155 lines
3.8 KiB
C
155 lines
3.8 KiB
C
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//////////////////////////////////////////////////////////////////////////////
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//
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// Copyright (c) 1999-2000 Microsoft Corporation
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//
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// Module Name:
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// SpinLock.h
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//
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// Description:
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// Spin Lock implementation.
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//
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// Maintained By:
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// Geoffrey Pease (GPease) 27-NOV-1999
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//
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//////////////////////////////////////////////////////////////////////////////
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#pragma once
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// CSpinLock
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class
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CSpinLock
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{
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private: // Data
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LONG * m_plLock; // pointer to the lock
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LONG m_lSpinCount; // counts the number of sleeps
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LONG m_lTimeout; // count until acquire lock fails
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#if DBG==1
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BOOL m_fAcquired; // DEBUG: internal state of the lock
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BOOL m_fAcquiredOnce; // DEBUG: lock was acquired at least once.
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#endif
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public: // Methods
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explicit
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CSpinLock( LONG * plLock, LONG lTimeout ) :
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m_plLock( plLock ),
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m_lTimeout( lTimeout )
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{
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Assert( m_lTimeout >= 0 || m_lTimeout == INFINITE );
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#if DBG==1
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m_fAcquired = FALSE;
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m_fAcquiredOnce = FALSE;
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#endif
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};
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//
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~CSpinLock()
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{
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#if DBG==1
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AssertMsg( m_fAcquired == FALSE, "Lock was not released!" );
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AssertMsg( m_fAcquiredOnce != FALSE, "Lock was never acquired. Why was I needed?" );
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#endif
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};
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//////////////////////////////////////////////////////////////////////////
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//
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// HRESULT
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// AcquireLock( void )
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//
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// Description:
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// Acquires the spin lock. Does not return until the lock is
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// acquired.
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//
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// Arguments:
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// None.
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//
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// Return Values:
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// S_OK - Sucess.
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// HRESULT_FROM_WIN32( ERROR_LOCK_FAILED ) - Lock failed.
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//
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//////////////////////////////////////////////////////////////////////////
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HRESULT
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AcquireLock( void )
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{
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HRESULT hr;
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LONG l = TRUE;
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#if DBG==1
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AssertMsg( m_fAcquired == FALSE, "Trying to acquire a lock that it already own. Thread is going to freeze up." );
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m_fAcquiredOnce = TRUE;
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#endif
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m_lSpinCount = 0;
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for(;;)
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{
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l = InterlockedCompareExchange( m_plLock, TRUE, FALSE );
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if ( l == FALSE )
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{
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//
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// Lock acquired.
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//
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hr = S_OK;
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break;
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} // if: got lock
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else
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{
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m_lSpinCount++;
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if ( m_lSpinCount > m_lTimeout )
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{
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AssertMsg( m_lSpinCount >= 0, "This lock doesn't seem to have been released properly." );
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if ( m_lTimeout != INFINITE )
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{
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hr = THR( HRESULT_FROM_WIN32( ERROR_LOCK_FAILED ) );
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break;
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} // if: not infinite
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} // if: count exceeded
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//
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// Put a breakpoint here if you think that someone is double
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// locking.
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//
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Sleep( 1 );
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} // if: lock not acquired
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} // for: forever
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#if DBG==1
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m_fAcquired = TRUE;
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#endif
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return hr;
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}; // AcquireLock( )
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//////////////////////////////////////////////////////////////////////////
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//
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// HRESULT
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// ReleaseLock( void )
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//
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// Description:
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// Releases the spin lock. Return immediately.
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//
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// Arguments:
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// None.
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//
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// Return Values:
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// S_OK - Success.
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//
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//////////////////////////////////////////////////////////////////////////
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HRESULT
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ReleaseLock( void )
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{
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#if DBG==1
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AssertMsg( m_fAcquired == TRUE, "Releasing a lock that was not owned." );
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#endif
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*m_plLock = FALSE;
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#if DBG==1
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m_fAcquired = FALSE;
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#endif
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return S_OK;
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}; // ReleaseLock( )
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}; // class CSpinLock
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