libgomp/config/linux/x86/futex.h

   1 /* Copyright (C) 2005-2024 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 }