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 /*
  59  * If a reader is really non-cooperative and refuses to commit its
  60  * rcu_reader.ctr count to memory (there is no barrier in the reader
  61  * per-se), kick it after a few loops waiting for it.
  62  */
  63 #define KICK_READER_LOOPS 10000
  64
  65 /*
  66  * Active attempts to check for reader Q.S. before calling futex().
  67  */
  68 #define RCU_QS_ACTIVE_ATTEMPTS 100
  69
  70 #ifdef DEBUG_RCU
  71 #define rcu_assert(args...)     assert(args)
  72 #else
  73 #define rcu_assert(args...)
  74 #endif
  75
  76 #ifdef DEBUG_YIELD
  77 #include <sched.h>
  78 #include <time.h>
  79 #include <pthread.h>
  80 #include <unistd.h>
  81
  82 #define YIELD_READ      (1 << 0)
  83 #define YIELD_WRITE     (1 << 1)
  84
  85 /* maximum sleep delay, in us */
  86 #define MAX_SLEEP 50
  87
  88 extern unsigned int yield_active;
  89 extern unsigned int __thread rand_yield;
  90
  91 static inline void debug_yield_read(void)
  92 {
  93         if (yield_active & YIELD_READ)
  94                 if (rand_r(&rand_yield) & 0x1)
  95                         usleep(rand_r(&rand_yield) % MAX_SLEEP);
  96 }
  97
  98 static inline void debug_yield_write(void)
  99 {
 100         if (yield_active & YIELD_WRITE)
 101                 if (rand_r(&rand_yield) & 0x1)
 102                         usleep(rand_r(&rand_yield) % MAX_SLEEP);
 103 }
 104
 105 static inline void debug_yield_init(void)
 106 {
 107         rand_yield = time(NULL) ^ pthread_self();
 108 }
 109 #else
 110 static inline void debug_yield_read(void)
 111 {
 112 }
 113
 114 static inline void debug_yield_write(void)
 115 {
 116 }
 117
 118 static inline void debug_yield_init(void)
 119 {
 120
 121 }
 122 #endif
 123
 124 #define RCU_GP_ONLINE           (1UL << 0)
 125 #define RCU_GP_CTR              (1UL << 1)
 126
 127 /*
 128  * Global quiescent period counter with low-order bits unused.
 129  * Using a int rather than a char to eliminate false register dependencies
 130  * causing stalls on some architectures.
 131  */
 132 extern unsigned long rcu_gp_ctr;
 133
 134 struct rcu_reader {
 135         /* Data used by both reader and synchronize_rcu() */
 136         unsigned long ctr;
 137         /* Data used for registry */
 138         struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
 139         pthread_t tid;
 140 };
 141
 142 extern struct rcu_reader __thread rcu_reader;
 143
 144 extern int32_t gp_futex;
 145
 146 /*
 147  * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
 148  */
 149 static inline void wake_up_gp(void)
 150 {
 151         if (unlikely(uatomic_read(&gp_futex) == -1)) {
 152                 uatomic_set(&gp_futex, 0);
 153                 futex_noasync(&gp_futex, FUTEX_WAKE, 1,
 154                       NULL, NULL, 0);
 155         }
 156 }
 157
 158 static inline int rcu_gp_ongoing(unsigned long *ctr)
 159 {
 160         unsigned long v;
 161
 162         v = CMM_LOAD_SHARED(*ctr);
 163         return v && (v != rcu_gp_ctr);
 164 }
 165
 166 static inline void _rcu_read_lock(void)
 167 {
 168         rcu_assert(rcu_reader.ctr);
 169 }
 170
 171 static inline void _rcu_read_unlock(void)
 172 {
 173 }
 174
 175 static inline void _rcu_quiescent_state(void)
 176 {
 177         cmm_smp_mb();
 178         _CMM_STORE_SHARED(rcu_reader.ctr, _CMM_LOAD_SHARED(rcu_gp_ctr));
 179         cmm_smp_mb();   /* write rcu_reader.ctr before read futex */
 180         wake_up_gp();
 181         cmm_smp_mb();
 182 }
 183
 184 static inline void _rcu_thread_offline(void)
 185 {
 186         cmm_smp_mb();
 187         CMM_STORE_SHARED(rcu_reader.ctr, 0);
 188         cmm_smp_mb();   /* write rcu_reader.ctr before read futex */
 189         wake_up_gp();
 190         cmm_barrier();  /* Ensure the compiler does not reorder us with mutex */
 191 }
 192
 193 static inline void _rcu_thread_online(void)
 194 {
 195         cmm_barrier();  /* Ensure the compiler does not reorder us with mutex */
 196         _CMM_STORE_SHARED(rcu_reader.ctr, CMM_LOAD_SHARED(rcu_gp_ctr));
 197         cmm_smp_mb();
 198 }
 199
 200 #ifdef __cplusplus
 201 }
 202 #endif
 203
 204 #endif /* _URCU_QSBR_STATIC_H */