From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 75F0B1A6803; Wed, 17 Jun 2026 11:15:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781694921; cv=none; b=tBjLiS0nRg8hI/zx4MACZvVl1FCZ1kT3h/bAsfa5JcM3+SsUxqNZNZhS3l8jvSQtSeE5AcVe9TBdLke29hg/rpETIhAPaMuWBZwJOqVGRUGZ4nvwy6zvi7B6hFNtsqX4n6B/sj9/m17HEEC/jL6MN6dqzVsO2mxKrPLdc2zL8IE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781694921; c=relaxed/simple; bh=nBVIaKSsHHnhzWNXbdCl+T5AZ8DzxyZFY7wkUDzN4oE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=XvwqTdWiSV4x/kSJ6BtiA6tLdFBJ/ECqqtL0vIkSCn6YWi1gZuR9XjJam97vwPASobirheYHh3n15cJqt4VJAv1sEYIgYhXQ7u/r/s6MpHT8zszbE621/nSqiv1w5N+sPvpgxsJXcBetOkHJLYaUEKKEa+gBFy2YZcL/vRzw+JQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=pass smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=Y1AXNBND; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Y1AXNBND" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=meCnZyamFGP+bBE/4r/7JIL/zf4RCwFPKYvTk3wFM54=; b=Y1AXNBNDrx6/52jl+wRRaDAVnx aTeF1vWb594J4Qly4luv7i6USc7N9lF7HP104kQPtvBF2q+sNmKOmGoOkjp3SdH6eUHdpsXtWnetb I55g4s5NeqvPUf+OG98cAorUFy0zJ3BF+esnllmRtw43yKoWL781VNRBHiwWesZOQj2AqIH3At4RX 0WVrzkBsDcCsEOvMJOwvc8U7bWjqCmwDebuXR6t2mGGvCB2hnq4ukXKGmTgJrHMF3ChpNi13TTRG4 HxEH3h9UUv6gkg5mLat8LSdkAE6fSPPreMj+8y8aOJeitCriRkHRK86UodkAmHCo//JXx0j6coOkd bf+la3gA==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.99.1 #2 (Red Hat Linux)) id 1wZoEa-0000000CW6M-2zW4; Wed, 17 Jun 2026 11:15:05 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 330BE30036F; Wed, 17 Jun 2026 13:15:04 +0200 (CEST) Date: Wed, 17 Jun 2026 13:15:04 +0200 From: Peter Zijlstra To: Petr Mladek Cc: Sebastian Andrzej Siewior , Jakub Kicinski , 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: <20260617111504.GK49951@noisy.programming.kicks-ass.net> References: <20260610183621.3915271-1-vlad.wing@gmail.com> <20260611191114.5bc43a59@kernel.org> <20260616103529.Yh9Dxsjp@linutronix.de> <20260616081128.04e2c8dd@kernel.org> <20260616153122.keHMKvVT@linutronix.de> 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-Disposition: inline In-Reply-To: On Wed, Jun 17, 2026 at 12:12:07PM +0200, Petr Mladek wrote: > On Tue 2026-06-16 17:31:22, Sebastian Andrzej Siewior wrote: > > On 2026-06-16 08:11:28 [-0700], Jakub Kicinski wrote: > > > > > > > > Adding sched and printk folks for opinions while eyeballing > > > > WARN_ON_DEFERRED(). > > > > > > Thanks a lot for looking into this! To be clear - the printk_deferred / > > > WARN_DEFERRED would be just for stable? Or there's still some > > > sensitivity even with nbcon? > > > > We already have printk_deferred(). WARN_DEFERRED() would be new. I > > *think* this is not limited netpoll/ netconsole but all console drivers > > not using CON_NBCON if the printk (via WARN) occurs with the rq held. > > I don't remember all the details but printk_deferred() was introduced to > > circumvent this until printk is fixed. > > Just to make it clear. The problem with the legacy consoles is that > they are called under console_lock() which is a semaphore. And it > calls wake_up_process() in console_unlock() when there is another > waiter on the lock. > > > Once we get rid of those legacy drivers and NBCON is the default we can > > get rid of printk_deferred() :) > > Yup. Can't we push all the legacy consoles into a single legacy kthread? I mean, converting all consoles is of course awesome, but should we really wait for that?