From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A07B3C433EF for ; Mon, 13 Jun 2022 11:50:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1356258AbiFMLuJ (ORCPT ); Mon, 13 Jun 2022 07:50:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60688 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1356275AbiFMLoQ (ORCPT ); Mon, 13 Jun 2022 07:44:16 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3FE0046CA8 for ; Mon, 13 Jun 2022 03:50:38 -0700 (PDT) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id 94C4621C6E; Mon, 13 Jun 2022 10:50:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1655117431; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=17/3CEJujfFLNuAQBHZxH41y/BnqBjSR48wov2fqM/c=; b=jsn1Bbn3KdWZklFqk+mXqUxZUX4hqzl0edsHWICFEPtWCiWWEwgCsH9264lqYdbRk91Oh0 TItVqszzHUyQezUUDAG6XgmdWz8kveKvNWR/PQHPbpIT7uE0xU3JjIXjUlMe1D7uFpELx2 36hBK7JNegpR2rwYjKDgbuuRxA8wNJI= Received: from suse.cz (unknown [10.100.201.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 70D812C141; Mon, 13 Jun 2022 10:50:31 +0000 (UTC) Date: Mon, 13 Jun 2022 12:50:31 +0200 From: Petr Mladek To: "Paul E. McKenney" Cc: john.ogness@linutronix.de, linux-kernel@vger.kernel.org, frederic@kernel.org Subject: Re: [BUG] 8e274732115f ("printk: extend console_lock for per-console locking") Message-ID: References: <20220610205038.GA3050413@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220610205038.GA3050413@paulmck-ThinkPad-P17-Gen-1> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 2022-06-10 13:50:38, Paul E. McKenney wrote: > Hello, John, > > I have started getting rcutorture shutdown-time hangs when running > against recent mainline, and bisected back to the 8e274732115f ("printk: > extend console_lock for per-console locking") commit. These hangs go > away (or at least their probability drops dramatically) if I build with > CONFIG_PREEMPTION=n -and- CONFIG_NO_HZ=y (not n!), at least assuming > that I also boot with "nohz_full=0-N". This means that the kthreads are probably more often sleeping with con->lock when the pre-emtion is done by regular ticks. We might want to wake them if we could call pr_flush(). But we could not do this in the generic panic() path. It might cause deadlock when panic() is called from scheduler code. Pest Regards, Petr