tuna -P give me errors

Issue

• When I run 'tuna -P', I got errors like below, this is rhel 6.2, can you advise what the problem is?

• The calltraces may be identical to the following:

# tuna -P
                      thread       ctxt_switches
    pid SCHED_ rtpri affinity voluntary nonvoluntary             cmd
Traceback (most recent call last):
  File "/usr/bin/tuna", line 594, in <module>
    main()
  File "/usr/bin/tuna", line 489, in main
    kthreads, affect_children, show_sockets)
  File "/usr/bin/tuna", line 295, in do_ps
    has_ctxt_switch_info, sock_inodes, sock_inode_re)
  File "/usr/bin/tuna", line 248, in ps_show
    affinity = schedutils.get_affinity(pid)
OSError: [Errno 3] No such process

Or sometimes are seen as below:

 61878  OTHER     0 0xffffffff,0xffffffff      4464          313            sshd
  61879  OTHER     0 0xffffffff,0xffffffff       737           87            bash
  62544  OTHER     0 0xffffffff,0xffffffff        14            0      flush-0:26
Traceback (most recent call last):
  File "/usr/bin/tuna", line 594, in <module>
    main()
  File "/usr/bin/tuna", line 489, in main
    kthreads, affect_children, show_sockets)
  File "/usr/bin/tuna", line 295, in do_ps
    has_ctxt_switch_info, sock_inodes, sock_inode_re)
  File "/usr/bin/tuna", line 260, in ps_show
    sock_inode_re)
  File "/usr/bin/tuna", line 172, in ps_show_thread
    affinity = format_affinity(schedutils.get_affinity(pid))
OSError: [Errno 3] No such process