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 CODE THAT IS TO BE RECOMPILED ON EACH LIBURCU
  10  * RELEASE. See urcu.h for linking dynamically with the userspace rcu 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) ^ (unsigned long) 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                 /*
 148                  * Ignoring return value until we can make this function
 149                  * return something (because urcu_die() is not publicly
 150                  * exposed).
 151                  */
 152                 (void) futex_noasync(&gp_futex, FUTEX_WAKE, 1,
 153                                 NULL, NULL, 0);
 154         }
 155 }
 156
 157 static inline int rcu_gp_ongoing(unsigned long *ctr)
 158 {
 159         unsigned long v;
 160
 161         v = CMM_LOAD_SHARED(*ctr);
 162         return v && (v != rcu_gp_ctr);
 163 }
 164
 165 /*
 166  * Enter an RCU read-side critical section.
 167  *
 168  * This function is less than 10 lines long.  The intent is that this
 169  * function meets the 10-line criterion for LGPL, allowing this function
 170  * to be invoked directly from non-LGPL code.
 171  */
 172 static inline void _rcu_read_lock(void)
 173 {
 174         rcu_assert(URCU_TLS(rcu_reader).ctr);
 175 }
 176
 177 /*
 178  * Exit an RCU read-side critical section.
 179  *
 180  * This function is less than 10 lines long.  The intent is that this
 181  * function meets the 10-line criterion for LGPL, allowing this function
 182  * to be invoked directly from non-LGPL code.
 183  */
 184 static inline void _rcu_read_unlock(void)
 185 {
 186 }
 187
 188 /*
 189  * Inform RCU of a quiescent state.
 190  *
 191  * This function is less than 10 lines long.  The intent is that this
 192  * function meets the 10-line criterion for LGPL, allowing this function
 193  * to be invoked directly from non-LGPL code.
 194  */
 195 static inline void _rcu_quiescent_state(void)
 196 {
 197         cmm_smp_mb();
 198         _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, _CMM_LOAD_SHARED(rcu_gp_ctr));
 199         cmm_smp_mb();   /* write URCU_TLS(rcu_reader).ctr before read futex */
 200         wake_up_gp();
 201         cmm_smp_mb();
 202 }
 203
 204 /*
 205  * Take a thread offline, prohibiting it from entering further RCU
 206  * read-side critical sections.
 207  *
 208  * This function is less than 10 lines long.  The intent is that this
 209  * function meets the 10-line criterion for LGPL, allowing this function
 210  * to be invoked directly from non-LGPL code.
 211  */
 212 static inline void _rcu_thread_offline(void)
 213 {
 214         cmm_smp_mb();
 215         CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, 0);
 216         cmm_smp_mb();   /* write URCU_TLS(rcu_reader).ctr before read futex */
 217         wake_up_gp();
 218         cmm_barrier();  /* Ensure the compiler does not reorder us with mutex */
 219 }
 220
 221 /*
 222  * Bring a thread online, allowing it to once again enter RCU
 223  * read-side critical sections.
 224  *
 225  * This function is less than 10 lines long.  The intent is that this
 226  * function meets the 10-line criterion for LGPL, allowing this function
 227  * to be invoked directly from non-LGPL code.
 228  */
 229 static inline void _rcu_thread_online(void)
 230 {
 231         cmm_barrier();  /* Ensure the compiler does not reorder us with mutex */
 232         _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, CMM_LOAD_SHARED(rcu_gp_ctr));
 233         cmm_smp_mb();
 234 }
 235
 236 #ifdef __cplusplus
 237 }
 238 #endif
 239
 240 #endif /* _URCU_QSBR_STATIC_H */