Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753404AbdHWFo1 (ORCPT ); Wed, 23 Aug 2017 01:44:27 -0400 Received: from mail-pg0-f47.google.com ([74.125.83.47]:37759 "EHLO mail-pg0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753240AbdHWFoW (ORCPT ); Wed, 23 Aug 2017 01:44:22 -0400 Date: Wed, 23 Aug 2017 14:44:38 +0900 From: Sergey Senozhatsky To: Boqun Feng Cc: Sergey Senozhatsky , Byungchul Park , Bart Van Assche , peterz@infradead.org, "linux-kernel@vger.kernel.org" , "linux-block@vger.kernel.org" , "martin.petersen@oracle.com" , "axboe@kernel.dk" , "linux-scsi@vger.kernel.org" , "sfr@canb.auug.org.au" , "linux-next@vger.kernel.org" , kernel-team@lge.com Subject: Re: possible circular locking dependency detected [was: linux-next: Tree for Aug 22] Message-ID: <20170823054438.GA728@jagdpanzerIV.localdomain> References: <20170822183816.7925e0f8@canb.auug.org.au> <20170822104708.GA491@jagdpanzerIV.localdomain> <1503438234.2508.27.camel@wdc.com> <20170823000304.GK20323@X58A-UD3R> <20170823034951.GG11771@tardis> <20170823043813.GH11771@tardis> <20170823044648.GE10329@jagdpanzerIV.localdomain> <20170823053501.GJ11771@tardis> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170823053501.GJ11771@tardis> User-Agent: Mutt/1.8.3 (2017-05-23) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1040 Lines: 33 On (08/23/17 13:35), Boqun Feng wrote: [..] > > > printk(KERN_CONT ");\n"); > > > > KERN_CONT and "\n" should not be together. "\n" flushes the cont > > buffer immediately. > > > > Hmm.. Not quite familiar with printk() stuffs, but I could see several > usages of printk(KERN_CONT "...\n") in kernel. > > Did a bit research myself, and I now think the inappropriate use is to > use a KERN_CONT printk *after* another printk ending with a "\n". Am I > missing some recent changes or rules of KERN_CONT? has been this way for quite some time (if not always). LOG_NEWLINE results in cont_flush(), which log_store() the content of KERN_CONT buffer. if we see that supplied message has no \n then we store it in a dedicated buffer (cont buffer) if (!(lflags & LOG_NEWLINE)) return cont_add(); return log_store(); we flush that buffer (move its content to the kernel log buffer) when we receive a message with a \n or when printk() from another task/context interrupts the current cont line and, thus, forces us to flush. -ss