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 9EC1CC00140 for ; Tue, 2 Aug 2022 07:37:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235981AbiHBHhm (ORCPT ); Tue, 2 Aug 2022 03:37:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42820 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235987AbiHBHhf (ORCPT ); Tue, 2 Aug 2022 03:37:35 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C588FB86E for ; Tue, 2 Aug 2022 00:37:33 -0700 (PDT) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id 573EA203AE; Tue, 2 Aug 2022 07:37:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1659425852; 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=I/fg8txpSAtyJTnoIbKN0qFtAj2rAgtTdzaptbHxtuM=; b=Ru6r0D+lF4I/Kh4I/7Y6rPWQemGjTV8up7B6jv+mB2WhLw5B5kEFCFOCRuq+Wq8h0zl3t9 R3zPpL1gwaSj1mMENZHQZJMURoZBbR9jc9c775mt7SUrr5BLsGKAtcQjTUjimSBembgUyI Hr32aOx6OyqL7WVZ/HgJTvaolMGR2w0= 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 713092C141; Tue, 2 Aug 2022 07:37:31 +0000 (UTC) Date: Tue, 2 Aug 2022 09:37:28 +0200 From: Petr Mladek To: David Laight Cc: Linus Torvalds , Sergey Senozhatsky , Steven Rostedt , John Ogness , Andy Shevchenko , Rasmus Villemoes , Sebastian Andrzej Siewior , Thomas Gleixner , Jan Kara , Peter Zijlstra , "linux-kernel@vger.kernel.org" Subject: Re: [GIT PULL] printk for 5.20 Message-ID: References: <16ef8dbc4bdf4120b046ebacaf1f3cf2@AcuMS.aculab.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <16ef8dbc4bdf4120b046ebacaf1f3cf2@AcuMS.aculab.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 2022-08-01 15:45:13, David Laight wrote: > > - Completely disable printing on consoles with CONFIG_RT. They break > > RT guarantees. They are too slow to be called with raw spinlocks. > > They can't be called with normal spinlocks in an atomic context because > > RT spinlocks might sleep. It is going to get fixed by the kthreads and > > atomic consoles. In the meantime, the debugging of CONFIG_RT kernel > > will be possible only by the user space kernel log readers. > > SYSV used to be like that if you were running syslogd. > Used to make debugging some issues completely impossible. Sure. My understanding is that this is how RT guys want it in 4.19. There is no quick magic solution. Either printk() would break RT guarantees or messages will not be seen on consoles. The blank consoles were chosen as the least bad solution. Of course, we are still working on the printk kthreads and atomic consoles that would allow debugging using consoles on RT again. Best Regards, Petr