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 <syscall.h>
  37 #include <unistd.h>
  38 #include <stdint.h>
  39
  40 #include <urcu/compiler.h>
  41 #include <urcu/arch.h>
  42 #include <urcu/system.h>
  43 #include <urcu/uatomic.h>
  44 #include <urcu/list.h>
  45 #include <urcu/futex.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 /*
  60  * If a reader is really non-cooperative and refuses to commit its
  61  * rcu_reader.ctr count to memory (there is no barrier in the reader
  62  * per-se), kick it after a few loops waiting for it.
  63  */
  64 #define KICK_READER_LOOPS 10000
  65
  66 /*
  67  * Active attempts to check for reader Q.S. before calling futex().
  68  */
  69 #define RCU_QS_ACTIVE_ATTEMPTS 100
  70
  71 #ifdef DEBUG_RCU
  72 #define rcu_assert(args...)     assert(args)
  73 #else
  74 #define rcu_assert(args...)
  75 #endif
  76
  77 #ifdef DEBUG_YIELD
  78 #include <sched.h>
  79 #include <time.h>
  80 #include <pthread.h>
  81 #include <unistd.h>
  82
  83 #define YIELD_READ      (1 << 0)
  84 #define YIELD_WRITE     (1 << 1)
  85
  86 /* maximum sleep delay, in us */
  87 #define MAX_SLEEP 50
  88
  89 extern unsigned int yield_active;
  90 extern unsigned int __thread rand_yield;
  91
  92 static inline void debug_yield_read(void)
  93 {
  94         if (yield_active & YIELD_READ)
  95                 if (rand_r(&rand_yield) & 0x1)
  96                         usleep(rand_r(&rand_yield) % MAX_SLEEP);
  97 }
  98
  99 static inline void debug_yield_write(void)
 100 {
 101         if (yield_active & YIELD_WRITE)
 102                 if (rand_r(&rand_yield) & 0x1)
 103                         usleep(rand_r(&rand_yield) % MAX_SLEEP);
 104 }
 105
 106 static inline void debug_yield_init(void)
 107 {
 108         rand_yield = time(NULL) ^ pthread_self();
 109 }
 110 #else
 111 static inline void debug_yield_read(void)
 112 {
 113 }
 114
 115 static inline void debug_yield_write(void)
 116 {
 117 }
 118
 119 static inline void debug_yield_init(void)
 120 {
 121
 122 }
 123 #endif
 124
 125 #define RCU_GP_ONLINE           (1UL << 0)
 126 #define RCU_GP_CTR              (1UL << 1)
 127
 128 /*
 129  * Global quiescent period counter with low-order bits unused.
 130  * Using a int rather than a char to eliminate false register dependencies
 131  * causing stalls on some architectures.
 132  */
 133 extern unsigned long rcu_gp_ctr;
 134
 135 struct rcu_reader {
 136         /* Data used by both reader and synchronize_rcu() */
 137         unsigned long ctr;
 138         /* Data used for registry */
 139         struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
 140         pthread_t tid;
 141 };
 142
 143 extern struct rcu_reader __thread rcu_reader;
 144
 145 extern int32_t gp_futex;
 146
 147 /*
 148  * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
 149  */
 150 static inline void wake_up_gp(void)
 151 {
 152         if (unlikely(uatomic_read(&gp_futex) == -1)) {
 153                 uatomic_set(&gp_futex, 0);
 154                 futex_noasync(&gp_futex, FUTEX_WAKE, 1,
 155                       NULL, NULL, 0);
 156         }
 157 }
 158
 159 static inline int rcu_gp_ongoing(unsigned long *ctr)
 160 {
 161         unsigned long v;
 162
 163         v = CMM_LOAD_SHARED(*ctr);
 164         return v && (v != rcu_gp_ctr);
 165 }
 166
 167 static inline void _rcu_read_lock(void)
 168 {
 169         rcu_assert(rcu_reader.ctr);
 170 }
 171
 172 static inline void _rcu_read_unlock(void)
 173 {
 174 }
 175
 176 static inline void _rcu_quiescent_state(void)
 177 {
 178         cmm_smp_mb();
 179         _CMM_STORE_SHARED(rcu_reader.ctr, _CMM_LOAD_SHARED(rcu_gp_ctr));
 180         cmm_smp_mb();   /* write rcu_reader.ctr before read futex */
 181         wake_up_gp();
 182         cmm_smp_mb();
 183 }
 184
 185 static inline void _rcu_thread_offline(void)
 186 {
 187         cmm_smp_mb();
 188         CMM_STORE_SHARED(rcu_reader.ctr, 0);
 189         cmm_smp_mb();   /* write rcu_reader.ctr before read futex */
 190         wake_up_gp();
 191         cmm_barrier();  /* Ensure the compiler does not reorder us with mutex */
 192 }
 193
 194 static inline void _rcu_thread_online(void)
 195 {
 196         cmm_barrier();  /* Ensure the compiler does not reorder us with mutex */
 197         _CMM_STORE_SHARED(rcu_reader.ctr, CMM_LOAD_SHARED(rcu_gp_ctr));
 198         cmm_smp_mb();
 199 }
 200
 201 #ifdef __cplusplus
 202 }
 203 #endif
 204
 205 #endif /* _URCU_QSBR_STATIC_H */