1309260Scognet/* 2309260Scognet * Copyright 2014 Samy Al Bahra. 3309260Scognet * All rights reserved. 4309260Scognet * 5309260Scognet * Redistribution and use in source and binary forms, with or without 6309260Scognet * modification, are permitted provided that the following conditions 7309260Scognet * are met: 8309260Scognet * 1. Redistributions of source code must retain the above copyright 9309260Scognet * notice, this list of conditions and the following disclaimer. 10309260Scognet * 2. Redistributions in binary form must reproduce the above copyright 11309260Scognet * notice, this list of conditions and the following disclaimer in the 12309260Scognet * documentation and/or other materials provided with the distribution. 13309260Scognet * 14309260Scognet * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15309260Scognet * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16309260Scognet * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17309260Scognet * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18309260Scognet * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19309260Scognet * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20309260Scognet * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21309260Scognet * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22309260Scognet * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23309260Scognet * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24309260Scognet * SUCH DAMAGE. 25309260Scognet */ 26309260Scognet 27309260Scognet#ifndef CK_TFLOCK_TICKET_H 28309260Scognet#define CK_TFLOCK_TICKET_H 29309260Scognet 30309260Scognet/* 31309260Scognet * This is an implementation of task-fair locks derived from the work 32309260Scognet * described in: 33309260Scognet * John M. Mellor-Crummey and Michael L. Scott. 1991. 34309260Scognet * Scalable reader-writer synchronization for shared-memory 35309260Scognet * multiprocessors. SIGPLAN Not. 26, 7 (April 1991), 106-113. 36309260Scognet */ 37309260Scognet 38309260Scognet#include <ck_cc.h> 39309260Scognet#include <ck_pr.h> 40309260Scognet 41309260Scognetstruct ck_tflock_ticket { 42309260Scognet uint32_t request; 43309260Scognet uint32_t completion; 44309260Scognet}; 45309260Scognettypedef struct ck_tflock_ticket ck_tflock_ticket_t; 46309260Scognet 47309260Scognet#define CK_TFLOCK_TICKET_INITIALIZER { 0, 0 } 48309260Scognet 49309260Scognet#define CK_TFLOCK_TICKET_RC_INCR 0x10000U /* Read-side increment. */ 50309260Scognet#define CK_TFLOCK_TICKET_WC_INCR 0x1U /* Write-side increment. */ 51309260Scognet#define CK_TFLOCK_TICKET_W_MASK 0xffffU /* Write-side mask. */ 52309260Scognet#define CK_TFLOCK_TICKET_WC_TOPMSK 0x8000U /* Write clear mask for overflow. */ 53309260Scognet#define CK_TFLOCK_TICKET_RC_TOPMSK 0x80000000U /* Read clear mask for overflow. */ 54309260Scognet 55309260ScognetCK_CC_INLINE static uint32_t 56309260Scognetck_tflock_ticket_fca_32(uint32_t *target, uint32_t mask, uint32_t delta) 57309260Scognet{ 58309260Scognet uint32_t snapshot = ck_pr_load_32(target); 59309260Scognet uint32_t goal; 60309260Scognet 61309260Scognet for (;;) { 62309260Scognet goal = (snapshot & ~mask) + delta; 63309260Scognet if (ck_pr_cas_32_value(target, snapshot, goal, &snapshot) == true) 64309260Scognet break; 65309260Scognet 66309260Scognet ck_pr_stall(); 67309260Scognet } 68309260Scognet 69309260Scognet return snapshot; 70309260Scognet} 71309260Scognet 72309260ScognetCK_CC_INLINE static void 73309260Scognetck_tflock_ticket_init(struct ck_tflock_ticket *pf) 74309260Scognet{ 75309260Scognet 76309260Scognet pf->request = pf->completion = 0; 77309260Scognet ck_pr_barrier(); 78309260Scognet return; 79309260Scognet} 80309260Scognet 81309260ScognetCK_CC_INLINE static void 82309260Scognetck_tflock_ticket_write_lock(struct ck_tflock_ticket *lock) 83309260Scognet{ 84309260Scognet uint32_t previous; 85309260Scognet 86309260Scognet previous = ck_tflock_ticket_fca_32(&lock->request, CK_TFLOCK_TICKET_WC_TOPMSK, 87309260Scognet CK_TFLOCK_TICKET_WC_INCR); 88309260Scognet ck_pr_fence_atomic_load(); 89309260Scognet while (ck_pr_load_32(&lock->completion) != previous) 90309260Scognet ck_pr_stall(); 91309260Scognet 92309260Scognet ck_pr_fence_lock(); 93309260Scognet return; 94309260Scognet} 95309260Scognet 96309260ScognetCK_CC_INLINE static void 97309260Scognetck_tflock_ticket_write_unlock(struct ck_tflock_ticket *lock) 98309260Scognet{ 99309260Scognet 100309260Scognet ck_pr_fence_unlock(); 101309260Scognet ck_tflock_ticket_fca_32(&lock->completion, CK_TFLOCK_TICKET_WC_TOPMSK, 102309260Scognet CK_TFLOCK_TICKET_WC_INCR); 103309260Scognet return; 104309260Scognet} 105309260Scognet 106309260ScognetCK_CC_INLINE static void 107309260Scognetck_tflock_ticket_read_lock(struct ck_tflock_ticket *lock) 108309260Scognet{ 109309260Scognet uint32_t previous; 110309260Scognet 111309260Scognet previous = ck_tflock_ticket_fca_32(&lock->request, 112309260Scognet CK_TFLOCK_TICKET_RC_TOPMSK, CK_TFLOCK_TICKET_RC_INCR) & 113309260Scognet CK_TFLOCK_TICKET_W_MASK; 114309260Scognet 115309260Scognet ck_pr_fence_atomic_load(); 116309260Scognet 117309260Scognet while ((ck_pr_load_32(&lock->completion) & 118309260Scognet CK_TFLOCK_TICKET_W_MASK) != previous) { 119309260Scognet ck_pr_stall(); 120309260Scognet } 121309260Scognet 122309260Scognet ck_pr_fence_lock(); 123309260Scognet return; 124309260Scognet} 125309260Scognet 126309260ScognetCK_CC_INLINE static void 127309260Scognetck_tflock_ticket_read_unlock(struct ck_tflock_ticket *lock) 128309260Scognet{ 129309260Scognet 130309260Scognet ck_pr_fence_unlock(); 131309260Scognet ck_tflock_ticket_fca_32(&lock->completion, CK_TFLOCK_TICKET_RC_TOPMSK, 132309260Scognet CK_TFLOCK_TICKET_RC_INCR); 133309260Scognet return; 134309260Scognet} 135309260Scognet 136309260Scognet#endif /* CK_TFLOCK_TICKET_H */ 137