From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759331AbcKCRdD (ORCPT ); Thu, 3 Nov 2016 13:33:03 -0400 Received: from mail-yb0-f174.google.com ([209.85.213.174]:34926 "EHLO mail-yb0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757963AbcKCRdC (ORCPT ); Thu, 3 Nov 2016 13:33:02 -0400 Date: Fri, 4 Nov 2016 02:31:53 +0900 From: Sergey Senozhatsky To: Joe Perches Cc: Sergey Senozhatsky , Jiri Kosina , Theodore Tso , Hannes Reinecke , Jan Kara , Petr Mladek , linux-kernel@vger.kernel.org Subject: Re: printk considered harmful (was: [TECH TOPIC] asynchronous printk) Message-ID: <20161103173153.GA423@swordfish> References: <1478106396.23018.51.camel@perches.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1478106396.23018.51.camel@perches.com> User-Agent: Mutt/1.7.1 (2016-10-04) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [Cc linux-kernel] Hello, On (11/02/16 10:06), Joe Perches wrote: > Hello all. > > Can you please post notes for whatever is proposed here somewhere? we covered 4 topics: #1 deadlocks and recursion in printk discussion outcome: I published an updated printk_safe patch last week (addresses recursion problems in printk). there was no strong opposition, and we agreed that per-cpu buffers can help us out. discussion outcome: we agreed that deadlocks in printk must be addressed via printk indirection. basically printk() will behave the same way as printk_deferred() and, thus, we can, at some point, remove printk_deferred(). #2 async printk discussion outcome: we agreed to offload printing duty to a special printk kthread. #3 pr_cont discussion outcome: out of "problems" list. no work will be done in this area. #4 console semaphore discussion outcome: we agreed that we can do better here and that it makes sense to do what's been proposed in my slides. but, I keep it as a low priority. frankly. I'd be happy to see #1-#3 in the mainline in 9-12 months. not because it's such an enormesoly hard thing to do, but because we probably would want to introduce those changes iteratively, in different releases. p.s. I uploaded "some sort" of slides to http://www.slideshare.net/SergeySENOZHATSKY/printk-considered-harmful -ss