RHEL server reboot hangs waiting on 'rw_semaphore' within the function vx_delay()

Issue

• The server was hung in the reboot process.
• "systemd-shutdown" itself stuck in an Uninterruptible state, waiting on rw_semaphore.

[ 2161.349492] INFO: task systemd-shutdow:13897 blocked for more than 120 seconds.
[ 2161.359368] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 2161.369784] systemd-shutdow D ffff99355eb98000     0 13897      1 0x00000084
[ 2161.379238] Call Trace:
[ 2161.383493]  [<ffffffff8bd9f12d>] ? list_del+0xd/0x30
[ 2161.390540]  [<ffffffff8c17f229>] schedule+0x29/0x70
[ 2161.397437]  [<ffffffff8c180c15>] rwsem_down_read_failed+0x105/0x1c0
[ 2161.405774]  [<ffffffff8bc7d870>] ? generic_write_sync+0x70/0x70
[ 2161.413674]  [<ffffffff8bd90b88>] call_rwsem_down_read_failed+0x18/0x30
[ 2161.422181]  [<ffffffff8c17e3b0>] down_read+0x20/0x40
[ 2161.428934]  [<ffffffff8bc4cafa>] iterate_supers+0xaa/0x120
[ 2161.436214]  [<ffffffff8bc7db64>] sys_sync+0x44/0xb0
[ 2161.442834]  [<ffffffff8c18cede>] system_call_fastpath+0x25/0x2a