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/* $Id: semwait-linux.h $ */
/** @file
* IPRT - Common semaphore wait code, Linux.
*/
/*
* Copyright (C) 2021-2023 Oracle and/or its affiliates.
*
* This file is part of VirtualBox base platform packages, as
* available from https://www.virtualbox.org.
*
* This program 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, in version 3 of the
* License.
*
* This program 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.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <https://www.gnu.org/licenses>.
*
* The contents of this file may alternatively be used under the terms
* of the Common Development and Distribution License Version 1.0
* (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
* in the VirtualBox distribution, in which case the provisions of the
* CDDL are applicable instead of those of the GPL.
*
* You may elect to license modified versions of this file under the
* terms and conditions of either the GPL or the CDDL or both.
*
* SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
*/
#ifndef IPRT_INCLUDED_SRC_r3_linux_semwait_linux_h
#define IPRT_INCLUDED_SRC_r3_linux_semwait_linux_h
#ifndef RT_WITHOUT_PRAGMA_ONCE
# pragma once
#endif
/* With 2.6.17 futex.h has become C++ unfriendly, so define the bits we need. */
#define FUTEX_WAIT 0
#define FUTEX_WAKE 1
#define FUTEX_WAIT_BITSET 9 /**< @since 2.6.25 - uses absolute timeout. */
/**
* Wrapper for the futex syscall.
*/
DECLINLINE(long) sys_futex(uint32_t volatile *uaddr, int op, int val, struct timespec *utime, int32_t *uaddr2, int val3)
{
errno = 0;
long rc = syscall(__NR_futex, uaddr, op, val, utime, uaddr2, val3);
if (rc < 0)
{
Assert(rc == -1);
rc = -errno;
}
return rc;
}
DECL_NO_INLINE(static, void) rtSemLinuxCheckForFutexWaitBitSetSlow(int volatile *pfCanUseWaitBitSet)
{
uint32_t uTestVar = UINT32_MAX;
long rc = sys_futex(&uTestVar, FUTEX_WAIT_BITSET, UINT32_C(0xf0f0f0f0), NULL, NULL, UINT32_MAX);
*pfCanUseWaitBitSet = rc == -EAGAIN;
AssertMsg(rc == -ENOSYS || rc == -EAGAIN, ("%d\n", rc));
}
DECLINLINE(void) rtSemLinuxCheckForFutexWaitBitSet(int volatile *pfCanUseWaitBitSet)
{
if (*pfCanUseWaitBitSet != -1)
{ /* likely */ }
else
rtSemLinuxCheckForFutexWaitBitSetSlow(pfCanUseWaitBitSet);
}
/**
* Converts a extended wait timeout specification to an timespec and
* corresponding futex operation, as well as an approximate relative nanosecond
* interval.
*
* @note This does not check for RTSEMWAIT_FLAGS_INDEFINITE, caller should've
* done that already.
*
* @returns The relative wait in nanoseconds. 0 for a poll call, UINT64_MAX for
* an effectively indefinite wait.
* @param fFlags RTSEMWAIT_FLAGS_XXX.
* @param fCanUseWaitBitSet Whether we can use FUTEX_WAIT_BITMSET or not.
* @param uTimeout The timeout.
* @param pDeadline Where to return the deadline.
* @param piWaitOp Where to return the FUTEX wait operation number.
* @param puWaitVal3 Where to return the FUTEX wait value 3.
* @param pnsAbsTimeout Where to return the absolute timeout in case of
* a resuming relative call (i.e. FUTEX_WAIT).
*/
DECL_FORCE_INLINE(uint64_t)
rtSemLinuxCalcDeadline(uint32_t fFlags, uint64_t uTimeout, int fCanUseWaitBitSet,
struct timespec *pDeadline, int *piWaitOp, uint32_t *puWaitVal3, uint64_t *pnsAbsTimeout)
{
Assert(!(fFlags & RTSEMWAIT_FLAGS_INDEFINITE));
if (fFlags & RTSEMWAIT_FLAGS_RELATIVE)
{
Assert(!(fFlags & RTSEMWAIT_FLAGS_ABSOLUTE));
/*
* Polling call?
*/
if (uTimeout == 0)
return 0;
/*
* We use FUTEX_WAIT here as it takes a relative timespec.
*
* Note! For non-resuming waits, we can skip calculating the absolute
* time ASSUMING it is only needed for timeout adjustments
* after an -EINTR return.
*/
if (fFlags & RTSEMWAIT_FLAGS_MILLISECS)
{
if ( sizeof(pDeadline->tv_sec) >= sizeof(uint64_t)
|| uTimeout < (uint64_t)UINT32_MAX * RT_MS_1SEC)
{
pDeadline->tv_sec = uTimeout / RT_MS_1SEC;
pDeadline->tv_nsec = (uTimeout % RT_MS_1SEC) & RT_NS_1MS;
uTimeout *= RT_NS_1MS;
}
else
return UINT64_MAX;
}
else
{
Assert(fFlags & RTSEMWAIT_FLAGS_NANOSECS);
if ( sizeof(pDeadline->tv_sec) >= sizeof(uint64_t)
|| uTimeout < (uint64_t)UINT32_MAX * RT_NS_1SEC)
{
pDeadline->tv_sec = uTimeout / RT_NS_1SEC;
pDeadline->tv_nsec = uTimeout % RT_NS_1SEC;
}
else
return UINT64_MAX;
}
#ifdef RT_STRICT
if (!(fFlags & RTSEMWAIT_FLAGS_RESUME))
*pnsAbsTimeout = uTimeout;
else
#endif
*pnsAbsTimeout = RTTimeNanoTS() + uTimeout; /* Note! only relevant for relative waits (FUTEX_WAIT). */
}
else
{
/* Absolute deadline: */
Assert(fFlags & RTSEMWAIT_FLAGS_ABSOLUTE);
if (fCanUseWaitBitSet == true)
{
/*
* Use FUTEX_WAIT_BITSET as it takes an absolute deadline.
*/
if (fFlags & RTSEMWAIT_FLAGS_MILLISECS)
{
if ( sizeof(pDeadline->tv_sec) >= sizeof(uint64_t)
|| uTimeout < (uint64_t)UINT32_MAX * RT_MS_1SEC)
{
pDeadline->tv_sec = uTimeout / RT_MS_1SEC;
pDeadline->tv_nsec = (uTimeout % RT_MS_1SEC) & RT_NS_1MS;
}
else
return UINT64_MAX;
}
else
{
Assert(fFlags & RTSEMWAIT_FLAGS_NANOSECS);
if ( sizeof(pDeadline->tv_sec) >= sizeof(uint64_t)
|| uTimeout < (uint64_t)UINT32_MAX * RT_NS_1SEC)
{
pDeadline->tv_sec = uTimeout / RT_NS_1SEC;
pDeadline->tv_nsec = uTimeout % RT_NS_1SEC;
}
else
return UINT64_MAX;
}
*pnsAbsTimeout = uTimeout;
*piWaitOp = FUTEX_WAIT_BITSET;
*puWaitVal3 = UINT32_MAX;
return RT_MS_1SEC; /* Whatever non-zero; Whole point is not calling RTTimeNanoTS() in this path. */
}
/*
* FUTEX_WAIT_BITSET is not available, so use FUTEX_WAIT with a
* relative timeout.
*/
if (fFlags & RTSEMWAIT_FLAGS_MILLISECS)
{
if (uTimeout < UINT64_MAX / RT_NS_1MS)
uTimeout *= RT_NS_1MS;
else
return UINT64_MAX;
}
uint64_t const u64Now = RTTimeNanoTS();
if (u64Now < uTimeout)
{
*pnsAbsTimeout = uTimeout;
uTimeout -= u64Now;
}
else
return 0;
if ( sizeof(pDeadline->tv_sec) >= sizeof(uint64_t)
|| uTimeout < (uint64_t)UINT32_MAX * RT_NS_1SEC)
{
pDeadline->tv_sec = uTimeout / RT_NS_1SEC;
pDeadline->tv_nsec = uTimeout % RT_NS_1SEC;
}
else
return UINT64_MAX;
}
*piWaitOp = FUTEX_WAIT;
*puWaitVal3 = 0;
return uTimeout;
}
#endif /* !IPRT_INCLUDED_SRC_r3_linux_semwait_linux_h */
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