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Date:      Sat, 13 Nov 1999 00:46:56 -0800
From:      Mike Smith <mike@smith.net.au>
To:        Brian McGovern <bmcgover@cisco.com>
Cc:        hackers@freebsd.org, peter@freebsd.org
Subject:   Re: How does sio handle full clists? 
Message-ID:  <199911130846.AAA00574@dingo.cdrom.com>
In-Reply-To: Your message of "Tue, 09 Nov 1999 10:55:52 EST." <199911091555.KAA01889@bmcgover-pc.cisco.com> 

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> I've been digging around in the sio driver, trying to find out how it handles
> receive interrupts when the clists are full.
> 
> What I think I found (which is why I'm asking) is that if an RX interrupt
> occurs, and the clists are full and the driver can't offload all of the
> data from the UART, it disables the interrupts.

I don't believe it does this, no.

> I guess I'm looking for confirmation of this, and, if I'm way off, maybe a 
> quick explanatio of what _really_ happens. I'm looking at trying to reuse
> the behavior elsewhere, so I want a good understanding of the process before I
> get myself in to too much trouble.

You should expect to see the dreaded "tty-level buffer overflow" 
message, when the soft interrupt handler flushes the interrupt-level 
buffers into the tty subsystem.

-- 
\\ Give a man a fish, and you feed him for a day. \\  Mike Smith
\\ Tell him he should learn how to fish himself,  \\  msmith@freebsd.org
\\ and he'll hate you for a lifetime.             \\  msmith@cdrom.com




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