refcount.h

Version: - FREEBSD - FREEBSD-13-STABLE - FREEBSD-13-0 - FREEBSD-12-STABLE - FREEBSD-12-0 - FREEBSD-11-STABLE - FREEBSD-11-0 - FREEBSD-10-STABLE - FREEBSD-10-0 - FREEBSD-9-STABLE - FREEBSD-9-0 - FREEBSD-8-STABLE - FREEBSD-8-0 - FREEBSD-7-STABLE - FREEBSD-7-0 - FREEBSD-6-STABLE - FREEBSD-6-0 - FREEBSD-5-STABLE - FREEBSD-5-0 - FREEBSD-4-STABLE - FREEBSD-3-STABLE - FREEBSD22 - l41 - OPENBSD - linux-2.6 - MK84 - PLAN9 - xnu-8792
SearchContext: - none - 3 - 10

    1 /*-
    2  * Copyright (c) 2005 John Baldwin <jhb@FreeBSD.org>
    3  *
    4  * Redistribution and use in source and binary forms, with or without
    5  * modification, are permitted provided that the following conditions
    6  * are met:
    7  * 1. Redistributions of source code must retain the above copyright
    8  *    notice, this list of conditions and the following disclaimer.
    9  * 2. Redistributions in binary form must reproduce the above copyright
   10  *    notice, this list of conditions and the following disclaimer in the
   11  *    documentation and/or other materials provided with the distribution.
   12  *
   13  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   14  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   16  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   17  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   18  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   19  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   20  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   21  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   22  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   23  * SUCH DAMAGE.
   24  *
   25  * $FreeBSD$
   26  */
   27 
   28 #ifndef __SYS_REFCOUNT_H__
   29 #define __SYS_REFCOUNT_H__
   30 
   31 #include <sys/limits.h>
   32 #include <machine/atomic.h>
   33 
   34 #ifdef _KERNEL
   35 #include <sys/systm.h>
   36 #else
   37 #define KASSERT(exp, msg)       /* */
   38 #endif
   39 
   40 static __inline void
   41 refcount_init(volatile u_int *count, u_int value)
   42 {
   43 
   44         *count = value;
   45 }
   46 
   47 static __inline void
   48 refcount_acquire(volatile u_int *count)
   49 {
   50 
   51         KASSERT(*count < UINT_MAX, ("refcount %p overflowed", count));
   52         atomic_add_int(count, 1);
   53 }
   54 
   55 static __inline int
   56 refcount_release(volatile u_int *count)
   57 {
   58         u_int old;
   59 
   60         atomic_thread_fence_rel();
   61         old = atomic_fetchadd_int(count, -1);
   62         KASSERT(old > 0, ("refcount %p is zero", count));
   63         if (old > 1)
   64                 return (0);
   65 
   66         /*
   67          * Last reference.  Signal the user to call the destructor.
   68          *
   69          * Ensure that the destructor sees all updates.  The fence_rel
   70          * at the start of the function synchronized with this fence.
   71          */
   72         atomic_thread_fence_acq();
   73         return (1);
   74 }
   75 
   76 /*
   77  * This functions returns non-zero if the refcount was
   78  * incremented. Else zero is returned.
   79  *
   80  * A temporary hack until refcount_* APIs are sorted out.
   81  */
   82 static __inline __result_use_check int
   83 refcount_acquire_if_not_zero(volatile u_int *count)
   84 {
   85         u_int old;
   86 
   87         old = *count;
   88         for (;;) {
   89                 KASSERT(old < UINT_MAX, ("refcount %p overflowed", count));
   90                 if (old == 0)
   91                         return (0);
   92                 if (atomic_fcmpset_int(count, &old, old + 1))
   93                         return (1);
   94         }
   95 }
   96 
   97 static __inline __result_use_check int
   98 refcount_release_if_not_last(volatile u_int *count)
   99 {
  100         u_int old;
  101 
  102         old = *count;
  103         for (;;) {
  104                 KASSERT(old > 0, ("refcount %p is zero", count));
  105                 if (old == 1)
  106                         return (0);
  107                 if (atomic_fcmpset_int(count, &old, old - 1))
  108                         return (1);
  109         }
  110 }
  111 
  112 #endif  /* ! __SYS_REFCOUNT_H__ */

Cache object: 599f9bbf3f696029ba79e6eb38868cf6

[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]

This page is part of the FreeBSD/Linux Linux Kernel Cross-Reference, and was automatically generated using a modified version of the LXR engine.

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

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