RHEL5.6 kernel oops when removing a path via sysfs interface following Kbase procedure

Issue

• Removing a one of the paths in an mpath device using DOC-3942 caused kernel crash
• Issuing "echo 1 > /sys/block/sdaa/device/delete" on a path in a multipath device causes kernel crash

• The following sequence of commands may cause a kernel crash.  A similar sequence several times before without issue.

  # multipath -ll<snip>
  mpath5 (360060480000190101119533030364430) dm-3 EMC,SYMMETRIX
  [size=2.0G][features=1 queue_if_no_path][hwhandler=0][rw]
  \_ round-robin 0 [prio=4][active]
   \_ 0:0:1:9  sdaa 65:160 [active][ready]
   \_ 1:0:0:9  sdav 66:240 [active][ready]
   \_ 1:0:1:9  sdbq 68:64  [active][ready]
   \_ 0:0:0:9  sdf  8:80   [active][ready]
  <snip>
  # echo 1 > /sys/block/sdaa/device/delete
  # echo 1 > /sys/block/sdav/device/delete
  *crash* message 
  

• kernel oops with the following backtrace:

  PID: 6391   TASK: ffff810fea0440c0  CPU: 1   COMMAND: "multipathd"
  #0 [ffff810fe557b950] crash_kexec at ffffffff800af897
   #1 [ffff810fe557ba10] __die at ffffffff80065117
   #2 [ffff810fe557ba50] do_page_fault at ffffffff8006748d
   #3 [ffff810fe557bb40] error_exit at ffffffff8005dde9
      [exception RIP: mutex_unlock]
      RIP: ffffffff80063a9c  RSP: ffff810fe557bbf0  RFLAGS: 00010206
  #4 [ffff810fe557bbf0] bd_release_from_disk at ffffffff800e726b
   #5 [ffff810fe557bc20] close_dev at ffffffff88259f83 [dm_mod]
   #6 [ffff810fe557bc30] dm_put_device at ffffffff88259fb3 [dm_mod]
   #7 [ffff810fe557bc40] free_priority_group at ffffffff884e74de [dm_multipath]
   #8 [ffff810fe557bc80] free_multipath at ffffffff884e7537 [dm_multipath]
   #9 [ffff810fe557bcb0] dm_table_put at ffffffff88259d9c [dm_mod]
  #10 [ffff810fe557bcd0] dm_swap_table at ffffffff8825947e [dm_mod]
  #11 [ffff810fe557bd00] dev_suspend at ffffffff8825c5ff [dm_mod]
  #12 [ffff810fe557bd30] ctl_ioctl at ffffffff8825cea4 [dm_mod]
  #13 [ffff810fe557beb0] do_ioctl at ffffffff80042426
  #14 [ffff810fe557bed0] vfs_ioctl at ffffffff800303df
  #15 [ffff810fe557bf40] sys_ioctl at ffffffff8004c8fc
  #16 [ffff810fe557bf80] system_call at ffffffff8005d116
      RIP: 00000032d38ccda7  RSP: 0000000041bf6968  RFLAGS: 00010202