Why is the following implementation of condition variables wrong? Diagram how a set of threads could interact to achieve an invalid state.

class Condition

{

private: int waiting;

Semaphore *sema;

}

void Condition::Wait(Lock* l)

{

waiting++;

l->Release();

sema->P();

l->Acquire();

}

void Condition::Signal(Lock* l)

{

if (waiting > 0)

{

sema->V();

waiting--;

}

}