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389 lines
13 KiB
C
389 lines
13 KiB
C
/*
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* ReactOS Cancel-Safe Queue library
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* Copyright (c) 2004, Vizzini (vizzini@plasmic.com)
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* Licensed under the GNU GPL for the ReactOS project
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*
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* This file implements the ReactOS CSQ library. For background and overview
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* information on these routines, read csq.h. For the authoritative reference
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* to using these routines, see the current DDK (IoCsqXXX and CsqXxx callbacks).
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*
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* There are a couple of subtle races that this library is designed to avoid.
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* Please read the code (particularly IoCsqInsertIrpEx and IoCsqRemoveIrp) for
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* some details.
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*
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* In general, we try here to avoid the race between these queue/dequeue
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* interfaces and our own cancel routine. This library supplies a cancel
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* routine that is used in all IRPs that are queued to it. The major race
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* conditions surround the proper handling of in-between cases, such as in-progress
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* queue and de-queue operations.
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*
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* When you're thinking about these operations, keep in mind that three or four
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* processors can have queue and dequeue operations in progress simultaneously,
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* and a user thread may cancel any IRP at any time. Also, these operations don't
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* all happen at DISPATCH_LEVEL all of the time, so thread switching on a single
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* processor can create races too.
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*/
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/* $Id$ */
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#include <ntdef.h>
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#undef DECLSPEC_IMPORT
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#define DECLSPEC_IMPORT
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#include <ntifs.h>
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static VOID NTAPI IopCsqCancelRoutine(PDEVICE_OBJECT DeviceObject,
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PIRP Irp)
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/*
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* FUNCTION: Cancel routine that is installed on any IRP that this library manages
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* ARGUMENTS:
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* [Called back by the system]
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* NOTES:
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* - We assume that Irp->Tail.Overlay.DriverContext[3] has either a IO_CSQ
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* or an IO_CSQ_IRP_CONTEXT in it, but we have to figure out which it is
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* - By the time this routine executes, the I/O Manager has already cleared
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* the cancel routine pointer in the IRP, so it will only be canceled once
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* - Because of this, we're guaranteed that Irp is valid the whole time
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* - Don't forget to release the cancel spinlock ASAP --> #1 hot lock in the
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* system
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* - May be called at high IRQL
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*/
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{
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PIO_CSQ Csq;
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KIRQL Irql;
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/* First things first: */
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IoReleaseCancelSpinLock(Irp->CancelIrql);
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/* We could either get a context or just a csq */
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Csq = (PIO_CSQ)Irp->Tail.Overlay.DriverContext[3];
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if(Csq->Type == IO_TYPE_CSQ_IRP_CONTEXT)
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{
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PIO_CSQ_IRP_CONTEXT Context = (PIO_CSQ_IRP_CONTEXT)Csq;
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Csq = Context->Csq;
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/* clean up context while we're here */
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Context->Irp = NULL;
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}
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/* Now that we have our CSQ, complete the IRP */
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Csq->CsqAcquireLock(Csq, &Irql);
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{
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Csq->CsqRemoveIrp(Csq, Irp);
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Csq->CsqCompleteCanceledIrp(Csq, Irp);
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}
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Csq->CsqReleaseLock(Csq, Irql);
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}
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NTSTATUS NTAPI IoCsqInitialize(PIO_CSQ Csq,
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PIO_CSQ_INSERT_IRP CsqInsertIrp,
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PIO_CSQ_REMOVE_IRP CsqRemoveIrp,
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PIO_CSQ_PEEK_NEXT_IRP CsqPeekNextIrp,
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PIO_CSQ_ACQUIRE_LOCK CsqAcquireLock,
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PIO_CSQ_RELEASE_LOCK CsqReleaseLock,
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PIO_CSQ_COMPLETE_CANCELED_IRP CsqCompleteCanceledIrp)
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/*
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* FUNCTION: Set up a CSQ struct to initialize the queue
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* ARGUMENTS:
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* Csq: Caller-allocated non-paged space for our IO_CSQ to be initialized
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* CsqInsertIrp: Insert routine
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* CsqRemoveIrp: Remove routine
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* CsqPeekNextIrp: Routine to paeek at the next IRP in queue
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* CsqAcquireLock: Acquire the queue's lock
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* CsqReleaseLock: Release the queue's lock
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* CsqCompleteCanceledIrp: Routine to complete IRPs when they are canceled
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* RETURNS:
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* - STATUS_SUCCESS in all cases
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* NOTES:
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* - Csq must be non-paged, as the queue is manipulated with a held spinlock
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*/
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{
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Csq->Type = IO_TYPE_CSQ;
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Csq->CsqInsertIrp = CsqInsertIrp;
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Csq->CsqRemoveIrp = CsqRemoveIrp;
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Csq->CsqPeekNextIrp = CsqPeekNextIrp;
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Csq->CsqAcquireLock = CsqAcquireLock;
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Csq->CsqReleaseLock = CsqReleaseLock;
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Csq->CsqCompleteCanceledIrp = CsqCompleteCanceledIrp;
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Csq->ReservePointer = NULL;
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return STATUS_SUCCESS;
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}
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NTSTATUS NTAPI IoCsqInitializeEx(PIO_CSQ Csq,
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PIO_CSQ_INSERT_IRP_EX CsqInsertIrpEx,
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PIO_CSQ_REMOVE_IRP CsqRemoveIrp,
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PIO_CSQ_PEEK_NEXT_IRP CsqPeekNextIrp,
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PIO_CSQ_ACQUIRE_LOCK CsqAcquireLock,
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PIO_CSQ_RELEASE_LOCK CsqReleaseLock,
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PIO_CSQ_COMPLETE_CANCELED_IRP CsqCompleteCanceledIrp)
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/*
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* FUNCTION: Set up a CSQ struct to initialize the queue (extended version)
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* ARGUMENTS:
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* Csq: Caller-allocated non-paged space for our IO_CSQ to be initialized
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* CsqInsertIrpEx: Extended insert routine
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* CsqRemoveIrp: Remove routine
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* CsqPeekNextIrp: Routine to paeek at the next IRP in queue
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* CsqAcquireLock: Acquire the queue's lock
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* CsqReleaseLock: Release the queue's lock
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* CsqCompleteCanceledIrp: Routine to complete IRPs when they are canceled
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* RETURNS:
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* - STATUS_SUCCESS in all cases
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* NOTES:
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* - Csq must be non-paged, as the queue is manipulated with a held spinlock
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*/
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{
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Csq->Type = IO_TYPE_CSQ_EX;
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Csq->CsqInsertIrp = (PIO_CSQ_INSERT_IRP)CsqInsertIrpEx;
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Csq->CsqRemoveIrp = CsqRemoveIrp;
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Csq->CsqPeekNextIrp = CsqPeekNextIrp;
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Csq->CsqAcquireLock = CsqAcquireLock;
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Csq->CsqReleaseLock = CsqReleaseLock;
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Csq->CsqCompleteCanceledIrp = CsqCompleteCanceledIrp;
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Csq->ReservePointer = NULL;
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return STATUS_SUCCESS;
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}
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VOID NTAPI IoCsqInsertIrp(PIO_CSQ Csq,
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PIRP Irp,
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PIO_CSQ_IRP_CONTEXT Context)
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/*
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* FUNCTION: Insert an IRP into the CSQ
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* ARGUMENTS:
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* Csq: Pointer to the initialized CSQ
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* Irp: Pointer to the IRP to queue
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* Context: Context record to track the IRP while queued
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* NOTES:
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* - Just passes through to IoCsqInsertIrpEx, with no InsertContext
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*/
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{
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IoCsqInsertIrpEx(Csq, Irp, Context, 0);
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}
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NTSTATUS NTAPI IoCsqInsertIrpEx(PIO_CSQ Csq,
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PIRP Irp,
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PIO_CSQ_IRP_CONTEXT Context,
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PVOID InsertContext)
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/*
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* FUNCTION: Insert an IRP into the CSQ, with additional tracking context
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* ARGUMENTS:
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* Csq: Pointer to the initialized CSQ
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* Irp: Pointer to the IRP to queue
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* Context: Context record to track the IRP while queued
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* InsertContext: additional data that is passed through to CsqInsertIrpEx
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* NOTES:
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* - Passes the additional context through to the driver-supplied callback,
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* which can be used with more sophistocated queues
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* - Marks the IRP pending in all cases
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* - Guaranteed to not queue a canceled IRP
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* - This is complicated logic, and is patterend after the Microsoft library.
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* I'm sure I have gotten the details wrong on a fine point or two, but
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* basically this works with the MS-supplied samples.
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*/
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{
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NTSTATUS Retval = STATUS_SUCCESS;
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KIRQL Irql;
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Csq->CsqAcquireLock(Csq, &Irql);
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do
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{
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/* mark all irps pending -- says so in the cancel sample */
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IoMarkIrpPending(Irp);
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/* set up the context if we have one */
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if(Context)
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{
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Context->Type = IO_TYPE_CSQ_IRP_CONTEXT;
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Context->Irp = Irp;
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Context->Csq = Csq;
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Irp->Tail.Overlay.DriverContext[3] = Context;
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}
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else
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Irp->Tail.Overlay.DriverContext[3] = Csq;
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/*
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* NOTE! This is very sensitive to order. If you set the cancel routine
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* *before* you queue the IRP, our cancel routine will get called back for
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* an IRP that isn't in its queue.
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*
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* There are three possibilities:
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* 1) We get an IRP, we queue it, and it is valid the whole way
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* 2) We get an IRP, and the IO manager cancels it before we're done here
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* 3) We get an IRP, queue it, and the IO manager cancels it.
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*
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* #2 is is a booger.
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*
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* When the IO manger receives a request to cancel an IRP, it sets the cancel
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* bit in the IRP's control byte to TRUE. Then, it looks to see if a cancel
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* routine is set. If it isn't, the IO manager just returns to the caller.
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* If there *is* a routine, it gets called.
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*
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* If we test for cancel first and then set the cancel routine, there is a spot
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* between test and set that the IO manager can cancel us without our knowledge,
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* so we miss a cancel request. That is bad.
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*
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* If we set a routine first and then test for cancel, we race with our completion
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* routine: We set the routine, the IO Manager sets cancel, we test cancel and find
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* it is TRUE. Meanwhile the IO manager has called our cancel routine already, so
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* we can't complete the IRP because it'll rip it out from under the cancel routine.
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*
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* The IO manager does us a favor though: it nulls out the cancel routine in the IRP
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* before calling it. Therefore, if we test to see if the cancel routine is NULL
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* (after we have just set it), that means our own cancel routine is already working
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* on the IRP, and we can just return quietly. Otherwise, we have to de-queue the
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* IRP and cancel it ourselves.
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*
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* We have to go through all of this mess because this API guarantees that we will
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* never return having left a canceled IRP in the queue.
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*/
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/* Step 1: Queue the IRP */
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if(Csq->Type == IO_TYPE_CSQ)
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Csq->CsqInsertIrp(Csq, Irp);
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else
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{
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PIO_CSQ_INSERT_IRP_EX pCsqInsertIrpEx = (PIO_CSQ_INSERT_IRP_EX)Csq->CsqInsertIrp;
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Retval = pCsqInsertIrpEx(Csq, Irp, InsertContext);
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if(Retval != STATUS_SUCCESS)
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break;
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}
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/* Step 2: Set our cancel routine */
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(void)IoSetCancelRoutine(Irp, IopCsqCancelRoutine);
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/* Step 3: Deal with an IRP that is already canceled */
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if(!Irp->Cancel)
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break;
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/*
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* Since we're canceled, see if our cancel routine is already running
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* If this is NULL, the IO Manager has already called our cancel routine
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*/
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if(!IoSetCancelRoutine(Irp, NULL))
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break;
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/* OK, looks like we have to de-queue and complete this ourselves */
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Csq->CsqRemoveIrp(Csq, Irp);
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Csq->CsqCompleteCanceledIrp(Csq, Irp);
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if(Context)
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Context->Irp = NULL;
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}
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while(0);
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Csq->CsqReleaseLock(Csq, Irql);
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return Retval;
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}
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PIRP NTAPI IoCsqRemoveIrp(PIO_CSQ Csq,
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PIO_CSQ_IRP_CONTEXT Context)
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/*
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* FUNCTION: Remove anb IRP from the queue
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* ARGUMENTS:
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* Csq: Queue to remove the IRP from
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* Context: Context record containing the IRP to be dequeued
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* RETURNS:
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* - Pointer to an IRP if we found it
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* NOTES:
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* - Don't forget that we can be canceled any time up to the point
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* where we unset our cancel routine
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*/
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{
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KIRQL Irql;
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PIRP Irp = NULL;
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Csq->CsqAcquireLock(Csq, &Irql);
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do
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{
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/* It's possible that this IRP could have been canceled */
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Irp = Context->Irp;
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if(!Irp)
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break;
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/* Unset the cancel routine and see if it has already been canceled */
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if(!IoSetCancelRoutine(Irp, NULL))
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{
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/*
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* already gone, return NULL --> NOTE that we cannot touch this IRP *or* the context,
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* since the context is being simultaneously twiddled by the cancel routine
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*/
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Irp = NULL;
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break;
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}
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/* This IRP is valid and is ours. Dequeue it, fix it up, and return */
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Csq->CsqRemoveIrp(Csq, Irp);
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Context = (PIO_CSQ_IRP_CONTEXT)InterlockedExchangePointer(&Irp->Tail.Overlay.DriverContext[3], NULL);
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if(Context && Context->Type == IO_TYPE_CSQ_IRP_CONTEXT)
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Context->Irp = NULL;
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}
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while(0);
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Csq->CsqReleaseLock(Csq, Irql);
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return Irp;
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}
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PIRP NTAPI IoCsqRemoveNextIrp(PIO_CSQ Csq,
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PVOID PeekContext)
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/*
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* FUNCTION: IoCsqRemoveNextIrp - Removes the next IRP from the queue
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* ARGUMENTS:
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* Csq: Queue to remove the IRP from
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* PeekContext: Identifier of the IRP to be removed
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* RETURNS:
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* Pointer to the IRP that was removed, or NULL if one
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* could not be found
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* NOTES:
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* - This function is sensitive to yet another race condition.
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* The basic idea is that we have to return the first IRP that
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* we get that matches the PeekContext >that is not already canceled<.
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* Therefore, we have to do a trick similar to the one done in Insert
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* above.
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*/
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{
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KIRQL Irql;
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PIRP Irp = NULL;
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PIO_CSQ_IRP_CONTEXT Context;
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Csq->CsqAcquireLock(Csq, &Irql);
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while((Irp = Csq->CsqPeekNextIrp(Csq, Irp, PeekContext)))
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{
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/*
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* If the cancel routine is gone, we're already canceled,
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* and are spinning on the queue lock in our own cancel
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* routine. Move on to the next candidate. It'll get
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* removed by the cance routine.
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*/
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if(!IoSetCancelRoutine(Irp, NULL))
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continue;
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Csq->CsqRemoveIrp(Csq, Irp);
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/* Unset the context stuff and return */
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Context = (PIO_CSQ_IRP_CONTEXT)InterlockedExchangePointer(&Irp->Tail.Overlay.DriverContext[3], NULL);
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if(Context && Context->Type == IO_TYPE_CSQ_IRP_CONTEXT)
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Context->Irp = NULL;
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break;
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}
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Csq->CsqReleaseLock(Csq, Irql);
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return Irp;
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}
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