include/urcu/static/urcu-common.h

   1 #ifndef _URCU_COMMON_STATIC_H
   2 #define _URCU_COMMON_STATIC_H
   3
   4 /*
   5  * urcu-common-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/config.h>
  38 #include <urcu/compiler.h>
  39 #include <urcu/arch.h>
  40 #include <urcu/system.h>
  41 #include <urcu/uatomic.h>
  42 #include <urcu/list.h>
  43 #include <urcu/futex.h>
  44 #include <urcu/tls-compat.h>
  45 #include <urcu/debug.h>
  46
  47 #ifdef __cplusplus
  48 extern "C" {
  49 #endif
  50
  51 enum urcu_state {
  52         URCU_READER_ACTIVE_CURRENT,
  53         URCU_READER_ACTIVE_OLD,
  54         URCU_READER_INACTIVE,
  55 };
  56
  57 /*
  58  * The trick here is that URCU_GP_CTR_PHASE must be a multiple of 8 so
  59  * we can use a full 8-bits, 16-bits or 32-bits bitmask for the lower
  60  * order bits.
  61  */
  62 #define URCU_GP_COUNT           (1UL << 0)
  63 /* Use the amount of bits equal to half of the architecture long size */
  64 #define URCU_GP_CTR_PHASE       (1UL << (sizeof(unsigned long) << 2))
  65 #define URCU_GP_CTR_NEST_MASK   (URCU_GP_CTR_PHASE - 1)
  66
  67 struct urcu_gp {
  68         /*
  69          * Global grace period counter.
  70          * Contains the current URCU_GP_CTR_PHASE.
  71          * Also has a URCU_GP_COUNT of 1, to accelerate the reader fast path.
  72          * Written to only by writer with mutex taken.
  73          * Read by both writer and readers.
  74          */
  75         unsigned long ctr;
  76
  77         int32_t futex;
  78 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
  79
  80 struct urcu_reader {
  81         /* Data used by both reader and synchronize_rcu() */
  82         unsigned long ctr;
  83         char need_mb;
  84         /* Data used for registry */
  85         struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
  86         pthread_t tid;
  87         /* Reader registered flag, for internal checks. */
  88         unsigned int registered:1;
  89 };
  90
  91 /*
  92  * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
  93  */
  94 static inline void urcu_common_wake_up_gp(struct urcu_gp *gp)
  95 {
  96         if (caa_unlikely(uatomic_read(&gp->futex) == -1)) {
  97                 uatomic_set(&gp->futex, 0);
  98                 /*
  99                  * Ignoring return value until we can make this function
 100                  * return something (because urcu_die() is not publicly
 101                  * exposed).
 102                  */
 103                 (void) futex_async(&gp->futex, FUTEX_WAKE, 1,
 104                                 NULL, NULL, 0);
 105         }
 106 }
 107
 108 static inline enum urcu_state urcu_common_reader_state(struct urcu_gp *gp,
 109                 unsigned long *ctr)
 110 {
 111         unsigned long v;
 112
 113         /*
 114          * Make sure both tests below are done on the same version of *value
 115          * to insure consistency.
 116          */
 117         v = CMM_LOAD_SHARED(*ctr);
 118         if (!(v & URCU_GP_CTR_NEST_MASK))
 119                 return URCU_READER_INACTIVE;
 120         if (!((v ^ gp->ctr) & URCU_GP_CTR_PHASE))
 121                 return URCU_READER_ACTIVE_CURRENT;
 122         return URCU_READER_ACTIVE_OLD;
 123 }
 124
 125 #ifdef __cplusplus
 126 }
 127 #endif
 128
 129 #endif /* _URCU_COMMON_STATIC_H */