Question

Why does this code cause a deadlock?

THREAD 1:

EnterCriticalSection( &lock_ );

... Create thread 1

EnterCriticalSection( &lock_ );
while (pred) {
    SleepConditionVariableCs( &cond_, &lock_ );
    // At this point, I would expect thread #2 to wake up, but it doesn't.
}
LeaveCriticalSection( &lock_ );
LeaveCriticalSEction( &lock_ );

THREAD 2:

EnterCriticalSection( &lock_ );

// This never runs
... Do something else for a while

LeaveCriticalSection( &lock_ );

According to the Win32 API, EnterCriticalSection can be called twice in a row from the same thread without deadlocking. It appears that SleepConditionVariableCS only unlocks the critical section once, which means that thread #2 will never run. Is my reasoning correct here?

Basically, what I want is something like Java’s ReentrantLock. What’s the difference between ReentrantLock and CRITICAL_SECTION?

Answer 1

It appears that SleepConditionVariableCS only unlocks the critical section once, which means that thread #2 will never run.