| 1 | /* $Id: RTSemEventGetResolution-nt.cpp 96407 2022-08-22 17:43:14Z vboxsync $ */
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| 2 | /** @file
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| 3 | * IPRT - Single Release Event Semaphores, RTSemEventGetResolution.
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| 4 | */
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| 5 |
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| 6 | /*
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| 7 | * Copyright (C) 2006-2022 Oracle and/or its affiliates.
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| 8 | *
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| 9 | * This file is part of VirtualBox base platform packages, as
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| 10 | * available from https://www.virtualbox.org.
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| 11 | *
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| 12 | * This program is free software; you can redistribute it and/or
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| 13 | * modify it under the terms of the GNU General Public License
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| 14 | * as published by the Free Software Foundation, in version 3 of the
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| 15 | * License.
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| 16 | *
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| 17 | * This program is distributed in the hope that it will be useful, but
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| 18 | * WITHOUT ANY WARRANTY; without even the implied warranty of
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| 19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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| 20 | * General Public License for more details.
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| 21 | *
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| 22 | * You should have received a copy of the GNU General Public License
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| 23 | * along with this program; if not, see <https://www.gnu.org/licenses>.
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| 24 | *
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| 25 | * The contents of this file may alternatively be used under the terms
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| 26 | * of the Common Development and Distribution License Version 1.0
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| 27 | * (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
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| 28 | * in the VirtualBox distribution, in which case the provisions of the
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| 29 | * CDDL are applicable instead of those of the GPL.
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| 30 | *
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| 31 | * You may elect to license modified versions of this file under the
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| 32 | * terms and conditions of either the GPL or the CDDL or both.
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| 33 | *
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| 34 | * SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
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| 35 | */
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| 36 |
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| 37 |
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| 38 | /*********************************************************************************************************************************
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| 39 | * Header Files *
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| 40 | *********************************************************************************************************************************/
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| 41 | #define RTSEMEVENT_WITHOUT_REMAPPING
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| 42 | #ifdef IN_RING0
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| 43 | # include "../r0drv/nt/the-nt-kernel.h"
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| 44 | #else
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| 45 | # include <iprt/nt/nt.h>
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| 46 | #endif
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| 47 | #include <iprt/semaphore.h>
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| 48 |
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| 49 | #include <iprt/assert.h>
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| 50 | #include <iprt/timer.h>
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| 51 | #ifdef IN_RING3
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| 52 | # include <iprt/system.h>
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| 53 | #endif
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| 54 |
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| 55 |
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| 56 | RTDECL(uint32_t) RTSemEventGetResolution(void)
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| 57 | {
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| 58 | /*
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| 59 | * We need to figure the KeWaitForSingleObject / NtWaitForSingleObject timeout
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| 60 | * resolution, i.e. if we wish to wait for 1000ns how long are we likely to
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| 61 | * actually wait before woken up.
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| 62 | *
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| 63 | * In older versions of NT, these timeout were implemented using KTIMERs and
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| 64 | * have the same resolution as what them. This should be found using
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| 65 | * ExSetTimerResolution or NtQueryTimerResolution.
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| 66 | *
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| 67 | * Probably since windows 8.1 the value returned by NtQueryTimerResolution (and
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| 68 | * set NtSetTimerResolution) have been virtualized and no longer reflects the
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| 69 | * timer wheel resolution, at least from what I can tell. ExSetTimerResolution
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| 70 | * still works as before, but it accesses variable that I cannot find out how
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| 71 | * to access from user land. So, kernel will get (and be able to set) the right
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| 72 | * granularity, while in user land we'll be forced to reporting the max value.
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| 73 | *
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| 74 | * (The reason why I suspect it's since 8.1 is because the high resolution
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| 75 | * ExSetTimer APIs were introduced back then.)
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| 76 | */
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| 77 | #ifdef IN_RING0
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| 78 | return RTTimerGetSystemGranularity();
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| 79 | #else
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| 80 | ULONG cNtTicksMin = 0;
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| 81 | ULONG cNtTicksMax = 0;
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| 82 | ULONG cNtTicksCur = 0;
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| 83 | NTSTATUS rcNt = NtQueryTimerResolution(&cNtTicksMin, &cNtTicksMax, &cNtTicksCur);
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| 84 | if (NT_SUCCESS(rcNt))
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| 85 | {
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| 86 | Assert(cNtTicksMin >= cNtTicksMax);
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| 87 | if (RTSystemGetNtVersion() >= RTSYSTEM_MAKE_NT_VERSION(6,3,9600)) /** @todo check when the switch happened, might be much later... */
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| 88 | return cNtTicksMin * 100;
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| 89 | return cNtTicksCur * 100;
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| 90 | }
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| 91 | AssertFailed();
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| 92 | return 16 * RT_NS_1MS; /* the default on 64-bit windows 10 */
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| 93 | #endif
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| 94 | }
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| 95 |
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