Soft Lockup in shrink_dentry_list+0x4e/0xe0

[Dave Chiluk]

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

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
"

The following changes to dcache have been tested to resolve the issue.
https://lkml.org/lkml/2014/5/4/7
even though the original stack trace differs, but still ends in shrink_dentry_list.

[Brad Figg (brad-figg)]

This bug is missing log files that will aid in diagnosing the problem. From a terminal window please run:

apport-collect 1354157

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.