urcu/static/urcu-qsbr.h

   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
  46 #ifdef __cplusplus
  47 extern "C" {
  48 #endif
  49
  50 /*
  51  * This code section can only be included in LGPL 2.1 compatible source code.
  52  * See below for the function call wrappers which can be used in code meant to
  53  * be only linked with the Userspace RCU library. This comes with a small
  54  * performance degradation on the read-side due to the added function calls.
  55  * This is required to permit relinking with newer versions of the library.
  56  */
  57
  58 #ifdef DEBUG_RCU
  59 #define rcu_assert(args...)     assert(args)
  60 #else
  61 #define rcu_assert(args...)
  62 #endif
  63
  64 #ifdef DEBUG_YIELD
  65 #include <sched.h>
  66 #include <time.h>
  67 #include <pthread.h>
  68 #include <unistd.h>
  69
  70 #define YIELD_READ      (1 << 0)
  71 #define YIELD_WRITE     (1 << 1)
  72
  73 /* maximum sleep delay, in us */
  74 #define MAX_SLEEP 50
  75
  76 extern unsigned int yield_active;
  77 extern unsigned int __thread rand_yield;
  78
  79 static inline void debug_yield_read(void)
  80 {
  81         if (yield_active & YIELD_READ)
  82                 if (rand_r(&rand_yield) & 0x1)
  83                         usleep(rand_r(&rand_yield) % MAX_SLEEP);
  84 }
  85
  86 static inline void debug_yield_write(void)
  87 {
  88         if (yield_active & YIELD_WRITE)
  89                 if (rand_r(&rand_yield) & 0x1)
  90                         usleep(rand_r(&rand_yield) % MAX_SLEEP);
  91 }
  92
  93 static inline void debug_yield_init(void)
  94 {
  95         rand_yield = time(NULL) ^ pthread_self();
  96 }
  97 #else
  98 static inline void debug_yield_read(void)
  99 {
 100 }
 101
 102 static inline void debug_yield_write(void)
 103 {
 104 }
 105
 106 static inline void debug_yield_init(void)
 107 {
 108
 109 }
 110 #endif
 111
 112 #define RCU_GP_ONLINE           (1UL << 0)
 113 #define RCU_GP_CTR              (1UL << 1)
 114
 115 /*
 116  * Global quiescent period counter with low-order bits unused.
 117  * Using a int rather than a char to eliminate false register dependencies
 118  * causing stalls on some architectures.
 119  */
 120 extern unsigned long rcu_gp_ctr;
 121
 122 struct rcu_reader {
 123         /* Data used by both reader and synchronize_rcu() */
 124         unsigned long ctr;
 125         /* Data used for registry */
 126         struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
 127         int waiting;
 128         pthread_t tid;
 129 };
 130
 131 extern struct rcu_reader __thread rcu_reader;
 132
 133 extern int32_t gp_futex;
 134
 135 /*
 136  * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
 137  */
 138 static inline void wake_up_gp(void)
 139 {
 140         if (caa_unlikely(_CMM_LOAD_SHARED(rcu_reader.waiting))) {
 141                 _CMM_STORE_SHARED(rcu_reader.waiting, 0);
 142                 cmm_smp_mb();
 143                 if (uatomic_read(&gp_futex) != -1)
 144                         return;
 145                 uatomic_set(&gp_futex, 0);
 146                 futex_noasync(&gp_futex, FUTEX_WAKE, 1,
 147                       NULL, NULL, 0);
 148         }
 149 }
 150
 151 static inline int rcu_gp_ongoing(unsigned long *ctr)
 152 {
 153         unsigned long v;
 154
 155         v = CMM_LOAD_SHARED(*ctr);
 156         return v && (v != rcu_gp_ctr);
 157 }
 158
 159 static inline void _rcu_read_lock(void)
 160 {
 161         rcu_assert(rcu_reader.ctr);
 162 }
 163
 164 static inline void _rcu_read_unlock(void)
 165 {
 166 }
 167
 168 static inline void _rcu_quiescent_state(void)
 169 {
 170         cmm_smp_mb();
 171         _CMM_STORE_SHARED(rcu_reader.ctr, _CMM_LOAD_SHARED(rcu_gp_ctr));
 172         cmm_smp_mb();   /* write rcu_reader.ctr before read futex */
 173         wake_up_gp();
 174         cmm_smp_mb();
 175 }
 176
 177 static inline void _rcu_thread_offline(void)
 178 {
 179         cmm_smp_mb();
 180         CMM_STORE_SHARED(rcu_reader.ctr, 0);
 181         cmm_smp_mb();   /* write rcu_reader.ctr before read futex */
 182         wake_up_gp();
 183         cmm_barrier();  /* Ensure the compiler does not reorder us with mutex */
 184 }
 185
 186 static inline void _rcu_thread_online(void)
 187 {
 188         cmm_barrier();  /* Ensure the compiler does not reorder us with mutex */
 189         _CMM_STORE_SHARED(rcu_reader.ctr, CMM_LOAD_SHARED(rcu_gp_ctr));
 190         cmm_smp_mb();
 191 }
 192
 193 #ifdef __cplusplus
 194 }
 195 #endif
 196
 197 #endif /* _URCU_QSBR_STATIC_H */