I experimented with my modem connected to /dev/ttyS3 (COM4)
and got some strange repeatable behavior of the kernel:
vvv:~# echo at >/dev/ttyS3 &
[1] 288
vvv:~# cat /dev/ttyS3 &
[2] 289
vvv:~# cat /dev/cua3
Warning: dev (04:43) tty->count(1) != #fd's(2) in release_dev
vvv:~# cat /dev/cua3
Warning: dev (04:43) tty->count(1) != #fd's(2) in release_dev
vvv:~# cat /dev/cua3
Warning: dev (04:43) tty->count(1) != #fd's(2) in release_dev
vvv:~#
The command `echo at >/dev/ttyS3' does not exit
(that's why I've run it in a background); then
I've run `cat /dev/ttyS3' and finally, `cat /dev/cua3'.
Then I pressed Ctrl+C, and got the warning.
This can be repeated any number of times.
I do not want to say that these commands are useful, ---
just wanted to let you know about this behavior.
With best regards,
Vladimir.