From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 67F8929BDBF for ; Wed, 1 Oct 2025 17:22:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759339345; cv=none; b=H1GTocVePHhWEe91X2MHckEyqXjiCGvcYULWHuMmjgEpUK1x41x0Fx1oy59pJsib+O4I9qhCzoGjMBbM+SLbI4uNF0eBqI0ti8aL9ko9gaeIxCAs8xSDlpGyFcJF5hM2kq2o2HloBPuS97lru6YV5AdmrK7yMjcP/0RqRG83TVs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759339345; c=relaxed/simple; bh=er5fdosOTkZo6aWK98DMQCF7XfdpT0QQLYFvimi3dB0=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=bv5ubzc88YQcY1E8a6OnJccZAU1tv3pKgxl6R4lEO7Q49kRmL1YajJySjeIgvAgBQXlRkPOKuO6PJEickTR9v8lgW/svdoYBPqhmU0WrPiQCAsr033xZwFRTqplLgrqqnqsREXO1qYXZgH/WJgvl7b0xh/JinEkTvG552EfuwG4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=b3eBw3tm; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="b3eBw3tm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AB704C4CEF7; Wed, 1 Oct 2025 17:22:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1759339344; bh=er5fdosOTkZo6aWK98DMQCF7XfdpT0QQLYFvimi3dB0=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=b3eBw3tmH2aas4v7vZXH1nSWh1OOW3QOjAtHa2G+lVdxQhTCx/uZIiJxum5JhUOPc eD5yQbA87+LGwHCz4/WjlDLDmj6jR94H4++fvqWhH9rThfB2M1SPpG7ksRHoBD9h3g SAs1IRUz6RKWL8mQfyC8NksL/3wh7fBv5kSSI/tCRE7yBbN8D3ApKHs9OnEujVJMI0 d5dNcrSj2Pb8/zNr0nOU8B/QaFsel2ZWTh56HW9pTrcNFyAQCoV6akZbAL96bj6B8z 1mOftIZXFxRCB10233PHA2LlOzL8YWhD51Ld9JW7SmZMA1It0kM3BYxRN0TX0ixIHN Hs8MiwkzSM+nw== Date: Wed, 1 Oct 2025 10:22:23 -0700 From: Jakub Kicinski To: Paolo Abeni Cc: Eric Dumazet , Florian Westphal , Kuniyuki Iwashima , Willem de Bruijn , netdev@vger.kernel.org Subject: Re: deadlocks on pernet_ops_rwsem Message-ID: <20251001102223.1b8e9702@kernel.org> In-Reply-To: <3a8ba87f-a6ab-4523-b0ce-8e9dbd5a923b@redhat.com> References: <20251001082036.0fc51440@kernel.org> <3a8ba87f-a6ab-4523-b0ce-8e9dbd5a923b@redhat.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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 blocked on an rw-semaphore likely owned by task kworker/u16:0:12 but most are more useless: [ 4671.090728][ T44] INFO: task modprobe:2342 is blocked on an rw-semaphore, but the owner is not found. (?!?)