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/* $Id: RTSemEventGetResolution-nt.cpp $ */
/** @file
* IPRT - Single Release Event Semaphores, RTSemEventGetResolution.
*/
/*
* Copyright (C) 2006-2023 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
*/
/*********************************************************************************************************************************
* Header Files *
*********************************************************************************************************************************/
#define RTSEMEVENT_WITHOUT_REMAPPING
#ifdef IN_RING0
# include "../r0drv/nt/the-nt-kernel.h"
#else
# include <iprt/nt/nt.h>
#endif
#include <iprt/semaphore.h>
#include <iprt/assert.h>
#include <iprt/timer.h>
#ifdef IN_RING3
# include <iprt/system.h>
#endif
RTDECL(uint32_t) RTSemEventGetResolution(void)
{
/*
* We need to figure the KeWaitForSingleObject / NtWaitForSingleObject timeout
* resolution, i.e. if we wish to wait for 1000ns how long are we likely to
* actually wait before woken up.
*
* In older versions of NT, these timeout were implemented using KTIMERs and
* have the same resolution as what them. This should be found using
* ExSetTimerResolution or NtQueryTimerResolution.
*
* Probably since windows 8.1 the value returned by NtQueryTimerResolution (and
* set NtSetTimerResolution) have been virtualized and no longer reflects the
* timer wheel resolution, at least from what I can tell. ExSetTimerResolution
* still works as before, but it accesses variable that I cannot find out how
* to access from user land. So, kernel will get (and be able to set) the right
* granularity, while in user land we'll be forced to reporting the max value.
*
* (The reason why I suspect it's since 8.1 is because the high resolution
* ExSetTimer APIs were introduced back then.)
*/
#ifdef IN_RING0
return RTTimerGetSystemGranularity();
#else
ULONG cNtTicksMin = 0;
ULONG cNtTicksMax = 0;
ULONG cNtTicksCur = 0;
NTSTATUS rcNt = NtQueryTimerResolution(&cNtTicksMin, &cNtTicksMax, &cNtTicksCur);
if (NT_SUCCESS(rcNt))
{
Assert(cNtTicksMin >= cNtTicksMax);
if (RTSystemGetNtVersion() >= RTSYSTEM_MAKE_NT_VERSION(6,3,9600)) /** @todo check when the switch happened, might be much later... */
return cNtTicksMin * 100;
return cNtTicksCur * 100;
}
AssertFailed();
return 16 * RT_NS_1MS; /* the default on 64-bit windows 10 */
#endif
}
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