From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 F322037EFE6; Tue, 16 Jun 2026 21:17:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781644642; cv=none; b=oOQhzP4nLhRjZKQod00ftn0oBXd6JbgPbTmREF7KADFCxsWM23+wQlh5p6vQ/Qj20UREqIsdLrrwvZ8kRJUN648WbpcJis7LhkwdSn8fY/NMHdEqEXBX0zSceOLX8TIHmQY1HB15i+A0F74LqM0bByh9HU6/OkBd+O5HfAbzKeA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781644642; c=relaxed/simple; bh=QTMau5ie2GGEAKVBGPZRNG3hRy6adIvv5lbrYw+yI7Y=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=J9pbAcRSK1N2BqEcLwrGL/bGZn44WRNLG56blWun7cu9a4w7lvgrbcHzzzgq7Fm0MOVypF1balYdWPl9+U8wNI6SfYgTcYIfWf1gzKakzBtxMKpwQIFfHaB5G52QRXnTseoqJPxyMrbxNvbmRQLqqcMfYs5RhM+S6mztbC6PM8U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DrPAWzPo; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="DrPAWzPo" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7A8411F00A3A; Tue, 16 Jun 2026 21:17:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781644641; bh=NmootHN4igiCQs8RopCQPxrV4Rp0tI0uYhX2d5/vyBg=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=DrPAWzPozIAd8z0OeZ+cn5GcnA0lYsXw9qioSOB3wnNF/Gisatr1GakVW+8Dj+TbP WaJbfdg46Jwhx0sMo1uTfI2YHyQ0iSb2SldhS5PDDSLWj3yYzyvL7bN4p2U65MTAUv PzrOYNrhWG7s0b6PXS5nl1vCTXDry6bAIOPsPThUHM2M4/bTxENJCJsCDMGhBvCzd1 +/rJTSQIqdBDBsNufBqonhIwBIKUH0u7Hc/TXozvP03HeXsvjpsd9ABZ+8CU1L53e1 SPZ4vOzs0pURzmN1s0QufSkCufmL96dLt006EM54nUIIBFIwZZlWipICYdeJqexZlJ kBPtdv6u4ORiw== Date: Tue, 16 Jun 2026 14:17:19 -0700 From: Jakub Kicinski To: Peter Zijlstra Cc: Sebastian Andrzej Siewior , Petr Mladek , John Ogness , Sergey Senozhatsky , Vlad Poenaru , Thomas Gleixner , netdev@vger.kernel.org, "David S . Miller" , Eric Dumazet , Paolo Abeni , Simon Horman , Breno Leitao , Clark Williams , Steven Rostedt , linux-rt-devel@lists.linux.dev, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Frederic Weisbecker , Ingo Molnar , Vincent Guittot , Dietmar Eggemann , K Prateek Nayak Subject: Re: [PATCH net] netpoll: run NAPI poll in softirq context to avoid rq->lock self-deadlock Message-ID: <20260616141719.67684bf0@kernel.org> In-Reply-To: <20260616170257.GH49951@noisy.programming.kicks-ass.net> References: <20260610183621.3915271-1-vlad.wing@gmail.com> <20260611191114.5bc43a59@kernel.org> <20260616103529.Yh9Dxsjp@linutronix.de> <20260616170257.GH49951@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: linux-kernel@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 Tue, 16 Jun 2026 19:02:57 +0200 Peter Zijlstra wrote: > > So this is not an issue since commit 7eab73b18630e ("netconsole: convert > > to NBCON console infrastructure"). Because from here now on writes are > > deferred to the nbcon thread. So this purely about -stable in this case. > > Hmm, I thought netconsole had some reserved skbs and could to writes > 'atomic' like? That said, it was 2.6 era the last time I looked at > netconsole. Yes, that part is fine. The problem is that netconsole tries to reap Tx completions if the Tx queue is full. We can't call skb destructor in irq context so we put the completed skbs on a queue and try to arm softirq to get to them later. Arming softirq causes a ksoftirq wake up. We already skip the completion polling if we detect getting called from the same networking driver. It's best effort, anyway. Networking-side fix would be to toss another OR condition into the skip. But we don't have one that'd work cleanly :S