| 1 | /* $Id: semwait-linux.h 92779 2021-12-07 09:45:53Z vboxsync $ */
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| 2 | /** @file
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| 3 | * IPRT - Common semaphore wait code, Linux.
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| 4 | */
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| 5 |
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| 6 | /*
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| 7 | * Copyright (C) 2021 Oracle Corporation
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| 8 | *
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| 9 | * This file is part of VirtualBox Open Source Edition (OSE), as
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| 10 | * available from http://www.215389.xyz. This file is free software;
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| 11 | * you can redistribute it and/or modify it under the terms of the GNU
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| 12 | * General Public License (GPL) as published by the Free Software
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| 13 | * Foundation, in version 2 as it comes in the "COPYING" file of the
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| 14 | * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
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| 15 | * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
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| 16 | *
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| 17 | * The contents of this file may alternatively be used under the terms
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| 18 | * of the Common Development and Distribution License Version 1.0
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| 19 | * (CDDL) only, as it comes in the "COPYING.CDDL" file of the
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| 20 | * VirtualBox OSE distribution, in which case the provisions of the
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| 21 | * CDDL are applicable instead of those of the GPL.
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| 22 | *
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| 23 | * You may elect to license modified versions of this file under the
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| 24 | * terms and conditions of either the GPL or the CDDL or both.
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| 25 | */
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| 26 |
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| 27 | #ifndef IPRT_INCLUDED_SRC_r3_linux_semwait_linux_h
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| 28 | #define IPRT_INCLUDED_SRC_r3_linux_semwait_linux_h
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| 29 | #ifndef RT_WITHOUT_PRAGMA_ONCE
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| 30 | # pragma once
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| 31 | #endif
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| 32 |
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| 33 |
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| 34 | /* With 2.6.17 futex.h has become C++ unfriendly, so define the bits we need. */
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| 35 | #define FUTEX_WAIT 0
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| 36 | #define FUTEX_WAKE 1
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| 37 | #define FUTEX_WAIT_BITSET 9 /**< @since 2.6.25 - uses absolute timeout. */
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| 38 |
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| 39 |
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| 40 | /**
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| 41 | * Wrapper for the futex syscall.
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| 42 | */
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| 43 | DECLINLINE(long) sys_futex(uint32_t volatile *uaddr, int op, int val, struct timespec *utime, int32_t *uaddr2, int val3)
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| 44 | {
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| 45 | errno = 0;
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| 46 | long rc = syscall(__NR_futex, uaddr, op, val, utime, uaddr2, val3);
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| 47 | if (rc < 0)
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| 48 | {
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| 49 | Assert(rc == -1);
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| 50 | rc = -errno;
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| 51 | }
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| 52 | return rc;
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| 53 | }
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| 54 |
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| 55 |
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| 56 | DECL_NO_INLINE(static, void) rtSemLinuxCheckForFutexWaitBitSetSlow(int volatile *pfCanUseWaitBitSet)
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| 57 | {
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| 58 | uint32_t uTestVar = UINT32_MAX;
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| 59 | long rc = sys_futex(&uTestVar, FUTEX_WAIT_BITSET, UINT32_C(0xf0f0f0f0), NULL, NULL, UINT32_MAX);
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| 60 | *pfCanUseWaitBitSet = rc == -EAGAIN;
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| 61 | AssertMsg(rc == -ENOSYS || rc == -EAGAIN, ("%d\n", rc));
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| 62 | }
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| 63 |
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| 64 |
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| 65 | DECLINLINE(void) rtSemLinuxCheckForFutexWaitBitSet(int volatile *pfCanUseWaitBitSet)
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| 66 | {
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| 67 | if (*pfCanUseWaitBitSet != -1)
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| 68 | { /* likely */ }
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| 69 | else
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| 70 | rtSemLinuxCheckForFutexWaitBitSetSlow(pfCanUseWaitBitSet);
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| 71 | }
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| 72 |
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| 73 | #endif /* !IPRT_INCLUDED_SRC_r3_linux_semwait_linux_h */
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| 74 |
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