162 lines
3.7 KiB
C
162 lines
3.7 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 fsctrl.c on the peek request.
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1) Each time peek is called it calls RxShouldRequestBeThrottled.
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When the result is true, the wrapper 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 the result is 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 the wrapper calls RxInitiateOrContinueThrottling.
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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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RxTerminateThrottling is called.
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Revision History:
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ColinWatson [ColinW] 24-Dec-1990 Created
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Joe Linn [JoeLinn] 10-Oct-1996 Lifted from rdr1 and massaged for rdr2
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--*/
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#include "precomp.h"
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#pragma hdrstop
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#ifdef ALLOC_PRAGMA
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//#pragma alloc_text(PAGE3FILE, RxBackOff) spinlock
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//#pragma alloc_text(PAGE3FILE, RxBackPackFailure) spinlock
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#endif
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BOOLEAN
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RxShouldRequestBeThrottled (
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IN PTHROTTLING_STATE 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,SavedThrottlingTime;
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BOOLEAN result;
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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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( pBP->MaximumDelay == 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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InterlockedIncrement(&pBP->NumberOfQueries);
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SavedThrottlingTime.QuadPart = 0;
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RxAcquireSerializationMutex();
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SavedThrottlingTime.QuadPart = pBP->NextTime.QuadPart;
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RxReleaseSerializationMutex();
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result = (CurrentTime.QuadPart < SavedThrottlingTime.QuadPart);
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RxLog(("shouldthrttle=%x (%x)\n",result,pBP));
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return(result);
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}
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VOID
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RxInitiateOrContinueThrottling (
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IN PTHROTTLING_STATE 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,NextTime;
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KeQuerySystemTime(&CurrentTime);
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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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InterlockedIncrement(&pBP->CurrentIncrement);
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}
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// NextTime = CurrentTime + (Interval * CurrentIncrement )
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NextTime.QuadPart = CurrentTime.QuadPart +
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(pBP->Increment.QuadPart * pBP->CurrentIncrement);
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RxAcquireSerializationMutex();
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pBP->NextTime.QuadPart = NextTime.QuadPart;
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RxReleaseSerializationMutex();
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}
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