163 lines
3.6 KiB
C
163 lines
3.6 KiB
C
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/*++
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Copyright (c) 1990 Microsoft Corporation
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Module Name:
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backpack.c
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Abstract:
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This module contains the package for pseudo polling. When a caller
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requests the same operation and gets the same error return the rdr
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must prevent flooding the network by backing off requests. Examples
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of when this is desirable are receiving 0 bytes on consequtive reads
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and consequtive fails on a file lock.
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If the caller is flooding the network, the rdr will return the 0 bytes
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for a pipe read or lock fail to the user until NextTime is reached.
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When NextTime is reached BackOff will indicate that the network should
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be used.
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Author:
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Colin Watson (colinw) 02-Jan-1991
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Notes:
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Typical usage would be demonstrated by rdr\npipe.c on the peek request.
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1) Each time peek is called it calls backoff.
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When backoff returns true, RdrNpPeek returns to the caller a response
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indicating there is no data at the other end of the pipe.
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When backoff returns false a request is made to the network.
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2) If the reply from the server to the peek in step 1 indicates that
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there is no data in the pipe then RdrNpPeek calls RdrBackPackFailure.
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3) Whenever there is data in the pipe or when this workstation may
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unblock the pipe (eg. the workstation writing to the pipe)
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RdrBackPackSuccess is called.
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Revision History:
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24-Dec-1990 ColinW
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Created
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--*/
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#include "precomp.h"
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#pragma hdrstop
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//
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// BackPackSpinLock is used to protect all Time entries in
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// the BACK_PACK structures from being accessed simultaneously.
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//
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KSPIN_LOCK BackPackSpinLock = {0};
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#ifdef ALLOC_PRAGMA
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#pragma alloc_text(PAGE3FILE, RdrBackOff)
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#pragma alloc_text(PAGE3FILE, RdrBackPackFailure)
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#endif
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BOOLEAN
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RdrBackOff (
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IN PBACK_PACK pBP
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)
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/*++
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Routine Description:
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This routine is called each time a request is made to find out if a the
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request should be sent to the network or a standard reply should be
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returned to the caller.
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Arguments:
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pBP - supplies back pack data for this request.
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Return Value:
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TRUE when caller should not access the network.
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--*/
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{
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LARGE_INTEGER CurrentTime;
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KIRQL OldIrql;
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DISCARDABLE_CODE(RdrFileDiscardableSection);
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// If the previous request worked then we should access the network.
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if ( pBP->CurrentIncrement == 0 ) {
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return FALSE;
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}
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// If the delay has expired then access the network.
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KeQuerySystemTime(&CurrentTime);
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ACQUIRE_SPIN_LOCK(&BackPackSpinLock, &OldIrql);
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if (CurrentTime.QuadPart < pBP->NextTime.QuadPart) {
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RELEASE_SPIN_LOCK(&BackPackSpinLock, OldIrql);
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return TRUE; // Not time to access the network yet.
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} else {
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RELEASE_SPIN_LOCK(&BackPackSpinLock, OldIrql);
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return FALSE;
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}
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}
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VOID
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RdrBackPackFailure (
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IN PBACK_PACK pBP
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)
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/*++
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Routine Description:
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This routine is called each time a request fails.
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Arguments:
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pBP - supplies back pack data for this request.
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Return Value:
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None.
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--*/
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{
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LARGE_INTEGER CurrentTime;
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KIRQL OldIrql;
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DISCARDABLE_CODE(RdrFileDiscardableSection);
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KeQuerySystemTime(&CurrentTime);
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ACQUIRE_SPIN_LOCK(&BackPackSpinLock, &OldIrql);
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if (pBP->CurrentIncrement < pBP->MaximumDelay ) {
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//
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// We have reached NextTime but not our maximum delay limit.
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//
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pBP->CurrentIncrement++;
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}
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// NextTime = CurrentTime + (Interval * CurrentIncrement )
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pBP->NextTime.QuadPart = CurrentTime.QuadPart + (pBP->Increment.QuadPart * pBP->CurrentIncrement);
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RELEASE_SPIN_LOCK(&BackPackSpinLock, OldIrql);
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}
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