From: Jakub Kicinski <kuba@kernel.org>
To: Paolo Abeni <pabeni@redhat.com>
Cc: Eric Dumazet <edumazet@google.com>,
Florian Westphal <fw@strlen.de>,
Kuniyuki Iwashima <kuniyu@google.com>,
Willem de Bruijn <willemb@google.com>,
netdev@vger.kernel.org
Subject: Re: deadlocks on pernet_ops_rwsem
Date: Wed, 1 Oct 2025 10:22:23 -0700 [thread overview]
Message-ID: <20251001102223.1b8e9702@kernel.org> (raw)
In-Reply-To: <3a8ba87f-a6ab-4523-b0ce-8e9dbd5a923b@redhat.com>
On Wed, 1 Oct 2025 18:46:16 +0200 Paolo Abeni wrote:
> Not many here. The above are debug builds, so we should get a lockdep
> splat on deadlock, the logs lack it. I guess the request_module() breaks
> the lockdep checks?
To be clear -- AFAICT lockdep misses this.
The splat is from the "stuck task" checker.
2 min wait to load a module during test init would definitely be a sign
of something going sideways.. but I think it's worse than that, these
time out completely and we kill the VM. I think the modprobe is truly
stuck here.
In one of the splats lockdep was able to say:
[ 4302.448228][ T44] INFO: task modprobe:31634 <writer> blocked on an rw-semaphore likely owned by task kworker/u16:0:12 <reader>
but most are more useless:
[ 4671.090728][ T44] INFO: task modprobe:2342 is blocked on an rw-semaphore, but the owner is not found.
(?!?)
next prev parent reply other threads:[~2025-10-01 17:22 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-01 15:20 deadlocks on pernet_ops_rwsem Jakub Kicinski
2025-10-01 16:46 ` Paolo Abeni
2025-10-01 17:22 ` Jakub Kicinski [this message]
2025-10-01 18:50 ` Kuniyuki Iwashima
2025-10-01 19:26 ` Jakub Kicinski
2025-10-01 19:33 ` Willem de Bruijn
2025-10-01 20:30 ` Jakub Kicinski
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