Comment 4 for bug 1354234

Here's a soft lockup that is reportedly fixed by this patchset

BUG: soft lockup - CPU#1 stuck for 23s! [test.sh:1928]
Kernel panic - not syncing: softlockup: hung tasks
CPU: 1 PID: 1928 Comm: test.sh Tainted: G W 3.13.0-24-generic #47-Ubuntu
Hardware name: NEC Mercury CPU Module [NQ2250-902]/GC-MDC10-NJ, BIOS 5.6.0005 03/05/2014
000000000000419b ffff88017fc43e28 ffffffff81715ac4 ffffffff81a5ee64
ffff88017fc43ea0 ffffffff8170ecc5 0000000000000008 ffff88017fc43eb0
ffff88017fc43e50 0000000000000086 00000000a954a952 0000000000000007
Call Trace:
<IRQ> [<ffffffff81715ac4>] dump_stack+0x45/0x56
[<ffffffff8170ecc5>] panic+0xc8/0x1d7
[<ffffffff8110d015>] watchdog_timer_fn+0x165/0x170
[<ffffffff8108e537>] __run_hrtimer+0x77/0x1d0
[<ffffffff8110ceb0>] ? watchdog_cleanup+0x10/0x10
[<ffffffff8108ed3f>] hrtimer_interrupt+0xef/0x230
[<ffffffff81043087>] local_apic_timer_interrupt+0x37/0x60
[<ffffffff8172887f>] smp_apic_timer_interrupt+0x3f/0x60
[<ffffffff8172721d>] apic_timer_interrupt+0x6d/0x80
<EOI> [<ffffffff8171da2c>] ? _raw_spin_lock+0x1c/0x50
[<ffffffff811d02ce>] shrink_dentry_list+0x4e/0xe0
[<ffffffff811d10f8>] shrink_dcache_parent+0x28/0x70
[<ffffffff81224826>] proc_flush_task+0xb6/0x1b0
[<ffffffff81068540>] release_task+0x30/0x440
[<ffffffff8109e1b1>] ? thread_group_cputime_adjusted+0x41/0x50
[<ffffffff8106922f>] wait_consider_task+0x8df/0xb20
[<ffffffff81069570>] do_wait+0x100/0x240
[<ffffffff8106a6a4>] SyS_wait4+0x64/0xe0
[<ffffffff810682a0>] ? task_stopped_code+0x60/0x60
[<ffffffff817266bf>] tracesys+0xe1/0xe6

Also some machines are able to reliably reproduce this soft lockup using the following script.
"
#!/bin/bash

mkdir -p testdir
cd testdir

while true; do if ! (exec >xx1 2>xx2 ; rm -f xx*; host www.google.com); then echo failed; fi ; done &
while true; do ls -lR /proc >& /dev/null; done &
while true; do lsof > /dev/null; done &
while true; do ls -H >& /dev/null; done &

wait
"
Although I personally have not been able to reproduce using this script.