145 lines
3.3 KiB
C++
145 lines
3.3 KiB
C++
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//+------------------------------------------------------------
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//
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// Copyright (C) 1998, Microsoft Corporation
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//
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// File: spinlock.cpp
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//
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// Contents: Simple Spinlock package used by CLdapConnection
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//
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// Classes:
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//
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// Functions:
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// AcquireSpinLockSingleProc
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// AcquireSpinLockMultiProc
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// InitializeSpinLock
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// ReleaseSpinLock
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//
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// History:
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// jstamerj 980511 17:26:26: Created.
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//
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//-------------------------------------------------------------
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#include "smtpinc.h"
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#include "spinlock.h"
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PFN_ACQUIRESPINLOCK g_AcquireSpinLock;
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//+----------------------------------------------------------------------------
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//
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// Function: InitializeSpinLock
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//
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// Synopsis: Initializes a SPIN_LOCK
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//
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// Arguments: [psl] -- Pointer to SPIN_LOCK to initialize
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//
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// Returns: Nothing. *psl is in released state when this functionr returns
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//
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//-----------------------------------------------------------------------------
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VOID InitializeSpinLock(
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PSPIN_LOCK psl)
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{
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*psl = 0;
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if(g_AcquireSpinLock == NULL) {
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// Determine multi or single proc
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SYSTEM_INFO si;
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GetSystemInfo(&si);
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if(si.dwNumberOfProcessors > 1) {
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g_AcquireSpinLock = AcquireSpinLockMultipleProc;
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} else {
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g_AcquireSpinLock = AcquireSpinLockSingleProc;
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}
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}
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}
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//+----------------------------------------------------------------------------
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//
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// Function: AcquireSpinLockMultiProc
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//
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// Synopsis: Acquire a lock, spinning while it is unavailable.
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// Optimized for multi proc machines
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//
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// Arguments: [psl] -- Pointer to SPIN_LOCK to acquire
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//
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// Returns: Nothing. *psl is in acquired state when this function returns
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//
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//-----------------------------------------------------------------------------
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VOID AcquireSpinLockMultipleProc(
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volatile PSPIN_LOCK psl)
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{
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do {
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//
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// Spin while the lock is unavailable
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//
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while (*psl > 0) {
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;
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}
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//
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// Lock just became available, try to grab it
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//
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} while ( InterlockedIncrement(psl) != 1 );
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}
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//+----------------------------------------------------------------------------
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//
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// Function: AcquireSpinLockSingleProc
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//
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// Synopsis: Acquire a lock, spinning while it is unavailable.
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// Optimized for single proc machines
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//
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// Arguments: [psl] -- Pointer to SPIN_LOCK to acquire
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//
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// Returns: Nothing. *psl is in acquired state when this function returns
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//
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//-----------------------------------------------------------------------------
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VOID AcquireSpinLockSingleProc(
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volatile PSPIN_LOCK psl)
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{
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do {
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//
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// Spin while the lock is unavailable
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//
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while (*psl > 0) {
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Sleep(0);
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}
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//
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// Lock just became available, try to grab it
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//
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} while ( InterlockedIncrement(psl) != 1 );
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}
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//+----------------------------------------------------------------------------
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//
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// Function: ReleaseSpinLock
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//
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// Synopsis: Releases an acquired spin lock
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//
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// Arguments: [psl] -- Pointer to SPIN_LOCK to release.
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//
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// Returns: Nothing. *psl is in released state when this function returns
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//
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//-----------------------------------------------------------------------------
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VOID ReleaseSpinLock(
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PSPIN_LOCK psl)
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{
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_ASSERT( *psl > 0 );
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InterlockedExchange( psl, 0 );
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}
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