Created attachment 525036 [details]
proposed patch

Description of problem:
A customer could not pass more than a single character to the login process.
This situation was so similar to BZ681167.
  https://bugzilla.redhat.com/show_bug.cgi?id=681167
The kernel parameter includes "console=tty0 console=ttyS0,9600", and it doesn't include "rhgb quiet".

First, we tried the following upstream fixes, but this problem was not fixed.

  commit 89096d735f78fab300248962030d6554f9894011
  commit 74ed81c79c37c852d9011159efe1ddbdecb1fb65
  commit bb3be6b60f6f0b8f8cea67b7817210b7e7164043

I checked if ply_terminal_lock() and ply_terminal_unlock() are called for what terminal with debug package. And, I found that ply_terminal_unlock() was not called clearly for /dev/ttyS0.

ply_terminal_lock() and ply_terminal_unlock() are called from ply_terminal_open() and ply_terminal_close().

 ply_terminal_open()
 ...
  -> ply_terminal_unlock, lock

 ply_terminal_close()
 ...
  -> ply_terminal_unlock()

The details plugin has add_text_display() and remove_text_display() functions and those are called when the display with a terminal is added or removed from the linked list. I noticed that add_text_display() calls ply_terminal_open().
But, remove_text_display() doesn't call ply_terminal_close(). As a result, it seems that the terminal keeps to be locked.

I created a proposed patch and confirmed it was fixed.
I will attach the patch.

Version-Release number of selected component (if applicable):
Red Hat Enterprise Linux 6.1

How reproducible:
Always

Steps to Reproduce:
1. got the machine with serial console
2. boot the kernel parameter with "console=tty0 console=ttyS0,9600", and delete "rhgb quiet".
3. boot the machine, and try to login from serial console.
  
Actual results:
cannot login from serial console

Expected results:
can login from serial console