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