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Date:      Mon, 06 Dec 1999 16:21:03 -0700
From:      Warner Losh <imp@village.org>
To:        Mike Smith <msmith@FreeBSD.ORG>
Cc:        mjacob@feral.com, hackers@FreeBSD.ORG
Subject:   Re: tty level buffer overflows 
Message-ID:  <199912062321.QAA37653@harmony.village.org>
In-Reply-To: Your message of "Sun, 05 Dec 1999 20:41:31 PST." <199912060441.UAA00805@mass.cdrom.com> 
References:  <199912060441.UAA00805@mass.cdrom.com>  

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In message <199912060441.UAA00805@mass.cdrom.com> Mike Smith writes:
: Yup. Ignore the "problem in the application" part, as that predicates 
: that the kernel and driver are working properly, which doesn't seem to be 
: the case.  The problem here is that the buffer between the top side of 
: the driver and the application isn't being drained fast enough.  It would 
: be educational to know what the app is sleeping on when these messages 
: are emitted; just dropping to ddb and using 'ps' would probably be 
: enough.  There has to be some reason that the process is either not being 
: woken when data arrives, or is being held up somewhere else for long 
: enough that the clist overflows.  
: 
: Does the problem still manifest with the recent scheduler changes?  
: Perhaps the comms processes are being unfairly scheduled against for some 
: reason?

We're seeing it with our ppp link, which uses the kernel level ppp
code.  Since it doesn't happen for me often, it is hard to diagnose.

Warner


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