PKTHREAD
FASTCALL
KiSelectNextThread(IN PKPRCB Prcb)
{
PKTHREAD Thread;
/* Select a ready thread */
Thread = KiSelectReadyThread(0, Prcb);
if (!Thread)
{
/* Didn't find any, get the current idle thread */
Thread = Prcb->IdleThread;
/* Enable idle scheduling */
InterlockedOrSetMember(&KiIdleSummary, Prcb->SetMember);
Prcb->IdleSchedule = TRUE;
/* FIXME: SMT support */
ASSERTMSG("SMP: Not yet implemented\n", FALSE);
}
/* Sanity checks and return the thread */
ASSERT(Thread != NULL);
ASSERT((Thread->BasePriority == 0) || (Thread->Priority != 0));
return Thread;
}
VOID
NTAPI
KiAdjustQuantumThread(IN PKTHREAD Thread)
{
PKPRCB Prcb = KeGetCurrentPrcb();
PKTHREAD NextThread;
/* Acquire thread and PRCB lock */
KiAcquireThreadLock(Thread);
KiAcquirePrcbLock(Prcb);
/* Don't adjust for RT threads */
if ((Thread->Priority < LOW_REALTIME_PRIORITY) &&
(Thread->BasePriority < (LOW_REALTIME_PRIORITY - 2)))
{
/* Decrease Quantum by one and see if we've ran out */
if (--Thread->Quantum <= 0)
{
/* Return quantum */
Thread->Quantum = Thread->QuantumReset;
/* Calculate new Priority */
Thread->Priority = KiComputeNewPriority(Thread, 1);
/* Check if there's no next thread scheduled */
if (!Prcb->NextThread)
{
/* Select a ready thread and check if we found one */
NextThread = KiSelectReadyThread(Thread->Priority, Prcb);
if (NextThread)
{
/* Set it on standby and switch to it */
NextThread->State = Standby;
Prcb->NextThread = NextThread;
}
}
else
{
/* This thread can be preempted again */
Thread->Preempted = FALSE;
}
}
}
/* Release locks */
KiReleasePrcbLock(Prcb);
KiReleaseThreadLock(Thread);
KiExitDispatcher(Thread->WaitIrql);
}
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;
}
VOID
FASTCALL
KiSetPriorityThread(IN PKTHREAD Thread,
IN KPRIORITY Priority)
{
PKPRCB Prcb;
ULONG Processor;
BOOLEAN RequestInterrupt = FALSE;
KPRIORITY OldPriority;
PKTHREAD NewThread;
ASSERT((Priority >= 0) && (Priority <= HIGH_PRIORITY));
/* Check if priority changed */
if (Thread->Priority != Priority)
{
/* Loop priority setting in case we need to start over */
for (;;)
{
/* Choose action based on thread's state */
if (Thread->State == Ready)
{
/* Make sure we're not on the ready queue */
if (!Thread->ProcessReadyQueue)
{
/* Get the PRCB for the thread and lock it */
Processor = Thread->NextProcessor;
Prcb = KiProcessorBlock[Processor];
KiAcquirePrcbLock(Prcb);
/* Make sure the thread is still ready and on this CPU */
if ((Thread->State == Ready) &&
(Thread->NextProcessor == Prcb->Number))
{
/* Sanity check */
ASSERT((Prcb->ReadySummary &
PRIORITY_MASK(Thread->Priority)));
/* Remove it from the current queue */
if (RemoveEntryList(&Thread->WaitListEntry))
{
/* Update the ready summary */
Prcb->ReadySummary ^= PRIORITY_MASK(Thread->
Priority);
}
/* Update priority */
Thread->Priority = (SCHAR)Priority;
/* Re-insert it at its current priority */
KiInsertDeferredReadyList(Thread);
/* Release the PRCB Lock */
KiReleasePrcbLock(Prcb);
}
else
{
/* Release the lock and loop again */
KiReleasePrcbLock(Prcb);
continue;
}
}
else
{
/* It's already on the ready queue, just update priority */
Thread->Priority = (SCHAR)Priority;
}
}
else if (Thread->State == Standby)
{
/* Get the PRCB for the thread and lock it */
Processor = Thread->NextProcessor;
Prcb = KiProcessorBlock[Processor];
KiAcquirePrcbLock(Prcb);
/* Check if we're still the next thread to run */
if (Thread == Prcb->NextThread)
{
/* Get the old priority and update ours */
OldPriority = Thread->Priority;
Thread->Priority = (SCHAR)Priority;
/* Check if there was a change */
if (Priority < OldPriority)
{
/* Find a new thread */
NewThread = KiSelectReadyThread(Priority + 1, Prcb);
if (NewThread)
{
/* Found a new one, set it on standby */
NewThread->State = Standby;
Prcb->NextThread = NewThread;
/* Dispatch our thread */
KiInsertDeferredReadyList(Thread);
}
}
/* Release the PRCB lock */
KiReleasePrcbLock(Prcb);
}
else
{
/* Release the lock and try again */
KiReleasePrcbLock(Prcb);
continue;
}
}
else if (Thread->State == Running)
{
/* Get the PRCB for the thread and lock it */
Processor = Thread->NextProcessor;
Prcb = KiProcessorBlock[Processor];
KiAcquirePrcbLock(Prcb);
/* Check if we're still the current thread running */
if (Thread == Prcb->CurrentThread)
{
/* Get the old priority and update ours */
OldPriority = Thread->Priority;
Thread->Priority = (SCHAR)Priority;
/* Check if there was a change and there's no new thread */
if ((Priority < OldPriority) && !(Prcb->NextThread))
{
/* Find a new thread */
NewThread = KiSelectReadyThread(Priority + 1, Prcb);
if (NewThread)
{
/* Found a new one, set it on standby */
NewThread->State = Standby;
Prcb->NextThread = NewThread;
/* Request an interrupt */
RequestInterrupt = TRUE;
}
}
/* Release the lock and check if we need an interrupt */
KiReleasePrcbLock(Prcb);
if (RequestInterrupt)
{
/* Check if we're running on another CPU */
if (KeGetCurrentProcessorNumber() != Processor)
{
/* We are, send an IPI */
KiIpiSend(AFFINITY_MASK(Processor), IPI_DPC);
}
}
}
else
{
/* Thread changed, release lock and restart */
KiReleasePrcbLock(Prcb);
continue;
}
}
else if (Thread->State == DeferredReady)
{
/* FIXME: TODO */
DPRINT1("Deferred state not yet supported\n");
ASSERT(FALSE);
}
else
{
/* Any other state, just change priority */
Thread->Priority = (SCHAR)Priority;
}
/* If we got here, then thread state was consistent, so bail out */
break;
}
}
}
LONG_PTR
FASTCALL
KiSwapThread(IN PKTHREAD CurrentThread,
IN PKPRCB Prcb)
{
BOOLEAN ApcState = FALSE;
KIRQL WaitIrql;
LONG_PTR WaitStatus;
PKTHREAD NextThread;
ASSERT(KeGetCurrentIrql() >= DISPATCH_LEVEL);
/* Acquire the PRCB lock */
KiAcquirePrcbLock(Prcb);
/* Get the next thread */
NextThread = Prcb->NextThread;
if (NextThread)
{
/* Already got a thread, set it up */
Prcb->NextThread = NULL;
Prcb->CurrentThread = NextThread;
NextThread->State = Running;
}
else
{
/* Try to find a ready thread */
NextThread = KiSelectReadyThread(0, Prcb);
if (NextThread)
{
/* Switch to it */
Prcb->CurrentThread = NextThread;
NextThread->State = Running;
}
else
{
/* Set the idle summary */
InterlockedOrSetMember(&KiIdleSummary, Prcb->SetMember);
/* Schedule the idle thread */
NextThread = Prcb->IdleThread;
Prcb->CurrentThread = NextThread;
NextThread->State = Running;
}
}
/* Sanity check and release the PRCB */
ASSERT(CurrentThread != Prcb->IdleThread);
KiReleasePrcbLock(Prcb);
/* Save the wait IRQL */
WaitIrql = CurrentThread->WaitIrql;
/* Swap contexts */
ApcState = KiSwapContext(WaitIrql, CurrentThread);
/* Get the wait status */
WaitStatus = CurrentThread->WaitStatus;
/* Check if we need to deliver APCs */
if (ApcState)
{
/* Lower to APC_LEVEL */
KeLowerIrql(APC_LEVEL);
/* Deliver APCs */
KiDeliverApc(KernelMode, NULL, NULL);
ASSERT(WaitIrql == 0);
}
/* Lower IRQL back to what it was and return the wait status */
KeLowerIrql(WaitIrql);
return WaitStatus;
}
NTSTATUS
NtYieldExecution (
VOID
)
/*++
Routine Description:
This function yields execution to any ready thread for up to one
quantum.
Arguments:
None.
Return Value:
None.
--*/
{
KIRQL OldIrql;
PKTHREAD NewThread;
PRKPRCB Prcb;
NTSTATUS Status;
PKTHREAD Thread;
//
// If no other threads are ready, then return immediately. Otherwise,
// attempt to yield execution.
//
// N.B. The test for ready threads is made outside any synchonization.
// Since this code cannot be perfectly synchronized under any
// conditions the lack of synchronization is of no consequence.
//
if (KiGetCurrentReadySummary() == 0) {
return STATUS_NO_YIELD_PERFORMED;
} else {
Status = STATUS_NO_YIELD_PERFORMED;
Thread = KeGetCurrentThread();
OldIrql = KeRaiseIrqlToSynchLevel();
Prcb = KeGetCurrentPrcb();
if (Prcb->ReadySummary != 0) {
//
// Acquire the thread lock and the PRCB lock.
//
// If a thread has not already been selected for execution, then
// attempt to select another thread for execution.
//
KiAcquireThreadLock(Thread);
KiAcquirePrcbLock(Prcb);
if (Prcb->NextThread == NULL) {
Prcb->NextThread = KiSelectReadyThread(1, Prcb);
}
//
// If a new thread has been selected for execution, then switch
// immediately to the selected thread.
//
if ((NewThread = Prcb->NextThread) != NULL) {
Thread->Quantum = Thread->QuantumReset;
//
// Compute the new thread priority.
//
// N.B. The new priority will never be greater than the previous
// priority.
//
Thread->Priority = KiComputeNewPriority(Thread, 1);
//
// Release the thread lock, set swap busy for the old thread,
// set the next thread to NULL, set the current thread to the
// new thread, set the new thread state to running, set the
// wait reason, queue the old running thread, and release the
// PRCB lock, and swp context to the new thread.
//
KiReleaseThreadLock(Thread);
KiSetContextSwapBusy(Thread);
Prcb->NextThread = NULL;
Prcb->CurrentThread = NewThread;
NewThread->State = Running;
Thread->WaitReason = WrYieldExecution;
KxQueueReadyThread(Thread, Prcb);
Thread->WaitIrql = APC_LEVEL;
ASSERT(OldIrql <= DISPATCH_LEVEL);
KiSwapContext(Thread, NewThread);
Status = STATUS_SUCCESS;
} else {
KiReleasePrcbLock(Prcb);
KiReleaseThreadLock(Thread);
}
}
//
// Lower IRQL to its previous level and return.
//
KeLowerIrql(OldIrql);
return Status;
}
}