kern/51982: sio1: interrupt-level buffer overflows
ianf at za.uu.net
Fri May 9 00:30:17 PDT 2003
The following reply was made to PR kern/51982; it has been noted by GNATS.
From: "Ian Freislich" <ianf at za.uu.net>
To: Bruce Evans <bde at zeta.org.au>
Cc: FreeBSD-gnats-submit at freebsd.org, freebsd-bugs at freebsd.org
Subject: Re: kern/51982: sio1: interrupt-level buffer overflows
Date: Fri, 09 May 2003 09:29:53 +0200
Bruce Evans wrote:
> On Mon, 5 May 2003, Ian Freislich wrote:
> > >Description:
> > Transferring data at "high" speed 115200bps over the serial
> > line (even though the actual incoming line stream is about
> > 37000bps according to the modem LCD panel) results in the
> > following messages on the console at a rate of about 1 log
> > line every 10 to 15 seconds.
> > These buffer overruns have gradually become more frequent
> > from about 3 lines and 24 overruns a day around September
> > 2002 (when I started running Current - 4.x does not suffer
> > from this) to the current flurry.
> -current has excessive interrupt latency caused by Giant locking almost
> Try changing this line in sio.c:
> cp4ticks = speed / 10 / hz * 4;
> to something like:
> cp4ticks = speed / 10 / hz * 40;
Thanks. Making this change seems to have fixed the problem. Will
this be committed or do I need to maintain this privately until the
larger interrupt latency problem is fixed?
> Transient interrupt latency problems are supposed to be made harmless
> by using rts flow control. There is a PR (maybe from you?) about rts
> flow control apparently not working for one modem.
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