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From: jeh@cmkrnl.com (Jamie Hanrahan)
Newsgroups: comp.os.ms-windows.programmer.nt.kernel-mode
Subject: Re: KeInsertQueueDpc bug on SMP systems?
Message-ID: <1998Jan16.154525.8420@cmkrnl>
Date: 16 Jan 98 15:45:25 PST
References: <69lhm3$q2r$1@decius.ultra.net> <69od14$ptg@news.microsoft.com> <34cfd06e.183398828@news.alt.net>
Organization: Kernel Mode Systems, San Diego, CA
Lines: 24

In article <34cfd06e.183398828@news.alt.net>, tony@ercolano.com (Anthony V. Ercolano) writes:
> Paul, I have a proposal for a doc change.
> 
> Right now it says:
> 
> "If the specified DPC object is already in the DPC queue, no operation
> is performed except to return FALSE. Otherwise, the DPC object is
> inserted in the DPC queue and a software interrupt is requested at
> IRQL DISPATCH_LEVEL on the current processor."
> 
> after "return FALSE", please insert: "Or we may (if you're unlucky)
> totally screw up kernel maintained data structures, and bugcheck
> shortly thereafter.  

Not quite.  If it's already on the queue, there isn't a problem.  
The problem shows up if it ISN'T on the queue and you try to 
insert it from more than one CPU at very close to the same time. 

	--- Jamie Hanrahan, Kernel Mode Systems, San Diego CA
        Internet: jeh@cmkrnl.com (JH645)  CompuServe: 74140,2055  
drivers, internals, networks, applications, and training for VMS and Windows NT
NT driver FAQ, links, and other information:  http://www.cmkrnl.com/

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