1150629Sjhb/*- 2150629Sjhb * Copyright (c) 2005 John Baldwin <jhb@FreeBSD.org> 3150629Sjhb * 4150629Sjhb * Redistribution and use in source and binary forms, with or without 5150629Sjhb * modification, are permitted provided that the following conditions 6150629Sjhb * are met: 7150629Sjhb * 1. Redistributions of source code must retain the above copyright 8150629Sjhb * notice, this list of conditions and the following disclaimer. 9150629Sjhb * 2. Redistributions in binary form must reproduce the above copyright 10150629Sjhb * notice, this list of conditions and the following disclaimer in the 11150629Sjhb * documentation and/or other materials provided with the distribution. 12150629Sjhb * 13150629Sjhb * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 14150629Sjhb * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15150629Sjhb * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16150629Sjhb * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 17150629Sjhb * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18150629Sjhb * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19150629Sjhb * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20150629Sjhb * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21150629Sjhb * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22150629Sjhb * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23150629Sjhb * SUCH DAMAGE. 24150629Sjhb * 25150629Sjhb * $FreeBSD: stable/11/sys/sys/refcount.h 367457 2020-11-07 18:10:59Z dim $ 26150629Sjhb */ 27150629Sjhb 28150629Sjhb#ifndef __SYS_REFCOUNT_H__ 29150629Sjhb#define __SYS_REFCOUNT_H__ 30150629Sjhb 31238828Sglebius#include <sys/limits.h> 32180762Sdes#include <machine/atomic.h> 33180762Sdes 34180762Sdes#ifdef _KERNEL 35180762Sdes#include <sys/systm.h> 36180762Sdes#else 37180762Sdes#define KASSERT(exp, msg) /* */ 38180762Sdes#endif 39180762Sdes 40150629Sjhbstatic __inline void 41150629Sjhbrefcount_init(volatile u_int *count, u_int value) 42150629Sjhb{ 43150629Sjhb 44150629Sjhb *count = value; 45150629Sjhb} 46150629Sjhb 47150629Sjhbstatic __inline void 48150629Sjhbrefcount_acquire(volatile u_int *count) 49150629Sjhb{ 50150629Sjhb 51238828Sglebius KASSERT(*count < UINT_MAX, ("refcount %p overflowed", count)); 52320981Skib atomic_add_int(count, 1); 53150629Sjhb} 54150629Sjhb 55150629Sjhbstatic __inline int 56150629Sjhbrefcount_release(volatile u_int *count) 57150629Sjhb{ 58180762Sdes u_int old; 59150629Sjhb 60320981Skib atomic_thread_fence_rel(); 61180762Sdes old = atomic_fetchadd_int(count, -1); 62339862Shselasky KASSERT(old > 0, ("refcount %p is zero", count)); 63320981Skib if (old > 1) 64320981Skib return (0); 65320981Skib 66320981Skib /* 67320981Skib * Last reference. Signal the user to call the destructor. 68320981Skib * 69320981Skib * Ensure that the destructor sees all updates. The fence_rel 70320981Skib * at the start of the function synchronized with this fence. 71320981Skib */ 72320981Skib atomic_thread_fence_acq(); 73320981Skib return (1); 74150629Sjhb} 75150629Sjhb 76332755Savg/* 77339862Shselasky * This functions returns non-zero if the refcount was 78339862Shselasky * incremented. Else zero is returned. 79339862Shselasky * 80332755Savg * A temporary hack until refcount_* APIs are sorted out. 81332755Savg */ 82339862Shselaskystatic __inline __result_use_check int 83332755Savgrefcount_acquire_if_not_zero(volatile u_int *count) 84332755Savg{ 85332755Savg u_int old; 86332755Savg 87332755Savg old = *count; 88332755Savg for (;;) { 89339862Shselasky KASSERT(old < UINT_MAX, ("refcount %p overflowed", count)); 90332755Savg if (old == 0) 91332755Savg return (0); 92332755Savg if (atomic_fcmpset_int(count, &old, old + 1)) 93332755Savg return (1); 94332755Savg } 95332755Savg} 96332755Savg 97339862Shselaskystatic __inline __result_use_check int 98332755Savgrefcount_release_if_not_last(volatile u_int *count) 99332755Savg{ 100332755Savg u_int old; 101332755Savg 102332755Savg old = *count; 103332755Savg for (;;) { 104339862Shselasky KASSERT(old > 0, ("refcount %p is zero", count)); 105332755Savg if (old == 1) 106332755Savg return (0); 107332755Savg if (atomic_fcmpset_int(count, &old, old - 1)) 108332755Savg return (1); 109332755Savg } 110332755Savg} 111332755Savg 112150629Sjhb#endif /* ! __SYS_REFCOUNT_H__ */ 113