PUC Serial I/O problem - copy of gnats-filed bug report (as [SB QUAR: Sun Dec 13 10:50:06 2009] discussed previously)

[Jeremy Chadwick]

On Tue, Dec 15, 2009 at 09:57:59AM -0800, Marcel Moolenaar wrote:
> 
> On Dec 15, 2009, at 7:03 AM, Karl Denninger wrote:
> 
> > This is now marked fixed and it appears (after limited testing thus far)
> > that it indeed is.
> 
> The bug existed in 7 as well. It's not a regression introduced in 8.
> The reason why this didn't come up in the 7 time frame is that sio(4)
> was still the default. Jeremy has been an early adopter of uart(4)
> and if I'm not mistaken, he always loaded the driver(s) as modules.
> This, due to a "lucky" bug, avoided the problem for him.

Marcel,

Thanks for fixing the problem Karl's reported.  As I've stated in the
past, I appreciate your efforts and attentiveness to this sort of thing.
If there's any way I can repay you (Paypal donations, etc.), just let me
know and I'll do what I can.

With regards to my early testing of uart(4): I still use sio(4) on our
RELENG_7 systems, as I wasn't entirely sure if uart(4) was stable enough
or not (we use uart(4) reliably on our RELENG_8 systems though).  During
my brief testing of uart(4), it was most definitely compiled in to the
kernel(**).

Chances are I didn't uart(4) long enough (rather: use the serial port
enough!) to really give things a good whack.  Given that Karl's using
them for modems, I'd say his chance of seeing interrupt-related issues
are a lot higher than mine.

The serial ports on our systems are used solely for serial console
(115200bps, 8N1, CTS/RTS flow control), and with uart(4) worked OK for
the single-user-based steps of reinstalling world/mergemaster/etc..

I don't think puc(4) was in use, but I'm not 100% certain (I remember
including the device line in the kernel config, but I didn't see any
mention of anything attached to puc in dmesg; they all showed up as
being attached to acpi0).

(**): I tend to avoid kernel modules due to habit -- I guess because I'm
not sure if the module infrastructure is 100% reliable or not; scarce
are the number of times I've heard of someone encountering problems with
them, but old habits die hard...

-- 
| Jeremy Chadwick                                   jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |