1  /* Copyright (C) 2005-2023 Free Software Foundation, Inc.
       2     Contributed by Richard Henderson <rth@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  /* Provide target-specific access to the futex system call.  */
      27  
      28  #ifdef __x86_64__
      29  # ifndef SYS_futex
      30  #  define SYS_futex	202
      31  # endif
      32  
      33  static inline long
      34  __futex_wait (int *addr, int futex_op, int val)
      35  {
      36    long res;
      37  
      38    register void *timeout __asm ("r10") = NULL;
      39    __asm volatile ("syscall"
      40  		  : "=a" (res)
      41  		  : "0" (SYS_futex), "D" (addr), "S" (futex_op),
      42  		    "d" (val), "r" (timeout)
      43  		  : "r11", "rcx", "memory");
      44    return res;
      45  }
      46  
      47  static inline long
      48  __futex_wake (int *addr, int futex_op, int count)
      49  {
      50    long res;
      51  
      52    __asm volatile ("syscall"
      53  		  : "=a" (res)
      54  		  : "0" (SYS_futex), "D" (addr), "S" (futex_op),
      55  		    "d" (count)
      56  		  : "r11", "rcx", "memory");
      57    return res;
      58  }
      59  #else
      60  # ifndef SYS_futex
      61  #  define SYS_futex	240
      62  # endif
      63  
      64  static inline long
      65  __futex_wait (int *addr, int futex_op, int val)
      66  {
      67    long res;
      68  
      69    void *timeout = NULL;
      70    __asm volatile ("int $0x80"
      71  		  : "=a" (res)
      72  		  : "0" (SYS_futex), "b" (addr), "c" (futex_op),
      73  		    "d" (val), "S" (timeout)
      74  		  : "memory");
      75    return res;
      76  }
      77  
      78  static inline long
      79  __futex_wake (int *addr, int futex_op, int count)
      80  {
      81    long res;
      82  
      83    __asm volatile ("int $0x80"
      84  		  : "=a" (res)
      85  		  : "0" (SYS_futex), "b" (addr), "c" (futex_op),
      86  		    "d" (count)
      87  		  : "memory");
      88    return res;
      89  }
      90  #endif /* __x86_64__ */
      91  
      92  static inline void
      93  futex_wait (int *addr, int val)
      94  {
      95    long err = __futex_wait (addr, gomp_futex_wait, val);
      96  
      97    if (__builtin_expect (err == -ENOSYS, 0))
      98      {
      99        gomp_futex_wait &= ~FUTEX_PRIVATE_FLAG;
     100        gomp_futex_wake &= ~FUTEX_PRIVATE_FLAG;
     101  
     102        __futex_wait (addr, gomp_futex_wait, val);
     103      }
     104  }
     105  
     106  static inline void
     107  futex_wake (int *addr, int count)
     108  {
     109    long err = __futex_wake (addr, gomp_futex_wake, count);
     110  
     111    if (__builtin_expect (err == -ENOSYS, 0))
     112      {
     113        gomp_futex_wait &= ~FUTEX_PRIVATE_FLAG;
     114        gomp_futex_wake &= ~FUTEX_PRIVATE_FLAG;
     115  
     116        __futex_wake (addr, gomp_futex_wake, count);
     117      }
     118  }
     119  
     120  static inline void
     121  cpu_relax (void)
     122  {
     123    __builtin_ia32_pause ();
     124  }