//-----------------------------------------------------------------
// Acquire the lock.
//-----------------------------------------------------------------
void CrstBase::Enter()
{
#ifdef _DEBUG
PreEnter ();
#endif
_ASSERTE(IsSafeToTake() || g_fEEShutDown);
#ifdef _DEBUG
char buffer[100];
sprintf(buffer, "Enter in crst.h - %s", m_tag);
CRSTBLOCKCOUNTINCL();
LOCKCOUNTINCL(buffer);
#endif
EnterCriticalSection(&m_criticalsection);
CRSTELOCKCOUNTINCL();
#ifdef _DEBUG
m_holderthreadid = GetCurrentThreadId();
m_entercount++;
PostEnter ();
#endif
}
//=====================================================================
BOOL SimpleRWLock::TryEnterWrite()
{
STATIC_CONTRACT_NOTHROW;
STATIC_CONTRACT_CAN_TAKE_LOCK;
#ifdef _DEBUG
PreEnter();
#endif //_DEBUG
LONG RWLock = InterlockedCompareExchange( &m_RWLock, -1, 0 );
_ASSERTE (RWLock >= 0 || RWLock == -1);
if( RWLock ) {
return FALSE;
}
INCTHREADLOCKCOUNT();
EE_LOCK_TAKEN(this);
#ifdef _DEBUG
PostEnter();
#endif //_DEBUG
ResetWriterWaiting();
return TRUE;
}
BOOL SimpleRWLock::TryEnterRead()
{
STATIC_CONTRACT_NOTHROW;
STATIC_CONTRACT_CAN_TAKE_LOCK;
#ifdef _DEBUG
PreEnter();
#endif //_DEBUG
LONG RWLock;
do {
RWLock = m_RWLock;
if( RWLock == -1 ) return FALSE;
_ASSERTE (RWLock >= 0);
} while( RWLock != InterlockedCompareExchange( &m_RWLock, RWLock+1, RWLock ));
INCTHREADLOCKCOUNT();
EE_LOCK_TAKEN(this);
#ifdef _DEBUG
PostEnter();
#endif //_DEBUG
return TRUE;
}
//=====================================================================
void SimpleRWLock::EnterRead()
{
STATIC_CONTRACT_NOTHROW;
STATIC_CONTRACT_CAN_TAKE_LOCK;
// Custom contract is needed for PostEnter()'s unscoped GC_NoTrigger counter change
#ifdef ENABLE_CONTRACTS_IMPL
CheckGCNoTrigger();
#endif //ENABLE_CONTRACTS_IMPL
GCX_MAYBE_PREEMP(m_gcMode == PREEMPTIVE);
#ifdef _DEBUG
PreEnter();
#endif //_DEBUG
DWORD dwSwitchCount = 0;
while (TRUE)
{
// prevent writers from being starved. This assumes that writers are rare and
// dont hold the lock for a long time.
while (IsWriterWaiting())
{
int spinCount = m_spinCount;
while (spinCount > 0) {
spinCount--;
YieldProcessor();
}
__SwitchToThread(0, ++dwSwitchCount);
}
if (TryEnterRead())
{
return;
}
DWORD i = g_SpinConstants.dwInitialDuration;
do
{
if (TryEnterRead())
{
return;
}
if (g_SystemInfo.dwNumberOfProcessors <= 1)
{
break;
}
// Delay by approximately 2*i clock cycles (Pentium III).
// This is brittle code - future processors may of course execute this
// faster or slower, and future code generators may eliminate the loop altogether.
// The precise value of the delay is not critical, however, and I can't think
// of a better way that isn't machine-dependent.
for (int delayCount = i; --delayCount; )
{
YieldProcessor(); // indicate to the processor that we are spining
}
// exponential backoff: wait a factor longer in the next iteration
i *= g_SpinConstants.dwBackoffFactor;
}
while (i < g_SpinConstants.dwMaximumDuration);
__SwitchToThread(0, ++dwSwitchCount);
}
}
//=====================================================================
void SimpleRWLock::EnterWrite()
{
STATIC_CONTRACT_NOTHROW;
STATIC_CONTRACT_CAN_TAKE_LOCK;
// Custom contract is needed for PostEnter()'s unscoped GC_NoTrigger counter change
#ifdef ENABLE_CONTRACTS_IMPL
CheckGCNoTrigger();
#endif //ENABLE_CONTRACTS_IMPL
GCX_MAYBE_PREEMP(m_gcMode == PREEMPTIVE);
#ifdef _DEBUG
PreEnter();
#endif //_DEBUG
BOOL set = FALSE;
DWORD dwSwitchCount = 0;
while (TRUE)
{
if (TryEnterWrite())
{
return;
}
// set the writer waiting word, if not already set, to notify potential
// readers to wait. Remember, if the word is set, so it can be reset later.
if (!IsWriterWaiting())
{
SetWriterWaiting();
set = TRUE;
}
DWORD i = g_SpinConstants.dwInitialDuration;
do
{
if (TryEnterWrite())
{
return;
}
if (g_SystemInfo.dwNumberOfProcessors <= 1)
{
break;
}
// Delay by approximately 2*i clock cycles (Pentium III).
// This is brittle code - future processors may of course execute this
// faster or slower, and future code generators may eliminate the loop altogether.
// The precise value of the delay is not critical, however, and I can't think
// of a better way that isn't machine-dependent.
for (int delayCount = i; --delayCount; )
{
YieldProcessor(); // indicate to the processor that we are spining
}
// exponential backoff: wait a factor longer in the next iteration
i *= g_SpinConstants.dwBackoffFactor;
}
while (i < g_SpinConstants.dwMaximumDuration);
__SwitchToThread(0, ++dwSwitchCount);
}
}
