config/linux/x86/futex.h

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/* Copyright (C) 2005, 2008, 2009 Free Software Foundation, Inc.
   Contributed by Richard Henderson <rth@redhat.com>.

   This file is part of the GNU OpenMP Library (libgomp).

   Libgomp is free software; you can redistribute it and/or modify it
   under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3, or (at your option)
   any later version.

   Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
   FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
   more details.

   Under Section 7 of GPL version 3, you are granted additional
   permissions described in the GCC Runtime Library Exception, version
   3.1, as published by the Free Software Foundation.

   You should have received a copy of the GNU General Public License and
   a copy of the GCC Runtime Library Exception along with this program;
   see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
   <http://www.gnu.org/licenses/>.  */

/* Provide target-specific access to the futex system call.  */

#ifdef __LP64__
# ifndef SYS_futex
#  define SYS_futex 202
# endif

static inline void
futex_wait (int *addr, int val)
{
  register long r10 __asm__("%r10");
  long res;

  r10 = 0;
  __asm volatile ("syscall"
          : "=a" (res)
          : "0" (SYS_futex), "D" (addr), "S" (gomp_futex_wait),
            "d" (val), "r" (r10)
          : "r11", "rcx", "memory");
  if (__builtin_expect (res == -ENOSYS, 0))
    {
      gomp_futex_wait &= ~FUTEX_PRIVATE_FLAG;
      gomp_futex_wake &= ~FUTEX_PRIVATE_FLAG;
      r10 = 0;
      __asm volatile ("syscall"
              : "=a" (res)
              : "0" (SYS_futex), "D" (addr), "S" (gomp_futex_wait),
            "d" (val), "r" (r10)
              : "r11", "rcx", "memory");
    }
}

static inline void
futex_wake (int *addr, int count)
{
  long res;

  __asm volatile ("syscall"
          : "=a" (res)
          : "0" (SYS_futex), "D" (addr), "S" (gomp_futex_wake),
            "d" (count)
          : "r11", "rcx", "memory");
  if (__builtin_expect (res == -ENOSYS, 0))
    {
      gomp_futex_wait &= ~FUTEX_PRIVATE_FLAG;
      gomp_futex_wake &= ~FUTEX_PRIVATE_FLAG;
      __asm volatile ("syscall"
              : "=a" (res)
              : "0" (SYS_futex), "D" (addr), "S" (gomp_futex_wake),
            "d" (count)
              : "r11", "rcx", "memory");
    }
}
#else
# ifndef SYS_futex
#  define SYS_futex 240
# endif

# ifdef __PIC__

static inline long
sys_futex0 (int *addr, int op, int val)
{
  long res;

  __asm volatile ("xchgl\t%%ebx, %2\n\t"
          "int\t$0x80\n\t"
          "xchgl\t%%ebx, %2"
          : "=a" (res)
          : "0"(SYS_futex), "r" (addr), "c"(op),
            "d"(val), "S"(0)
          : "memory");
  return res;
}

# else

static inline long
sys_futex0 (int *addr, int op, int val)
{
  long res;

  __asm volatile ("int $0x80"
          : "=a" (res)
          : "0"(SYS_futex), "b" (addr), "c"(op),
            "d"(val), "S"(0)
          : "memory");
  return res;
}

# endif /* __PIC__ */

static inline void
futex_wait (int *addr, int val)
{
  long res = sys_futex0 (addr, gomp_futex_wait, val);
  if (__builtin_expect (res == -ENOSYS, 0))
    {
      gomp_futex_wait &= ~FUTEX_PRIVATE_FLAG;
      gomp_futex_wake &= ~FUTEX_PRIVATE_FLAG;
      sys_futex0 (addr, gomp_futex_wait, val);
    }
}

static inline void
futex_wake (int *addr, int count)
{
  long res = sys_futex0 (addr, gomp_futex_wake, count);
  if (__builtin_expect (res == -ENOSYS, 0))
    {
      gomp_futex_wait &= ~FUTEX_PRIVATE_FLAG;
      gomp_futex_wake &= ~FUTEX_PRIVATE_FLAG;
      sys_futex0 (addr, gomp_futex_wake, count);
    }
}

#endif /* __LP64__ */

static inline void
cpu_relax (void)
{
  __asm volatile ("rep; nop" : : : "memory");
}

static inline void
atomic_write_barrier (void)
{
  __sync_synchronize ();
}

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