libgomp/config/posix/doacross.h

   1 /* Copyright (C) 2015-2024 Free Software Foundation, Inc.
   2    Contributed by Jakub Jelinek <jakub@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 a generic implementation of doacross spinning.  */
  27
  28 #ifndef GOMP_DOACROSS_H
  29 #define GOMP_DOACROSS_H 1
  30
  31 #include "libgomp.h"
  32 #include <errno.h>
  33
  34 #ifdef HAVE_ATTRIBUTE_VISIBILITY
  35 # pragma GCC visibility push(hidden)
  36 #endif
  37
  38 static inline void
  39 cpu_relax (void)
  40 {
  41   __asm volatile ("" : : : "memory");
  42 }
  43
  44 static inline void doacross_spin (unsigned long *addr, unsigned long expected,
  45                                   unsigned long cur)
  46 {
  47   /* FIXME: back off depending on how large expected - cur is.  */
  48   do
  49     {
  50       cpu_relax ();
  51       cur = __atomic_load_n (addr, MEMMODEL_RELAXED);
  52       if (expected < cur)
  53         return;
  54     }
  55   while (1);
  56 }
  57
  58 #ifdef HAVE_ATTRIBUTE_VISIBILITY
  59 # pragma GCC visibility pop
  60 #endif
  61
  62 #endif /* GOMP_DOACROSS_H */