1  /* Copyright (C) 2010-2023 Free Software Foundation, Inc.
       2     Contributed by ARM Ltd.
       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  /* Provide target-specific access to the futex system call.  */
      27  
      28  /* The include file hierachy above us (wait.h) has pushed visibility
      29     hidden, this will be applied to prototypes with headers we include
      30     with the effect that we cannot link against an external function
      31     (syscall). The solution here is to push default visibility, include
      32     our required headers then reinstante the original visibility.  */
      33  
      34  #pragma GCC visibility push(default)
      35  
      36  #define _GNU_SOURCE 
      37  #include <unistd.h>
      38  #include <sys/syscall.h>
      39  
      40  #pragma GCC visibility pop
      41  
      42  static inline void
      43  futex_wait (int *addr, int val)
      44  {
      45    int err = syscall (SYS_futex, addr, gomp_futex_wait, val, NULL);
      46    if (__builtin_expect (err < 0 && errno == ENOSYS, 0))
      47      {
      48        gomp_futex_wait &= ~FUTEX_PRIVATE_FLAG;
      49        gomp_futex_wake &= ~FUTEX_PRIVATE_FLAG;
      50        syscall (SYS_futex, addr, gomp_futex_wait, val, NULL);
      51      }
      52  }
      53  
      54  static inline void
      55  futex_wake (int *addr, int count)
      56  {
      57    int err = syscall (SYS_futex, addr, gomp_futex_wake, count);
      58    if (__builtin_expect (err < 0 && errno == ENOSYS, 0))
      59      {
      60        gomp_futex_wait &= ~FUTEX_PRIVATE_FLAG;
      61        gomp_futex_wake &= ~FUTEX_PRIVATE_FLAG;
      62        syscall (SYS_futex, addr, gomp_futex_wake, count);
      63      }
      64  }
      65  
      66  static inline void
      67  cpu_relax (void)
      68  {
      69    __asm volatile ("" : : : "memory");
      70  }