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/*++
Copyright (c) Microsoft Corporation. All rights reserved
Abstract:
Stream Edit Callout Driver Sample.
This file implements Light Weight queues using Worker Item routines.
Environment:
Kernel mode
--*/
#define POOL_ZERO_DOWN_LEVEL_SUPPORT
#include "LwQueue.h"
IO_WORKITEM_ROUTINE LwWorker;
NTSTATUS
LwInitializeQueue(
_In_ PVOID IoObject,
_Out_ PLW_QUEUE Queue,
_In_ PIO_WORKITEM_ROUTINE WorkerRoutine
)
/*
Initializes Light Weight Queue data structures!
*/
{
RtlZeroMemory(Queue, sizeof(Queue[0]));
Queue->Head = &Queue->Dummy;
Queue->Tail = &Queue->Dummy;
Queue->WorkerScheduled = FALSE;
Queue->WorkerRoutine = WorkerRoutine;
Queue->IoObject = IoObject;
KeInitializeSpinLock(&Queue->Lock);
Queue->WorkItem =
ExAllocatePool2(
POOL_FLAG_NON_PAGED, IoSizeofWorkItem(), STMEDIT_TAG_LQWI);
if (Queue->WorkItem == NULL)
{
return STATUS_INSUFFICIENT_RESOURCES;
}
IoInitializeWorkItem(IoObject, Queue->WorkItem);
Queue->Initialized = TRUE;
return STATUS_SUCCESS;
}
VOID
LwUninitializeQueue(
_Inout_ PLW_QUEUE Queue
)
/*
De-Initializes the Light Weight Queue!
*/
{
if (Queue->Initialized == FALSE)
{
return;
}
Queue->Initialized = FALSE;
IoUninitializeWorkItem(Queue->WorkItem);
ExFreePoolWithTag(Queue->WorkItem, STMEDIT_TAG_LQWI);
Queue->WorkItem = NULL;
}
__drv_functionClass(IO_WORKITEM_ROUTINE)
__drv_requiresIRQL(PASSIVE_LEVEL)
__drv_sameIRQL
VOID
LwWorker(
_In_ PDEVICE_OBJECT DeviceObject,
_In_opt_ PVOID Context
)
/*
Queue processing workitem routine.
Drains the task queue and invokes OOB Workitem to process the tasks.
*/
{
PLW_ENTRY Entry;
PLW_QUEUE Queue = (PLW_QUEUE)Context;
UNREFERENCED_PARAMETER(DeviceObject);
NT_ASSERT(Queue != NULL);
Entry = LwDequeueAll(Queue);
//
// Why were we scheduled if there are no entries?
//
NT_ASSERT(Entry != NULL);
while (Entry != NULL)
{
//
// Invoke the caller's worker routine.
//
Queue->WorkerRoutine(DeviceObject, Entry);
//
// Check if any other entries were added while we were
// working.
//
Entry = LwDequeueAll(Queue);
}
}
VOID
LwEnqueue(
_In_ PLW_QUEUE Queue,
_In_ PLW_ENTRY Entry
)
/*
Queue a task into the task queue.
*/
{
KLOCK_QUEUE_HANDLE LockHandle;
NT_ASSERT(Entry != NULL);
NT_ASSERT(Queue != NULL);
KeAcquireInStackQueuedSpinLock(&Queue->Lock, &LockHandle);
Entry->Next = NULL;
Queue->Tail->Next = Entry;
Queue->Tail = Entry;
if (!Queue->WorkerScheduled)
{
Queue->WorkerScheduled = TRUE;
IoQueueWorkItem(
Queue->WorkItem, LwWorker, DelayedWorkQueue, Queue);
}
KeReleaseInStackQueuedSpinLock(&LockHandle);
}
PLW_ENTRY
LwDequeueAll(
_In_ PLW_QUEUE Queue
)
{
KLOCK_QUEUE_HANDLE LockHandle;
PLW_ENTRY Entry = NULL;
KeAcquireInStackQueuedSpinLock(&Queue->Lock, &LockHandle);
NT_ASSERT(Queue->Head == &Queue->Dummy);
//
// Snap and return the entire queue contents.
//
Entry = Queue->Head->Next;
Queue->Head->Next = NULL;
Queue->Tail = Queue->Head;
if (Entry == NULL)
{
Queue->WorkerScheduled = FALSE;
}
KeReleaseInStackQueuedSpinLock(&LockHandle);
return Entry;
}
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