libgomp/config/linux/bar.h

   1 /* Copyright (C) 2005-2013 Free Software Foundation, Inc.
   2    Contributed by Richard Henderson <rth@redhat.com>.
   3
   4    This file is part of the GNU OpenMP Library (libgomp).
   5
   6    Libgomp is free software; you can redistribute it and/or modify it
   7    under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3, or (at your option)
   9    any later version.
  10
  11    Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
  12    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  13    FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  14    more details.
  15
  16    Under Section 7 of GPL version 3, you are granted additional
  17    permissions described in the GCC Runtime Library Exception, version
  18    3.1, as published by the Free Software Foundation.
  19
  20    You should have received a copy of the GNU General Public License and
  21    a copy of the GCC Runtime Library Exception along with this program;
  22    see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23    <http://www.gnu.org/licenses/>.  */
  24
  25 /* This is a Linux specific implementation of a barrier synchronization
  26    mechanism for libgomp.  This type is private to the library.  This
  27    implementation uses atomic instructions and the futex syscall.  */
  28
  29 #ifndef GOMP_BARRIER_H
  30 #define GOMP_BARRIER_H 1
  31
  32 #include "mutex.h"
  33
  34 typedef struct
  35 {
  36   /* Make sure total/generation is in a mostly read cacheline, while
  37      awaited in a separate cacheline.  */
  38   unsigned total __attribute__((aligned (64)));
  39   unsigned generation;
  40   unsigned awaited __attribute__((aligned (64)));
  41 } gomp_barrier_t;
  42 typedef unsigned int gomp_barrier_state_t;
  43
  44 static inline void gomp_barrier_init (gomp_barrier_t *bar, unsigned count)
  45 {
  46   bar->total = count;
  47   bar->awaited = count;
  48   bar->generation = 0;
  49 }
  50
  51 static inline void gomp_barrier_reinit (gomp_barrier_t *bar, unsigned count)
  52 {
  53   __atomic_add_fetch (&bar->awaited, count - bar->total, MEMMODEL_ACQ_REL);
  54   bar->total = count;
  55 }
  56
  57 static inline void gomp_barrier_destroy (gomp_barrier_t *bar)
  58 {
  59 }
  60
  61 extern void gomp_barrier_wait (gomp_barrier_t *);
  62 extern void gomp_barrier_wait_last (gomp_barrier_t *);
  63 extern void gomp_barrier_wait_end (gomp_barrier_t *, gomp_barrier_state_t);
  64 extern void gomp_team_barrier_wait (gomp_barrier_t *);
  65 extern void gomp_team_barrier_wait_end (gomp_barrier_t *,
  66                                         gomp_barrier_state_t);
  67 extern void gomp_team_barrier_wake (gomp_barrier_t *, int);
  68
  69 static inline gomp_barrier_state_t
  70 gomp_barrier_wait_start (gomp_barrier_t *bar)
  71 {
  72   unsigned int ret = __atomic_load_n (&bar->generation, MEMMODEL_ACQUIRE) & ~3;
  73   /* A memory barrier is needed before exiting from the various forms
  74      of gomp_barrier_wait, to satisfy OpenMP API version 3.1 section
  75      2.8.6 flush Construct, which says there is an implicit flush during
  76      a barrier region.  This is a convenient place to add the barrier,
  77      so we use MEMMODEL_ACQ_REL here rather than MEMMODEL_ACQUIRE.  */
  78   ret += __atomic_add_fetch (&bar->awaited, -1, MEMMODEL_ACQ_REL) == 0;
  79   return ret;
  80 }
  81
  82 static inline bool
  83 gomp_barrier_last_thread (gomp_barrier_state_t state)
  84 {
  85   return state & 1;
  86 }
  87
  88 /* All the inlines below must be called with team->task_lock
  89    held.  */
  90
  91 static inline void
  92 gomp_team_barrier_set_task_pending (gomp_barrier_t *bar)
  93 {
  94   bar->generation |= 1;
  95 }
  96
  97 static inline void
  98 gomp_team_barrier_clear_task_pending (gomp_barrier_t *bar)
  99 {
 100   bar->generation &= ~1;
 101 }
 102
 103 static inline void
 104 gomp_team_barrier_set_waiting_for_tasks (gomp_barrier_t *bar)
 105 {
 106   bar->generation |= 2;
 107 }
 108
 109 static inline bool
 110 gomp_team_barrier_waiting_for_tasks (gomp_barrier_t *bar)
 111 {
 112   return (bar->generation & 2) != 0;
 113 }
 114
 115 static inline void
 116 gomp_team_barrier_done (gomp_barrier_t *bar, gomp_barrier_state_t state)
 117 {
 118   bar->generation = (state & ~3) + 4;
 119 }
 120
 121 #endif /* GOMP_BARRIER_H */