1 /* 2 * Copyright (c) 2018-2019 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_RWSEM_H_ 28 #define _LINUX_RWSEM_H_ 29 30 #include <linux/types.h> 31 #include <linux/kernel.h> 32 #include <linux/list.h> 33 #include <linux/spinlock.h> 34 #include <linux/atomic.h> 35 36 #define down_read(semaphore) lockmgr((semaphore), LK_SHARED) 37 #define up_read(semaphore) lockmgr((semaphore), LK_RELEASE) 38 39 #define down_write(semaphore) lockmgr((semaphore), LK_EXCLUSIVE) 40 #define up_write(semaphore) lockmgr((semaphore), LK_RELEASE) 41 42 /* 43 * trylock for reading -- returns 1 if successful, 0 if contention 44 */ 45 static inline int 46 down_read_trylock(struct lock *sem) { 47 return !lockmgr(sem, LK_EXCLUSIVE|LK_NOWAIT); 48 } 49 50 #endif /* _LINUX_RWSEM_H_ */ 51