From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751425AbdH1MUw (ORCPT ); Mon, 28 Aug 2017 08:20:52 -0400 Received: from mail-pf0-f195.google.com ([209.85.192.195]:37848 "EHLO mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751231AbdH1MUv (ORCPT ); Mon, 28 Aug 2017 08:20:51 -0400 Date: Mon, 28 Aug 2017 21:21:09 +0900 From: Sergey Senozhatsky To: Sergey Senozhatsky Cc: Pavel Machek , Sergey Senozhatsky , Petr Mladek , Steven Rostedt , Jan Kara , Andrew Morton , Jiri Slaby , Andreas Mohr , Tetsuo Handa , linux-kernel@vger.kernel.org Subject: Re: printk: what is going on with additional newlines? Message-ID: <20170828122109.GA532@jagdpanzerIV.localdomain> References: <20170815025625.1977-1-sergey.senozhatsky@gmail.com> <20170828090521.GA25025@amd> <20170828102830.GA403@jagdpanzerIV.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170828102830.GA403@jagdpanzerIV.localdomain> 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 On (08/28/17 19:28), Sergey Senozhatsky wrote: > On (08/28/17 11:05), Pavel Machek wrote: > > Hi! > > > > In 4.13-rc, printk("foo"); printk("bar"); seems to produce > > foo\nbar. That's... quite surprising/unwelcome. What is going on > > there? Are timestamps responsible? > > well, one thing we know for sure it is not related to this patch set ;) > > > does any of the below patches fix the problem for you? > > basically it sets up the rule -- if we don't have LOG_NEWLINE lflags > then we enforce LOG_CONT. [..] > @@ -1670,7 +1670,9 @@ static size_t log_output(int facility, int level, enum log_flags lflags, const c > * write from the same process, try to add it to the buffer. > */ > if (cont.len) { > if (cont.owner == current && (lflags & LOG_CONT)) { on the other hand... I don't think I like that check at all. so I *probably* want to change it to -- !LOG_NEWLINE messages of the same loglevel AND from the same task are getting concatenated. a message with LOG_NEWLINE flushes the cont buffer. for example: printk("foo"); printk("foo"); printk("bar\n"); printk("buz"); printk("buz"); printk("buz"); pr_info("INFO msg\n"); printk("buz"); printk("buz"); printk("buz"); pr_err("ERR msg\n"); printk(KERN_CONT"foo"); printk(KERN_CONT"foo"); printk(KERN_CONT"bar\n"); printk(KERN_CONT"foo"); printk(KERN_CONT"foo"); printk(KERN_ERR"bar\n"); printk(KERN_CONT"foo"); printk(KERN_ERR"foo err"); printk(KERN_ERR"bar err\n"); for instance, printk(KERN_ERR"foo err"); printk(KERN_ERR"bar err\n"); should produce "foo errbar err\n". from the same task and of the same loglevel, no new line. must be cont messages with a missing KERN_CONT. right? so, for the examples I posted above, I think, the output must be foofoobar buzbuzbuz INFO msg buzbuzbuz ERR msg foofoobar foofoo bar foo foo errbar err how about something like this? --- diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index fc47863f629c..675febf84dc8 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -1670,10 +1670,9 @@ static size_t log_output(int facility, int level, enum log_flags lflags, const c * write from the same process, try to add it to the buffer. */ if (cont.len) { - if (cont.owner == current && (lflags & LOG_CONT)) { + if (cont.owner == current && cont.level == level) if (cont_add(facility, level, lflags, text, text_len)) return text_len; - } /* Otherwise, make sure it's flushed */ cont_flush(); }