include/urcu/static/urcu-memb.h

   1 #ifndef _URCU_MEMB_STATIC_H
   2 #define _URCU_MEMB_STATIC_H
   3
   4 /*
   5  * urcu-memb-static.h
   6  *
   7  * Userspace RCU 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 <unistd.h>
  35 #include <stdint.h>
  36
  37 #include <urcu/debug.h>
  38 #include <urcu/config.h>
  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 #include <urcu/static/urcu-common.h>
  47
  48 #ifdef __cplusplus
  49 extern "C" {
  50 #endif
  51
  52 /*
  53  * This code section can only be included in LGPL 2.1 compatible source code.
  54  * See below for the function call wrappers which can be used in code meant to
  55  * be only linked with the Userspace RCU library. This comes with a small
  56  * performance degradation on the read-side due to the added function calls.
  57  * This is required to permit relinking with newer versions of the library.
  58  */
  59
  60 /*
  61  * Slave barriers are only guaranteed to be ordered wrt master barriers.
  62  *
  63  * The pair ordering is detailed as (O: ordered, X: not ordered) :
  64  *               slave  master
  65  *        slave    X      O
  66  *        master   O      O
  67  */
  68
  69 #ifdef CONFIG_RCU_FORCE_SYS_MEMBARRIER
  70 #define urcu_memb_has_sys_membarrier            1
  71 #else
  72 extern int urcu_memb_has_sys_membarrier;
  73 #endif
  74
  75 static inline void urcu_memb_smp_mb_slave(void)
  76 {
  77         if (caa_likely(urcu_memb_has_sys_membarrier))
  78                 cmm_barrier();
  79         else
  80                 cmm_smp_mb();
  81 }
  82
  83 extern struct urcu_gp urcu_memb_gp;
  84
  85 extern DECLARE_URCU_TLS(struct urcu_reader, urcu_memb_reader);
  86
  87 /*
  88  * Helper for _rcu_read_lock().  The format of urcu_memb_gp.ctr (as well as
  89  * the per-thread rcu_reader.ctr) has the lower-order bits containing a count of
  90  * _rcu_read_lock() nesting, and a single high-order URCU_BP_GP_CTR_PHASE bit
  91  * that contains either zero or one.  The smp_mb_slave() ensures that the accesses in
  92  * _rcu_read_lock() happen before the subsequent read-side critical section.
  93  */
  94 static inline void _urcu_memb_read_lock_update(unsigned long tmp)
  95 {
  96         if (caa_likely(!(tmp & URCU_GP_CTR_NEST_MASK))) {
  97                 _CMM_STORE_SHARED(URCU_TLS(urcu_memb_reader).ctr, _CMM_LOAD_SHARED(urcu_memb_gp.ctr));
  98                 urcu_memb_smp_mb_slave();
  99         } else
 100                 _CMM_STORE_SHARED(URCU_TLS(urcu_memb_reader).ctr, tmp + URCU_GP_COUNT);
 101 }
 102
 103 /*
 104  * Enter an RCU read-side critical section.
 105  *
 106  * The first cmm_barrier() call ensures that the compiler does not reorder
 107  * the body of _rcu_read_lock() with a mutex.
 108  *
 109  * This function and its helper are both less than 10 lines long.  The
 110  * intent is that this function meets the 10-line criterion in LGPL,
 111  * allowing this function to be invoked directly from non-LGPL code.
 112  */
 113 static inline void _urcu_memb_read_lock(void)
 114 {
 115         unsigned long tmp;
 116
 117         urcu_assert_debug(URCU_TLS(urcu_memb_reader).registered);
 118         cmm_barrier();
 119         tmp = URCU_TLS(urcu_memb_reader).ctr;
 120         urcu_assert_debug((tmp & URCU_GP_CTR_NEST_MASK) != URCU_GP_CTR_NEST_MASK);
 121         _urcu_memb_read_lock_update(tmp);
 122 }
 123
 124 /*
 125  * This is a helper function for _rcu_read_unlock().
 126  *
 127  * The first smp_mb_slave() call ensures that the critical section is
 128  * seen to precede the store to rcu_reader.ctr.
 129  * The second smp_mb_slave() call ensures that we write to rcu_reader.ctr
 130  * before reading the update-side futex.
 131  */
 132 static inline void _urcu_memb_read_unlock_update_and_wakeup(unsigned long tmp)
 133 {
 134         if (caa_likely((tmp & URCU_GP_CTR_NEST_MASK) == URCU_GP_COUNT)) {
 135                 urcu_memb_smp_mb_slave();
 136                 _CMM_STORE_SHARED(URCU_TLS(urcu_memb_reader).ctr, tmp - URCU_GP_COUNT);
 137                 urcu_memb_smp_mb_slave();
 138                 urcu_common_wake_up_gp(&urcu_memb_gp);
 139         } else
 140                 _CMM_STORE_SHARED(URCU_TLS(urcu_memb_reader).ctr, tmp - URCU_GP_COUNT);
 141 }
 142
 143 /*
 144  * Exit an RCU read-side critical section.  Both this function and its
 145  * helper are smaller than 10 lines of code, and are intended to be
 146  * usable by non-LGPL code, as called out in LGPL.
 147  */
 148 static inline void _urcu_memb_read_unlock(void)
 149 {
 150         unsigned long tmp;
 151
 152         urcu_assert_debug(URCU_TLS(urcu_memb_reader).registered);
 153         tmp = URCU_TLS(urcu_memb_reader).ctr;
 154         urcu_assert_debug(tmp & URCU_GP_CTR_NEST_MASK);
 155         _urcu_memb_read_unlock_update_and_wakeup(tmp);
 156         cmm_barrier();  /* Ensure the compiler does not reorder us with mutex */
 157 }
 158
 159 /*
 160  * Returns whether within a RCU read-side critical section.
 161  *
 162  * This function is less than 10 lines long.  The intent is that this
 163  * function meets the 10-line criterion for LGPL, allowing this function
 164  * to be invoked directly from non-LGPL code.
 165  */
 166 static inline int _urcu_memb_read_ongoing(void)
 167 {
 168         return URCU_TLS(urcu_memb_reader).ctr & URCU_GP_CTR_NEST_MASK;
 169 }
 170
 171 #ifdef __cplusplus
 172 }
 173 #endif
 174
 175 #endif /* _URCU_MEMB_STATIC_H */