futex.h revision 1.1.1.7 
1/* Copyright (C) 2005-2017 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#include <sys/syscall.h>
29
30
31
32static inline long
33sys_futex0(int *addr, int op, int val)
34{
35  register long out0 asm ("out0") = (long) addr;
36  register long out1 asm ("out1") = op;
37  register long out2 asm ("out2") = val;
38  register long out3 asm ("out3") = 0;
39  register long r8 asm ("r8");
40  register long r10 asm ("r10");
41  register long r15 asm ("r15") = SYS_futex;
42
43  __asm __volatile ("break 0x100000"
44	: "=r"(r15), "=r"(out0), "=r"(out1), "=r"(out2), "=r"(out3),
45	  "=r"(r8), "=r"(r10)
46	: "r"(r15), "r"(out0), "r"(out1), "r"(out2), "r"(out3)
47	: "memory", "out4", "out5", "out6", "out7",
48	  /* Non-stacked integer registers, minus r8, r10, r15.  */
49	  "r2", "r3", "r9", "r11", "r12", "r13", "r14", "r16", "r17", "r18",
50	  "r19", "r20", "r21", "r22", "r23", "r24", "r25", "r26", "r27",
51	  "r28", "r29", "r30", "r31",
52	  /* Predicate registers.  */
53	  "p6", "p7", "p8", "p9", "p10", "p11", "p12", "p13", "p14", "p15",
54	  /* Non-rotating fp registers.  */
55	  "f6", "f7", "f8", "f9", "f10", "f11", "f12", "f13", "f14", "f15",
56	  /* Branch registers.  */
57	  "b6");
58  return r8 & r10;
59}
60
61static inline void
62futex_wait (int *addr, int val)
63{
64  long err = sys_futex0 (addr, gomp_futex_wait, val);
65  if (__builtin_expect (err == ENOSYS, 0))
66    {
67      gomp_futex_wait &= ~FUTEX_PRIVATE_FLAG;
68      gomp_futex_wake &= ~FUTEX_PRIVATE_FLAG;
69      sys_futex0 (addr, gomp_futex_wait, val);
70    }
71}
72
73static inline void
74futex_wake (int *addr, int count)
75{
76  long err = sys_futex0 (addr, gomp_futex_wake, count);
77  if (__builtin_expect (err == ENOSYS, 0))
78    {
79      gomp_futex_wait &= ~FUTEX_PRIVATE_FLAG;
80      gomp_futex_wake &= ~FUTEX_PRIVATE_FLAG;
81      sys_futex0 (addr, gomp_futex_wake, count);
82    }
83}
84
85static inline void
86cpu_relax (void)
87{
88  __asm volatile ("hint @pause" : : : "memory");
89}
90