Rebooting while mdraid device is resyncing can stall reboot in RHEL 5

Issue

• If the md raid is in state "resync" when the reboot command is run then it stalls for several hours with messages like this :

  "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
  reboot        D ffffffff801546d1     0 10776      1                 307 (NOTLB)
   ffff810371ef7d98 0000000000000086 ffff81037e815068 ffffffff80050b3a
   ffff81037e815068 0000000000000008 ffff81037c5037a0 ffff81067fc18820
   0000020817efb32f 0000000000005802 ffff81037c503988 0000000d00000282
  Call Trace:
   [<ffffffff80050b3a>] blk_put_request+0x2d/0x45
   [<ffffffff880c57d5>] :megaraid_sas:megasas_issue_blocked_cmd+0x7a/0x94
   [<ffffffff800a2e5d>] autoremove_wake_function+0x0/0x2e
   [<ffffffff880c60a1>] :megaraid_sas:megasas_flush_cache+0x69/0x7c
   [<ffffffff880c6255>] :megaraid_sas:megasas_shutdown+0x17/0x25
   [<ffffffff801d064b>] device_shutdown+0x56/0x88
   [<ffffffff8009d545>] kernel_restart+0x9/0x46
   [<ffffffff8009d6cf>] sys_reboot+0x146/0x1c7
   [<ffffffff8003ad50>] hrtimer_try_to_cancel+0x4a/0x53
   [<ffffffff8005a12f>] hrtimer_cancel+0xc/0x16
   [<ffffffff80063ce9>] do_nanosleep+0x47/0x70
   [<ffffffff8005a01c>] hrtimer_nanosleep+0x58/0x118
   [<ffffffff800a4e22>] hrtimer_wakeup+0x0/0x22
   [<ffffffff8001df0b>] sigprocmask+0xb7/0xdb
   [<ffffffff800549ca>] sys_nanosleep+0x4c/0x62
   [<ffffffff8005d116>] system_call+0x7e/0x83
  

The only way to reboot is a hardware reset of the server.