linux-kernel - Re: [syzbot] [net?] INFO: task hung in new_device

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Message-ID: <a127c251-5d62-47c5-8ac0-37a490ed0c37@I-love.SAKURA.ne.jp>
Date: Tue, 30 Dec 2025 16:48:23 +0900
From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To: syzbot <syzbot+05f9cecd28e356241aba@...kaller.appspotmail.com>,
        andrew+netdev@...n.ch, boqun.feng@...il.com, davem@...emloft.net,
        edumazet@...gle.com, hdanton@...a.com, kuba@...nel.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        pabeni@...hat.com, syzkaller-bugs@...glegroups.com,
        torvalds@...ux-foundation.org
Subject: Re: [syzbot] [net?] INFO: task hung in new_device_store (5)

If we ratelimit

  "received packet on %s with own address as source address (addr:%pM, vlan:%u)\n",

message with up to once per 2 second [1], this problem is shown as "task hung in rtnl_lock".
If we ratelimit this message with up to 10 times per 5 second [2], this problem is shown as
"INFO: task hung in del_device_store".

This difference suggests that this task hung is caused by out of CPU time for making
forward progress due to spending too much CPU time for printk() operation from interrupt
context. We might want to ratelimit more aggressively.

Link: https://lkml.kernel.org/r/69533402.050a0220.329c0f.0428.GAE@google.com [1]
Link: https://lkml.kernel.org/r/695347ee.050a0220.329c0f.042b.GAE@google.com [2]