Bug 394761

Description of problem:
The current sosreport passes the "-M" flag to lsof to prevent potential blocking
operations but that is insufficient. The sosreport progress meter also displays
100%, despite the fact that no progress is happening:

 Progress [###################100%##################][05:36/05:36]
 Progress [###################100%##################][05:40/05:40]

[...]

 Progress [###################100%##################][26:42/26:42]

13673 pts/8    Ss     0:00  |   \_ -bash
13711 pts/8    Sl+    0:02  |   |   \_ python /usr/sbin/sosreport
13908 pts/8    S+     0:00  |   |       \_ /usr/sbin/lsof -b +M -n -l
25471 pts/8    Z+     0:00  |   |       \_ [cp] <defunct>

I ran into this situation on a system where an admin had run a "umount -lf" of
an unresponsive NFS file system. This means that the mount is detached from the
namespace and "lazy-umounted" when all references to it close. Since entries in
/proc/<pid> directories may still point at entries in this file system the lsof
spawned by sosreport may block accessing them.

Version-Release number of selected component (if applicable):
sos-1.7-9.1.el5

How reproducible:
100% on this host.

Steps to Reproduce:
[ one example - there are probably lots more ]
1. Mount an nfs file system
2. Make the server go away
3. Try an operation on the fs (e.g. ls /mount/point)
4. Lazy/background umount (umount -fl /mount/point)
5. Run sosreport
  
Actual results:
sosreport appears to hang waiting for lsof. Progress reaches 100% but the clock
keeps on going up.


Expected results:
sosreport should never hang when run with the default options.