include/urcu/static/urcu-common.h

   1 // SPDX-FileCopyrightText: 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   2 // SPDX-FileCopyrightText: 2009 Paul E. McKenney, IBM Corporation.
   3 //
   4 // SPDX-License-Identifier: LGPL-2.1-or-later
   5
   6 #ifndef _URCU_COMMON_STATIC_H
   7 #define _URCU_COMMON_STATIC_H
   8
   9 /*
  10  * Userspace RCU header.
  11  *
  12  * TO BE INCLUDED ONLY IN CODE THAT IS TO BE RECOMPILED ON EACH LIBURCU
  13  * RELEASE. See urcu.h for linking dynamically with the userspace rcu library.
  14  *
  15  * IBM's contributions to this file may be relicensed under LGPLv2 or later.
  16  */
  17
  18 #include <stdlib.h>
  19 #include <pthread.h>
  20 #include <unistd.h>
  21 #include <stdint.h>
  22
  23 #include <urcu/annotate.h>
  24 #include <urcu/config.h>
  25 #include <urcu/compiler.h>
  26 #include <urcu/arch.h>
  27 #include <urcu/system.h>
  28 #include <urcu/uatomic.h>
  29 #include <urcu/list.h>
  30 #include <urcu/futex.h>
  31 #include <urcu/tls-compat.h>
  32
  33 #ifdef __cplusplus
  34 extern "C" {
  35 #endif
  36
  37 enum urcu_state {
  38         URCU_READER_ACTIVE_CURRENT,
  39         URCU_READER_ACTIVE_OLD,
  40         URCU_READER_INACTIVE,
  41 };
  42
  43 /*
  44  * The trick here is that URCU_GP_CTR_PHASE must be a multiple of 8 so
  45  * we can use a full 8-bits, 16-bits or 32-bits bitmask for the lower
  46  * order bits.
  47  */
  48 #define URCU_GP_COUNT           (1UL << 0)
  49 /* Use the amount of bits equal to half of the architecture long size */
  50 #define URCU_GP_CTR_PHASE       (1UL << (sizeof(unsigned long) << 2))
  51 #define URCU_GP_CTR_NEST_MASK   (URCU_GP_CTR_PHASE - 1)
  52
  53 struct urcu_gp {
  54         /*
  55          * Global grace period counter.
  56          * Contains the current URCU_GP_CTR_PHASE.
  57          * Also has a URCU_GP_COUNT of 1, to accelerate the reader fast path.
  58          * Written to only by writer with mutex taken.
  59          * Read by both writer and readers.
  60          */
  61         unsigned long ctr;
  62
  63         int32_t futex;
  64 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
  65
  66 struct urcu_reader {
  67         /* Data used by both reader and synchronize_rcu() */
  68         unsigned long ctr;
  69         char need_mb;
  70         /* Data used for registry */
  71         struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
  72         pthread_t tid;
  73         /* Reader registered flag, for internal checks. */
  74         unsigned int registered:1;
  75 };
  76
  77 /*
  78  * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
  79  */
  80 static inline void urcu_common_wake_up_gp(struct urcu_gp *gp)
  81 {
  82         if (caa_unlikely(uatomic_read(&gp->futex) == -1)) {
  83                 uatomic_set(&gp->futex, 0);
  84                 /*
  85                  * Ignoring return value until we can make this function
  86                  * return something (because urcu_die() is not publicly
  87                  * exposed).
  88                  */
  89                 (void) futex_async(&gp->futex, FUTEX_WAKE, 1,
  90                                 NULL, NULL, 0);
  91         }
  92 }
  93
  94 static inline enum urcu_state urcu_common_reader_state(struct urcu_gp *gp,
  95                                                 unsigned long *ctr,
  96                                                 cmm_annotate_t *group)
  97 {
  98         unsigned long v;
  99
 100         /*
 101          * Make sure both tests below are done on the same version of *value
 102          * to insure consistency.
 103          */
 104         v = uatomic_load(ctr, CMM_RELAXED);
 105         cmm_annotate_group_mem_acquire(group, ctr);
 106
 107         if (!(v & URCU_GP_CTR_NEST_MASK))
 108                 return URCU_READER_INACTIVE;
 109         if (!((v ^ gp->ctr) & URCU_GP_CTR_PHASE))
 110                 return URCU_READER_ACTIVE_CURRENT;
 111         return URCU_READER_ACTIVE_OLD;
 112 }
 113
 114 #ifdef __cplusplus
 115 }
 116 #endif
 117
 118 #endif /* _URCU_COMMON_STATIC_H */