1 /* 2 * Copyright (c) 2020 François Tigeot <ftigeot@wolfpond.org> 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice unmodified, this list of conditions, and the following 10 * disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27 #ifndef _LINUX_REFCOUNT_H_ 28 #define _LINUX_REFCOUNT_H_ 29 30 #include <linux/atomic.h> 31 #include <linux/mutex.h> 32 #include <linux/spinlock.h> 33 #include <linux/kernel.h> 34 35 typedef struct refcount_struct { 36 atomic_t refs; 37 } refcount_t; 38 39 #define REFCOUNT_SATURATED (INT_MIN / 2) 40 41 static inline void 42 refcount_set(refcount_t *r, unsigned int n) 43 { 44 atomic_set(&r->refs, n); 45 } 46 47 static inline bool 48 refcount_dec_and_test(refcount_t *r) 49 { 50 return atomic_dec_and_test(&r->refs); 51 } 52 53 static inline void 54 refcount_inc(refcount_t *r) 55 { 56 int old_value = atomic_fetchadd_int(&r->refs.counter, 1); 57 58 if (old_value <= 0) 59 refcount_set(r, REFCOUNT_SATURATED); 60 } 61 62 #endif /* _LINUX_REFCOUNT_H_ */ 63