| 1 | #ifndef _URCU_QSBR_STATIC_H |
| 2 | #define _URCU_QSBR_STATIC_H |
| 3 | |
| 4 | /* |
| 5 | * urcu-qsbr-static.h |
| 6 | * |
| 7 | * Userspace RCU QSBR header. |
| 8 | * |
| 9 | * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu-qsbr.h for linking |
| 10 | * dynamically with the userspace rcu QSBR library. |
| 11 | * |
| 12 | * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 13 | * Copyright (c) 2009 Paul E. McKenney, IBM Corporation. |
| 14 | * |
| 15 | * This library is free software; you can redistribute it and/or |
| 16 | * modify it under the terms of the GNU Lesser General Public |
| 17 | * License as published by the Free Software Foundation; either |
| 18 | * version 2.1 of the License, or (at your option) any later version. |
| 19 | * |
| 20 | * This library is distributed in the hope that it will be useful, |
| 21 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 22 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 23 | * Lesser General Public License for more details. |
| 24 | * |
| 25 | * You should have received a copy of the GNU Lesser General Public |
| 26 | * License along with this library; if not, write to the Free Software |
| 27 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| 28 | * |
| 29 | * IBM's contributions to this file may be relicensed under LGPLv2 or later. |
| 30 | */ |
| 31 | |
| 32 | #include <stdlib.h> |
| 33 | #include <pthread.h> |
| 34 | #include <assert.h> |
| 35 | #include <limits.h> |
| 36 | #include <unistd.h> |
| 37 | #include <stdint.h> |
| 38 | |
| 39 | #include <urcu/compiler.h> |
| 40 | #include <urcu/arch.h> |
| 41 | #include <urcu/system.h> |
| 42 | #include <urcu/uatomic.h> |
| 43 | #include <urcu/list.h> |
| 44 | #include <urcu/futex.h> |
| 45 | #include <urcu/tls-compat.h> |
| 46 | |
| 47 | #ifdef __cplusplus |
| 48 | extern "C" { |
| 49 | #endif |
| 50 | |
| 51 | /* |
| 52 | * This code section can only be included in LGPL 2.1 compatible source code. |
| 53 | * See below for the function call wrappers which can be used in code meant to |
| 54 | * be only linked with the Userspace RCU library. This comes with a small |
| 55 | * performance degradation on the read-side due to the added function calls. |
| 56 | * This is required to permit relinking with newer versions of the library. |
| 57 | */ |
| 58 | |
| 59 | #ifdef DEBUG_RCU |
| 60 | #define rcu_assert(args...) assert(args) |
| 61 | #else |
| 62 | #define rcu_assert(args...) |
| 63 | #endif |
| 64 | |
| 65 | #ifdef DEBUG_YIELD |
| 66 | #include <sched.h> |
| 67 | #include <time.h> |
| 68 | #include <pthread.h> |
| 69 | #include <unistd.h> |
| 70 | |
| 71 | #define YIELD_READ (1 << 0) |
| 72 | #define YIELD_WRITE (1 << 1) |
| 73 | |
| 74 | /* maximum sleep delay, in us */ |
| 75 | #define MAX_SLEEP 50 |
| 76 | |
| 77 | extern unsigned int yield_active; |
| 78 | extern DECLARE_URCU_TLS(unsigned int, rand_yield); |
| 79 | |
| 80 | static inline void debug_yield_read(void) |
| 81 | { |
| 82 | if (yield_active & YIELD_READ) |
| 83 | if (rand_r(&URCU_TLS(rand_yield)) & 0x1) |
| 84 | usleep(rand_r(&URCU_TLS(rand_yield)) % MAX_SLEEP); |
| 85 | } |
| 86 | |
| 87 | static inline void debug_yield_write(void) |
| 88 | { |
| 89 | if (yield_active & YIELD_WRITE) |
| 90 | if (rand_r(&URCU_TLS(rand_yield)) & 0x1) |
| 91 | usleep(rand_r(&URCU_TLS(rand_yield)) % MAX_SLEEP); |
| 92 | } |
| 93 | |
| 94 | static inline void debug_yield_init(void) |
| 95 | { |
| 96 | URCU_TLS(rand_yield) = time(NULL) ^ pthread_self(); |
| 97 | } |
| 98 | #else |
| 99 | static inline void debug_yield_read(void) |
| 100 | { |
| 101 | } |
| 102 | |
| 103 | static inline void debug_yield_write(void) |
| 104 | { |
| 105 | } |
| 106 | |
| 107 | static inline void debug_yield_init(void) |
| 108 | { |
| 109 | |
| 110 | } |
| 111 | #endif |
| 112 | |
| 113 | #define RCU_GP_ONLINE (1UL << 0) |
| 114 | #define RCU_GP_CTR (1UL << 1) |
| 115 | |
| 116 | /* |
| 117 | * Global quiescent period counter with low-order bits unused. |
| 118 | * Using a int rather than a char to eliminate false register dependencies |
| 119 | * causing stalls on some architectures. |
| 120 | */ |
| 121 | extern unsigned long rcu_gp_ctr; |
| 122 | |
| 123 | struct rcu_reader { |
| 124 | /* Data used by both reader and synchronize_rcu() */ |
| 125 | unsigned long ctr; |
| 126 | /* Data used for registry */ |
| 127 | struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE))); |
| 128 | int waiting; |
| 129 | pthread_t tid; |
| 130 | }; |
| 131 | |
| 132 | extern DECLARE_URCU_TLS(struct rcu_reader, rcu_reader); |
| 133 | |
| 134 | extern int32_t gp_futex; |
| 135 | |
| 136 | /* |
| 137 | * Wake-up waiting synchronize_rcu(). Called from many concurrent threads. |
| 138 | */ |
| 139 | static inline void wake_up_gp(void) |
| 140 | { |
| 141 | if (caa_unlikely(_CMM_LOAD_SHARED(URCU_TLS(rcu_reader).waiting))) { |
| 142 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).waiting, 0); |
| 143 | cmm_smp_mb(); |
| 144 | if (uatomic_read(&gp_futex) != -1) |
| 145 | return; |
| 146 | uatomic_set(&gp_futex, 0); |
| 147 | futex_noasync(&gp_futex, FUTEX_WAKE, 1, |
| 148 | NULL, NULL, 0); |
| 149 | } |
| 150 | } |
| 151 | |
| 152 | static inline int rcu_gp_ongoing(unsigned long *ctr) |
| 153 | { |
| 154 | unsigned long v; |
| 155 | |
| 156 | v = CMM_LOAD_SHARED(*ctr); |
| 157 | return v && (v != rcu_gp_ctr); |
| 158 | } |
| 159 | |
| 160 | static inline void _rcu_read_lock(void) |
| 161 | { |
| 162 | rcu_assert(URCU_TLS(rcu_reader).ctr); |
| 163 | } |
| 164 | |
| 165 | static inline void _rcu_read_unlock(void) |
| 166 | { |
| 167 | } |
| 168 | |
| 169 | static inline void _rcu_quiescent_state(void) |
| 170 | { |
| 171 | cmm_smp_mb(); |
| 172 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, _CMM_LOAD_SHARED(rcu_gp_ctr)); |
| 173 | cmm_smp_mb(); /* write URCU_TLS(rcu_reader).ctr before read futex */ |
| 174 | wake_up_gp(); |
| 175 | cmm_smp_mb(); |
| 176 | } |
| 177 | |
| 178 | static inline void _rcu_thread_offline(void) |
| 179 | { |
| 180 | cmm_smp_mb(); |
| 181 | CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, 0); |
| 182 | cmm_smp_mb(); /* write URCU_TLS(rcu_reader).ctr before read futex */ |
| 183 | wake_up_gp(); |
| 184 | cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */ |
| 185 | } |
| 186 | |
| 187 | static inline void _rcu_thread_online(void) |
| 188 | { |
| 189 | cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */ |
| 190 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, CMM_LOAD_SHARED(rcu_gp_ctr)); |
| 191 | cmm_smp_mb(); |
| 192 | } |
| 193 | |
| 194 | #ifdef __cplusplus |
| 195 | } |
| 196 | #endif |
| 197 | |
| 198 | #endif /* _URCU_QSBR_STATIC_H */ |