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bar.h revision 1.1.1.8 
      1 /* Copyright (C) 2005-2020 Free Software Foundation, Inc.
      2    Contributed by Richard Henderson <rth (at) redhat.com>.
      3 
      4    This file is part of the GNU Offloading and Multi Processing Library
      5    (libgomp).
      6 
      7    Libgomp is free software; you can redistribute it and/or modify it
      8    under the terms of the GNU General Public License as published by
      9    the Free Software Foundation; either version 3, or (at your option)
     10    any later version.
     11 
     12    Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
     13    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
     14    FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
     15    more details.
     16 
     17    Under Section 7 of GPL version 3, you are granted additional
     18    permissions described in the GCC Runtime Library Exception, version
     19    3.1, as published by the Free Software Foundation.
     20 
     21    You should have received a copy of the GNU General Public License and
     22    a copy of the GCC Runtime Library Exception along with this program;
     23    see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
     24    <http://www.gnu.org/licenses/>.  */
     25 
     26 /* This is the default implementation of a barrier synchronization mechanism
     27    for libgomp.  This type is private to the library.  Note that we rely on
     28    being able to adjust the barrier count while threads are blocked, so the
     29    POSIX pthread_barrier_t won't work.  */
     30 
     31 #ifndef GOMP_BARRIER_H
     32 #define GOMP_BARRIER_H 1
     33 
     34 #include <pthread.h>
     35 
     36 typedef struct
     37 {
     38   gomp_mutex_t mutex1;
     39 #ifndef HAVE_SYNC_BUILTINS
     40   gomp_mutex_t mutex2;
     41 #endif
     42   gomp_sem_t sem1;
     43   gomp_sem_t sem2;
     44   unsigned total;
     45   unsigned arrived;
     46   unsigned generation;
     47   bool cancellable;
     48 } gomp_barrier_t;
     49 
     50 typedef unsigned int gomp_barrier_state_t;
     51 
     52 /* The generation field contains a counter in the high bits, with a few
     53    low bits dedicated to flags.  Note that TASK_PENDING and WAS_LAST can
     54    share space because WAS_LAST is never stored back to generation.  */
     55 #define BAR_TASK_PENDING	1
     56 #define BAR_WAS_LAST		1
     57 #define BAR_WAITING_FOR_TASK	2
     58 #define BAR_CANCELLED		4
     59 #define BAR_INCR		8
     60 
     61 extern void gomp_barrier_init (gomp_barrier_t *, unsigned);
     62 extern void gomp_barrier_reinit (gomp_barrier_t *, unsigned);
     63 extern void gomp_barrier_destroy (gomp_barrier_t *);
     64 
     65 extern void gomp_barrier_wait (gomp_barrier_t *);
     66 extern void gomp_barrier_wait_end (gomp_barrier_t *, gomp_barrier_state_t);
     67 extern void gomp_team_barrier_wait (gomp_barrier_t *);
     68 extern void gomp_team_barrier_wait_end (gomp_barrier_t *,
     69 					gomp_barrier_state_t);
     70 extern bool gomp_team_barrier_wait_cancel (gomp_barrier_t *);
     71 extern bool gomp_team_barrier_wait_cancel_end (gomp_barrier_t *,
     72 					       gomp_barrier_state_t);
     73 extern void gomp_team_barrier_wake (gomp_barrier_t *, int);
     74 struct gomp_team;
     75 extern void gomp_team_barrier_cancel (struct gomp_team *);
     76 
     77 static inline gomp_barrier_state_t
     78 gomp_barrier_wait_start (gomp_barrier_t *bar)
     79 {
     80   unsigned int ret;
     81   gomp_mutex_lock (&bar->mutex1);
     82   ret = bar->generation & (-BAR_INCR | BAR_CANCELLED);
     83   if (++bar->arrived == bar->total)
     84     ret |= BAR_WAS_LAST;
     85   return ret;
     86 }
     87 
     88 static inline gomp_barrier_state_t
     89 gomp_barrier_wait_cancel_start (gomp_barrier_t *bar)
     90 {
     91   unsigned int ret;
     92   gomp_mutex_lock (&bar->mutex1);
     93   ret = bar->generation & (-BAR_INCR | BAR_CANCELLED);
     94   if (ret & BAR_CANCELLED)
     95     return ret;
     96   if (++bar->arrived == bar->total)
     97     ret |= BAR_WAS_LAST;
     98   return ret;
     99 }
    100 
    101 static inline void
    102 gomp_team_barrier_wait_final (gomp_barrier_t *bar)
    103 {
    104   gomp_team_barrier_wait (bar);
    105 }
    106 
    107 static inline bool
    108 gomp_barrier_last_thread (gomp_barrier_state_t state)
    109 {
    110   return state & BAR_WAS_LAST;
    111 }
    112 
    113 static inline void
    114 gomp_barrier_wait_last (gomp_barrier_t *bar)
    115 {
    116   gomp_barrier_wait (bar);
    117 }
    118 
    119 /* All the inlines below must be called with team->task_lock
    120    held.  */
    121 
    122 static inline void
    123 gomp_team_barrier_set_task_pending (gomp_barrier_t *bar)
    124 {
    125   bar->generation |= BAR_TASK_PENDING;
    126 }
    127 
    128 static inline void
    129 gomp_team_barrier_clear_task_pending (gomp_barrier_t *bar)
    130 {
    131   bar->generation &= ~BAR_TASK_PENDING;
    132 }
    133 
    134 static inline void
    135 gomp_team_barrier_set_waiting_for_tasks (gomp_barrier_t *bar)
    136 {
    137   bar->generation |= BAR_WAITING_FOR_TASK;
    138 }
    139 
    140 static inline bool
    141 gomp_team_barrier_waiting_for_tasks (gomp_barrier_t *bar)
    142 {
    143   return (bar->generation & BAR_WAITING_FOR_TASK) != 0;
    144 }
    145 
    146 static inline bool
    147 gomp_team_barrier_cancelled (gomp_barrier_t *bar)
    148 {
    149   return __builtin_expect ((bar->generation & BAR_CANCELLED) != 0, 0);
    150 }
    151 
    152 static inline void
    153 gomp_team_barrier_done (gomp_barrier_t *bar, gomp_barrier_state_t state)
    154 {
    155   bar->generation = (state & -BAR_INCR) + BAR_INCR;
    156 }
    157 
    158 #endif /* GOMP_BARRIER_H */
    159