linux-kernel - update_balloon_size_func blocked for more than 120 seconds

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Date:   Thu, 11 Nov 2021 14:48:25 -0800
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     mst@...hat.com, david@...hat.com, jasowang@...hat.com,
        virtualization@...ts.linux-foundation.org,
        Michal Hocko <mhocko@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>
Cc:     Luis Chamberlain <mcgrof@...nel.org>, linux-kernel@...r.kernel.org
Subject: update_balloon_size_func blocked for more than 120 seconds

I get the following splats with a kvm guest in idle, after a few seconds
it starts:

[  242.412806] INFO: task kworker/6:2:271 blockedfor more than 120 seconds.
[  242.415790]       Tainted: G            E     5.15.0-next-20211111 #68
[  242.417755] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  242.418332] task:kworker/6:2     state:D stack:    0 pid:  271 ppid: 2 flags:0x00004000
[  242.418954] Workqueue: events_freezable update_balloon_size_func [virtio_balloon]
[  242.419518] Call Trace:
[  242.419709]  <TASK>
[  242.419873]  __schedule+0x2fd/0x990
[  242.420142]  schedule+0x4e/0xc0
[  242.420382]  tell_host+0xaa/0xf0 [virtio_balloon]
[  242.420757]  ? do_wait_intr_irq+0xa0/0xa0
[  242.421065]  update_balloon_size_func+0x2c9/0x2e0 [virtio_balloon]
[  242.421527]  process_one_work+0x1e5/0x3c0
[  242.421833]  worker_thread+0x50/0x3b0
[  242.422204]  ? rescuer_thread+0x370/0x370
[  242.422507]  kthread+0x169/0x190
[  242.422754]  ? set_kthread_struct+0x40/0x40
[  242.423073]  ret_from_fork+0x1f/0x30
[  242.423347]  </TASK>

And this goes on endlessly. The last one says it blocked for more than 1208
seconds. This was not happening until the last few weeks but I see no
relevant recent commits for virtio_balloon, so the related change could
be elsewhere.

I could bisect but first I figured I'd check to see if someone already
had spotted this.

  Luis