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Date: Thu, 13 Jan 2022 09:39:23 -0500
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Subject: Re: [PATCH] fhandler_pipe: add sanity limit to handle loops
To: cygwin AT cygwin DOT com
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From: Ken Brown <kbrown AT cornell DOT edu>
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On 1/13/2022 5:56 AM, Takashi Yano wrote:
> Ken Brown wrote:
>> 2. You can use the ReturnLength parameter of NtQueryInformationProcess to see
>> how big a buffer is needed.  This might be more efficient than repeatedly
>> doubling the buffer size.
> 
> Even if ReturnLength is used, the first NtQueryInformationProcess()
> call and the second NtQueryInformationProcess() call will not be
> done in atomic, so retrying is still necessary. However, it may be
> more efficient as you mentioned.
> 
> The similar is true also for NtQuerySystemInformation().
> 
> Do you still think it is better to use ReturnLength rather than
> doubling the buffer?

I'm not sure.  I only mentioned it because I saw that that's what Process Hacker 
did, but still in a retry loop as you said.

I suspect it doesn't make a lot of difference in practice, since we call the 
function once and then cache the value.  Do whatever you think is best.

Thanks.

Ken

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