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

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Date:   Fri, 17 Jul 2020 13:01:36 +0200
From:   Lorenzo Bianconi <lorenzo@...nel.org>
To:     Jakub Sitnicki <jakub@...udflare.com>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, ast@...nel.org,
        brouer@...hat.com, daniel@...earbox.net, toke@...hat.com,
        lorenzo.bianconi@...hat.com, dsahern@...nel.org,
        andrii.nakryiko@...il.com, bpf@...r.kernel.org
Subject: Re: [PATCH v7 bpf-next 0/9] introduce support for XDP programs in
 CPUMAP

[...]

> 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

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