[Bug 78470] switching to current logged in user freezes gdm

[chantra]

Public bug reported:

Binary package hint: gdm

on feisty  with gdm 2.17.4-0ubuntu1 gdm freezes when user X is already logged, user X switch user and log in as user X again.
The freezes appears when gdm pop up the usual (you are already logged in as X, to you want to continue)

How to reproduce:
1. login as user X
2. system->Quit->Switch user
3. login in as user X again
4. a pop up start to appear and gdm freezes using 100% CPU

attach, a tar.gz of gdm strace while locking up. Summary from strace:
sort gdm-strace.txt | uniq -c
  28523 ioctl(3, FIONREAD, [0])                 = 0
    111 poll([{fd=3, events=POLLIN}], 1, 0)     = 0
  28522 poll([{fd=3, events=POLLIN}, {fd=3, events=POLLIN|POLLPRI}, {fd=7, events=POLLIN|POLLPRI, revents=POLLNVAL}], 3, 0) = 1

** Affects: gdm (Ubuntu)
     Importance: Undecided
         Status: Unconfirmed

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switching to current logged in user freezes gdm
https://launchpad.net/bugs/78470