1 /* 2 * Copyright 2009-2015 Samy Al Bahra. 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, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 */ 26 27 #ifndef CK_BACKOFF_H 28 #define CK_BACKOFF_H 29 30 #include <ck_cc.h> 31 #include <ck_pr.h> 32 33 #ifndef CK_BACKOFF_CEILING 34 #define CK_BACKOFF_CEILING ((1 << 20) - 1) 35 #endif 36 37 #define CK_BACKOFF_INITIALIZER (1 << 9) 38 39 typedef unsigned int ck_backoff_t; 40 41 /* 42 * This is a exponential back-off implementation. 43 */ 44 CK_CC_INLINE static void 45 ck_backoff_eb(unsigned int *c) 46 { 47 unsigned int i, ceiling; 48 49 ceiling = *c; 50 for (i = 0; i < ceiling; i++) 51 ck_pr_barrier(); 52 53 *c = ceiling << (ceiling < CK_BACKOFF_CEILING); 54 return; 55 } 56 57 #endif /* CK_BACKOFF_H */ 58