Re: [PATCH v7 bpf-next 0/9] introduce support for XDP programs in CPUMAP

Jakub Sitnicki
2020-07-17T15:13:41Z

On Fri, 17 Jul 2020 13:01:36 +0200
Lorenzo Bianconi <lorenzo@kernel.org> wrote:

> [...]
>
> > This started showing up with when running ./test_progs from recent
> > bpf-next (bfdfa51702de). Any chance it is related?
> >
> > [ 2950.440613] =============================================
> >
> > [ 3073.281578] INFO: task cpumap/0/map:26:536 blocked for more than 860 seconds.
> > [ 3073.285492] Tainted: G W 5.8.0-rc4-01471-g15d51f3a516b #814
> > [ 3073.289177] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > [ 3073.293021] cpumap/0/map:26 D 0 536 2 0x00004000
> > [ 3073.295755] Call Trace:
> > [ 3073.297143] __schedule+0x5ad/0xf10
> > [ 3073.299032] ? pci_mmcfg_check_reserved+0xd0/0xd0
> > [ 3073.301416] ? static_obj+0x31/0x80
> > [ 3073.303277] ? mark_held_locks+0x24/0x90
> > [ 3073.305313] ? cpu_map_update_elem+0x6d0/0x6d0
> > [ 3073.307544] schedule+0x6f/0x160
> > [ 3073.309282] schedule_preempt_disabled+0x14/0x20
> > [ 3073.311593] kthread+0x175/0x240
> > [ 3073.313299] ? kthread_create_on_node+0xd0/0xd0
> > [ 3073.315106] ret_from_fork+0x1f/0x30
> > [ 3073.316365]
> > Showing all locks held in the system:
> > [ 3073.318423] 1 lock held by khungtaskd/33:
> > [ 3073.319642] #0: ffffffff82d246a0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x28/0x1c3
> >
> > [ 3073.322249] =============================================
>
> Hi Jakub,
>
> can you please provide more info? can you please identify the test that trigger
> the issue? I run test_progs with bpf-next master branch and it works fine for me.
> I run the tests in a vm with 4 vcpus and 4G of memory.
>
> Regards,
> Lorenzo
>

Was able to trigger it running the newly added selftest:

virtme-init: console is ttyS0
bash-5.0# ./test_progs -n 100
#100/1 cpumap_with_progs:OK
#100 xdp_cpumap_attach:OK
Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED
bash-5.0# [ 247.177168] INFO: task cpumap/0/map:3:198 blocked for more than 122 seconds.
[ 247.181306] Not tainted 5.8.0-rc4-01456-gbfdfa51702de #815
[ 247.184487] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 247.188876] cpumap/0/map:3 D 0 198 2 0x00004000
[ 247.192624] Call Trace:
[ 247.194327] __schedule+0x5ad/0xf10
[ 247.196860] ? pci_mmcfg_check_reserved+0xd0/0xd0
[ 247.199853] ? static_obj+0x31/0x80
[ 247.201917] ? mark_held_locks+0x24/0x90
[ 247.204398] ? cpu_map_update_elem+0x6d0/0x6d0
[ 247.207098] schedule+0x6f/0x160
[ 247.209079] schedule_preempt_disabled+0x14/0x20
[ 247.211863] kthread+0x175/0x240
[ 247.213698] ? kthread_create_on_node+0xd0/0xd0
[ 247.216054] ret_from_fork+0x1f/0x30
[ 247.218363]
[ 247.218363] Showing all locks held in the system:
[ 247.222150] 1 lock held by khungtaskd/33:
[ 247.224894] #0: ffffffff82d246a0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x28/0x1c3
[ 247.231113]
[ 247.232335] =============================================
[ 247.232335]

qemu running with 4 vCPUs, 4 GB of memory. .config uploaded at
https://paste.centos.org/view/0c14663d

HTH,
-jkbs