, u_int old);
    
    static __inline void
    blockcount_init(blockcount_t *bc)
    {
            atomic_store_int(&bc->__count, 0);
    }
    
    static __inline void
    blockcount_acquire(blockcount_t *bc, u_int n)
    {
    #ifdef INVARIANTS
            u_int old;
    
            old = atomic_fetchadd_int(&bc->__count, n);
            KASSERT(old + n > old, ("%s: counter overflow %p", __func__, bc));
    #else
            atomic_add_int(&bc->__count, n);
    #endif
    }
    
    static __inline void
    blockcount_release(blockcount_t *bc, u_int n)
    {
            u_int old;
    
            atomic_thread_fence_rel();
            old = atomic_fetchadd_int(&bc->__count, -n);
            KASSERT(old >= n, ("%s: counter underflow %p", __func__, bc));
            if (_BLOCKCOUNT_COUNT(old) == n && _BLOCKCOUNT_WAITERS(old))
                    _blockcount_wakeup(bc, old);
    }
    
    static __inline void
    _blockcount_wait(blockcount_t *bc, struct lock_object *lo, const char *wmesg,
        int prio)
    {
            KASSERT((prio & ~PRIMASK) == 0, ("%s: invalid prio %x", __func__, prio));
    
            while (_blockcount_sleep(bc, lo, wmesg, prio) == EAGAIN)
                    ;
    }
    
    #define blockcount_sleep(bc, lo, wmesg, prio)   \
            _blockcount_sleep((bc), (struct lock_object *)(lo), (wmesg), (prio))
    #define blockcount_wait(bc, lo, wmesg, prio)    \
            _blockcount_wait((bc), (struct lock_object *)(lo), (wmesg), (prio))
    
    #endif /* _KERNEL */
    #endif /* !__SYS_BLOCKCOUNT_H__ */

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