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SubjectRe: Hang on 2.2.17 - serial/tty related?
From
   From: Russell King <rmk@arm.linux.org.uk>
Date: Wed, 20 Sep 2000 22:45:59 +0100 (BST)

I just experianced a complete hang of one of my systems here after using
the serial port a lot (ie, open, read/write, close). I was using minicom,
and I started to notice that each time I quit minicom, it would not exit.

ps alx revealed that it was waiting in tty_wait_until_sent, yet the serial
port was not doing anything at all (I've got a couple of LEDs on the Tx
and Rx lines). However, the port was in xon/xoff mode, but it seemed to
be capable of transmitting immediately prior (note that at this time, the
remote end had no capability to send an xon character to stop the
transmission).

Can you define TTY_DEBUG_WAIT_UNTIL_SENT in tty_ioctl.c and
RS_DEBUG_WAIT_UNTIL_SENT in serial.c and send me the results?

Also, which version of the serial driver are you using? The stock
2.2.17 or the one in serial.sourceforge.net?

When the actual crash happened, I changed the baud rate on the target
system, and just changed the local baud rate to 115200. I then hit the
enter key and that was game over. No response on network, nor X. The
machine was completely and utterly dead to the point of requiring a
hardware reset.

Hmm... my guess is that it may not be the baud rate changing, but the
fact that the stty results in tty_wait_util_sent, and something is
getting screwed up at that point. So if you could try to replicate the
problem with the debugging statements defined, and then send the kernel
log messages, that would be most useful.

Thanks!!

- Ted
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