[minicom-Bugs][311345] CPU usage peaks to 100% when USB/Serial adapter is unplugged

Sat Jan 17 11:06:54 UTC 2009

Bugs item #311345, was opened at 2009-01-09 16:03
Status: Open
Priority: 3
Submitted By: Christopher Friedt (cfriedt-guest)
Assigned to: Nobody (None)
Summary: CPU usage peaks to 100% when USB/Serial adapter is unplugged 
Category: None
Group: None
Resolution: None

Initial Comment:
My system is running the Linux kernel 2.6.27, but this has happened for as long as I can remember. My colleague who uses a MacBook also observes this regularly. It is always reproducible.

The serial session is 115200 8 N 1 with no flow control, used simply to connect to the rs232 port of an SBC. 

The USB/Serial adaptor I'm using right now is based on the pl2303, but this has also happened with ftdi232 based adaptors.

It's hard to say that this is a problem in the Linux kernel, because it's also happening with Mac OS X, so the evidence suggests that it's a Minicom issue. 

My suggestions are

1) to listen to some kind of notification service from the kernel (inotify? dnotify?). Might work as a callback, eliminating the use of IPC/threads (?)

2) just periodically monitor the /dev node in a separate process, sending a SIGUSR1 to the parent process if the /dev node disappears. The parent process could catch the SIGUSR1 and close the session, informing the user of the error.

3) the same as 2, essentially, just using threads, a shared variable, mutexes... more complicated, but at least it stays in 1 process :)

Aside from that, I have never noticed a single problem in Minicom and have been using it for 8 years.

Keep up the great work!

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>Comment By: Adam Lackorzynski (al-guest)
Date: 2009-01-17 12:06

Message:
Hi,

I think this behaviour has been fixed in version 2.3.

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http://alioth.debian.org/tracker/?func=detail&atid=100031&aid=311345&group_id=30018