1/* 2 * Copyright 2014 Jaidev Sridhar. 3 * Copyright 2014 Samy Al Bahra. 4 * All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following 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 AND CONTRIBUTORS ``AS IS'' AND 16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25 * SUCH DAMAGE. 26 */ 27 28#ifndef CK_SWLOCK_H 29#define CK_SWLOCK_H 30 31#include <ck_elide.h> 32#include <ck_limits.h> 33#include <ck_pr.h> 34#include <ck_stdbool.h> 35#include <ck_stddef.h> 36 37struct ck_swlock { 38 uint32_t value; 39}; 40typedef struct ck_swlock ck_swlock_t; 41 42#define CK_SWLOCK_INITIALIZER {0} 43#define CK_SWLOCK_WRITER_BIT (1UL << 31) 44#define CK_SWLOCK_LATCH_BIT (1UL << 30) 45#define CK_SWLOCK_WRITER_MASK (CK_SWLOCK_LATCH_BIT | CK_SWLOCK_WRITER_BIT) 46#define CK_SWLOCK_READER_MASK (UINT32_MAX ^ CK_SWLOCK_WRITER_MASK) 47 48CK_CC_INLINE static void 49ck_swlock_init(struct ck_swlock *rw) 50{ 51 52 rw->value = 0; 53 ck_pr_barrier(); 54 return; 55} 56 57CK_CC_INLINE static void 58ck_swlock_write_unlock(ck_swlock_t *rw) 59{ 60 61 ck_pr_fence_unlock(); 62 ck_pr_and_32(&rw->value, CK_SWLOCK_READER_MASK); 63 return; 64} 65 66CK_CC_INLINE static bool 67ck_swlock_locked_writer(ck_swlock_t *rw) 68{ 69 bool r; 70 71 r = ck_pr_load_32(&rw->value) & CK_SWLOCK_WRITER_BIT; 72 ck_pr_fence_acquire(); 73 return r; 74} 75 76CK_CC_INLINE static void 77ck_swlock_write_downgrade(ck_swlock_t *rw) 78{ 79 80 ck_pr_inc_32(&rw->value); 81 ck_swlock_write_unlock(rw); 82 return; 83} 84 85CK_CC_INLINE static bool 86ck_swlock_locked(ck_swlock_t *rw) 87{ 88 bool r; 89 90 r = ck_pr_load_32(&rw->value); 91 ck_pr_fence_acquire(); 92 return r; 93} 94 95CK_CC_INLINE static bool 96ck_swlock_write_trylock(ck_swlock_t *rw) 97{ 98 bool r; 99 100 r = ck_pr_cas_32(&rw->value, 0, CK_SWLOCK_WRITER_BIT); 101 ck_pr_fence_lock(); 102 return r; 103} 104 105CK_ELIDE_TRYLOCK_PROTOTYPE(ck_swlock_write, ck_swlock_t, 106 ck_swlock_locked, ck_swlock_write_trylock) 107 108CK_CC_INLINE static void 109ck_swlock_write_lock(ck_swlock_t *rw) 110{ 111 112 ck_pr_or_32(&rw->value, CK_SWLOCK_WRITER_BIT); 113 while (ck_pr_load_32(&rw->value) & CK_SWLOCK_READER_MASK) 114 ck_pr_stall(); 115 116 ck_pr_fence_lock(); 117 return; 118} 119 120CK_CC_INLINE static void 121ck_swlock_write_latch(ck_swlock_t *rw) 122{ 123 124 /* Publish intent to acquire lock. */ 125 ck_pr_or_32(&rw->value, CK_SWLOCK_WRITER_BIT); 126 127 /* Stall until readers have seen the writer and cleared. */ 128 while (ck_pr_cas_32(&rw->value, CK_SWLOCK_WRITER_BIT, 129 CK_SWLOCK_WRITER_MASK) == false) { 130 do { 131 ck_pr_stall(); 132 } while (ck_pr_load_32(&rw->value) != CK_SWLOCK_WRITER_BIT); 133 } 134 135 ck_pr_fence_lock(); 136 return; 137} 138 139CK_CC_INLINE static void 140ck_swlock_write_unlatch(ck_swlock_t *rw) 141{ 142 143 ck_pr_fence_unlock(); 144 ck_pr_store_32(&rw->value, 0); 145 return; 146} 147 148CK_ELIDE_PROTOTYPE(ck_swlock_write, ck_swlock_t, 149 ck_swlock_locked, ck_swlock_write_lock, 150 ck_swlock_locked_writer, ck_swlock_write_unlock) 151 152CK_ELIDE_TRYLOCK_PROTOTYPE(ck_swlock_read, ck_swlock_t, 153 ck_swlock_locked_writer, ck_swlock_read_trylock) 154 155CK_CC_INLINE static bool 156ck_swlock_read_trylock(ck_swlock_t *rw) 157{ 158 uint32_t l = ck_pr_load_32(&rw->value); 159 160 if (l & CK_SWLOCK_WRITER_BIT) 161 return false; 162 163 l = ck_pr_faa_32(&rw->value, 1) & CK_SWLOCK_WRITER_MASK; 164 if (l == CK_SWLOCK_WRITER_BIT) 165 ck_pr_dec_32(&rw->value); 166 167 ck_pr_fence_lock(); 168 return l == 0; 169} 170 171CK_CC_INLINE static void 172ck_swlock_read_lock(ck_swlock_t *rw) 173{ 174 uint32_t l; 175 176 for (;;) { 177 while (ck_pr_load_32(&rw->value) & CK_SWLOCK_WRITER_BIT) 178 ck_pr_stall(); 179 180 l = ck_pr_faa_32(&rw->value, 1) & CK_SWLOCK_WRITER_MASK; 181 if (l == 0) 182 break; 183 184 /* 185 * If the latch bit has not been set, then the writer would 186 * have observed the reader and will wait to completion of 187 * read-side critical section. 188 */ 189 if (l == CK_SWLOCK_WRITER_BIT) 190 ck_pr_dec_32(&rw->value); 191 } 192 193 ck_pr_fence_lock(); 194 return; 195} 196 197CK_CC_INLINE static bool 198ck_swlock_locked_reader(ck_swlock_t *rw) 199{ 200 201 ck_pr_fence_load(); 202 return ck_pr_load_32(&rw->value) & CK_SWLOCK_READER_MASK; 203} 204 205CK_CC_INLINE static void 206ck_swlock_read_unlock(ck_swlock_t *rw) 207{ 208 209 ck_pr_fence_unlock(); 210 ck_pr_dec_32(&rw->value); 211 return; 212} 213 214CK_ELIDE_PROTOTYPE(ck_swlock_read, ck_swlock_t, 215 ck_swlock_locked_writer, ck_swlock_read_lock, 216 ck_swlock_locked_reader, ck_swlock_read_unlock) 217 218#endif /* CK_SWLOCK_H */ 219