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Flow-control weirdness

Aaron Burt aaron@osdl.org
Wed, 12 Mar 2003 11:56:39 -0800 (PST)

One of our programmers was diagnosing a problem with a RAID driver on
Linux via serial console when he ran in to an interesting problem:

The driver would dump a bunch of debug output, then stop in the middle.
He'd bang return and about 16 characters of additional output would print.
Each time he banged return, he'd get another li'l chunk of output.

He called me over and I disabled hardware flow-control on the console's
port on the terminal server (Computone RAS2000) and then did a ^Ecd/^Eco
to cycle the port and apply the change.  The rest of the output spooled
out, and I figured there was some sort of problem in the kernel's serial
console code with hardware flow-control.

To confirm the fix, I had him reproduce it again.  The problem recurred
exactly the same way, even with no flow control.

Put flow-control back, cycled the port again and the reset of the output
flowed out.

For now, I've told hom to cycle the port when this happens.

I'm running Conserver 7.2.1 installed via handrolled RPM on a heavily
doctored RH 7.1 system.

Any clues, O Oracles of Serial Niftiness?

Thanks in advance,