VOID
NTAPI
KiQuantumEnd(VOID)
{
PKPRCB Prcb = KeGetCurrentPrcb();
PKTHREAD NextThread, Thread = Prcb->CurrentThread;
/* Check if a DPC Event was requested to be signaled */
if (InterlockedExchange(&Prcb->DpcSetEventRequest, 0))
{
/* Signal it */
KeSetEvent(&Prcb->DpcEvent, 0, 0);
}
/* Raise to synchronization level and lock the PRCB and thread */
KeRaiseIrqlToSynchLevel();
KiAcquireThreadLock(Thread);
KiAcquirePrcbLock(Prcb);
/* Check if Quantum expired */
if (Thread->Quantum <= 0)
{
/* Check if we're real-time and with quantums disabled */
if ((Thread->Priority >= LOW_REALTIME_PRIORITY) &&
(Thread->ApcState.Process->DisableQuantum))
{
/* Otherwise, set maximum quantum */
Thread->Quantum = MAX_QUANTUM;
}
else
{
/* Reset the new Quantum */
Thread->Quantum = Thread->QuantumReset;
/* Calculate new priority */
Thread->Priority = KiComputeNewPriority(Thread, 1);
/* Check if a new thread is scheduled */
if (!Prcb->NextThread)
{
/* Get a new ready thread */
NextThread = KiSelectReadyThread(Thread->Priority, Prcb);
if (NextThread)
{
/* Found one, set it on standby */
NextThread->State = Standby;
Prcb->NextThread = NextThread;
}
}
else
{
/* Otherwise, make sure that this thread doesn't get preempted */
Thread->Preempted = FALSE;
}
}
}
/* Release the thread lock */
KiReleaseThreadLock(Thread);
/* Check if there's no thread scheduled */
if (!Prcb->NextThread)
{
/* Just leave now */
KiReleasePrcbLock(Prcb);
KeLowerIrql(DISPATCH_LEVEL);
return;
}
/* Get the next thread now */
NextThread = Prcb->NextThread;
/* Set current thread's swap busy to true */
KiSetThreadSwapBusy(Thread);
/* Switch threads in PRCB */
Prcb->NextThread = NULL;
Prcb->CurrentThread = NextThread;
/* Set thread to running and the switch reason to Quantum End */
NextThread->State = Running;
Thread->WaitReason = WrQuantumEnd;
/* Queue it on the ready lists */
KxQueueReadyThread(Thread, Prcb);
/* Set wait IRQL to APC_LEVEL */
Thread->WaitIrql = APC_LEVEL;
/* Swap threads */
KiSwapContext(APC_LEVEL, Thread);
/* Lower IRQL back to DISPATCH_LEVEL */
KeLowerIrql(DISPATCH_LEVEL);
}
/*
* @implemented
*/
NTSTATUS
NTAPI
NtYieldExecution(VOID)
{
NTSTATUS Status;
KIRQL OldIrql;
PKPRCB Prcb;
PKTHREAD Thread, NextThread;
/* NB: No instructions (other than entry code) should preceed this line */
/* Fail if there's no ready summary */
if (!KiGetCurrentReadySummary()) return STATUS_NO_YIELD_PERFORMED;
/* Now get the current thread, set the status... */
Status = STATUS_NO_YIELD_PERFORMED;
Thread = KeGetCurrentThread();
/* Raise IRQL to synch and get the KPRCB now */
OldIrql = KeRaiseIrqlToSynchLevel();
Prcb = KeGetCurrentPrcb();
/* Now check if there's still a ready summary */
if (Prcb->ReadySummary)
{
/* Acquire thread and PRCB lock */
KiAcquireThreadLock(Thread);
KiAcquirePrcbLock(Prcb);
/* Find a new thread to run if none was selected */
if (!Prcb->NextThread) Prcb->NextThread = KiSelectReadyThread(1, Prcb);
/* Make sure we still have a next thread to schedule */
NextThread = Prcb->NextThread;
if (NextThread)
{
/* Reset quantum and recalculate priority */
Thread->Quantum = Thread->QuantumReset;
Thread->Priority = KiComputeNewPriority(Thread, 1);
/* Release the thread lock */
KiReleaseThreadLock(Thread);
/* Set context swap busy */
KiSetThreadSwapBusy(Thread);
/* Set the new thread as running */
Prcb->NextThread = NULL;
Prcb->CurrentThread = NextThread;
NextThread->State = Running;
/* Setup a yield wait and queue the thread */
Thread->WaitReason = WrYieldExecution;
KxQueueReadyThread(Thread, Prcb);
/* Make it wait at APC_LEVEL */
Thread->WaitIrql = APC_LEVEL;
/* Sanity check */
ASSERT(OldIrql <= DISPATCH_LEVEL);
/* Swap to new thread */
KiSwapContext(APC_LEVEL, Thread);
Status = STATUS_SUCCESS;
}
else
{
/* Release the PRCB and thread lock */
KiReleasePrcbLock(Prcb);
KiReleaseThreadLock(Thread);
}
}
/* Lower IRQL and return */
KeLowerIrql(OldIrql);
return Status;
}
