1 /* 2 * Copyright 2010-2015 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_SPINLOCK_CAS_H 28 #define CK_SPINLOCK_CAS_H 29 30 #include <ck_backoff.h> 31 #include <ck_cc.h> 32 #include <ck_elide.h> 33 #include <ck_pr.h> 34 #include <ck_stdbool.h> 35 36 #ifndef CK_F_SPINLOCK_CAS 37 #define CK_F_SPINLOCK_CAS 38 /* 39 * This is a simple CACAS (TATAS) spinlock implementation. 40 */ 41 struct ck_spinlock_cas { 42 unsigned int value; 43 }; 44 typedef struct ck_spinlock_cas ck_spinlock_cas_t; 45 46 #define CK_SPINLOCK_CAS_INITIALIZER {false} 47 48 CK_CC_INLINE static void 49 ck_spinlock_cas_init(struct ck_spinlock_cas *lock) 50 { 51 52 lock->value = false; 53 ck_pr_barrier(); 54 return; 55 } 56 57 CK_CC_INLINE static bool 58 ck_spinlock_cas_trylock(struct ck_spinlock_cas *lock) 59 { 60 unsigned int value; 61 62 value = ck_pr_fas_uint(&lock->value, true); 63 ck_pr_fence_lock(); 64 return !value; 65 } 66 67 CK_CC_INLINE static bool 68 ck_spinlock_cas_locked(struct ck_spinlock_cas *lock) 69 { 70 bool r = ck_pr_load_uint(&lock->value); 71 72 ck_pr_fence_acquire(); 73 return r; 74 } 75 76 CK_CC_INLINE static void 77 ck_spinlock_cas_lock(struct ck_spinlock_cas *lock) 78 { 79 80 while (ck_pr_cas_uint(&lock->value, false, true) == false) { 81 while (ck_pr_load_uint(&lock->value) == true) 82 ck_pr_stall(); 83 } 84 85 ck_pr_fence_lock(); 86 return; 87 } 88 89 CK_CC_INLINE static void 90 ck_spinlock_cas_lock_eb(struct ck_spinlock_cas *lock) 91 { 92 ck_backoff_t backoff = CK_BACKOFF_INITIALIZER; 93 94 while (ck_pr_cas_uint(&lock->value, false, true) == false) 95 ck_backoff_eb(&backoff); 96 97 ck_pr_fence_lock(); 98 return; 99 } 100 101 CK_CC_INLINE static void 102 ck_spinlock_cas_unlock(struct ck_spinlock_cas *lock) 103 { 104 105 /* Set lock state to unlocked. */ 106 ck_pr_fence_unlock(); 107 ck_pr_store_uint(&lock->value, false); 108 return; 109 } 110 111 CK_ELIDE_PROTOTYPE(ck_spinlock_cas, ck_spinlock_cas_t, 112 ck_spinlock_cas_locked, ck_spinlock_cas_lock, 113 ck_spinlock_cas_locked, ck_spinlock_cas_unlock) 114 115 CK_ELIDE_TRYLOCK_PROTOTYPE(ck_spinlock_cas, ck_spinlock_cas_t, 116 ck_spinlock_cas_locked, ck_spinlock_cas_trylock) 117 118 #endif /* CK_F_SPINLOCK_CAS */ 119 #endif /* CK_SPINLOCK_CAS_H */ 120