linux-kernel - Re: Printk mulitple line message support

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Date:	Mon, 14 Nov 2011 06:40:40 -0800
From:	Joe Perches <joe@...ches.com>
To:	Huang Ying <ying.huang@...el.com>
Cc:	William Douglas <william.r.douglas@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Printk mulitple line message support

On Mon, 2011-11-14 at 14:58 +0800, Huang Ying wrote:
> Hi,
> 
> In most cases, printk only guarantees messages from different printk
> calling will not be interleaved between each other.  But many printk
> users uses multiple line to form a complete message and call printk
> for each line.  So the following situation is possible for two printk
> users running on two CPUs.
> 
> line 1 of message from printk user1
> line 1 of message from printk user2
> line 2 of message from printk user1
> line 2 of message from printk user2
> 
> This makes kernel log hard to read.  One possible solution to this
> issue is to give a sequence number (or ID) to each complete message.
> So the above lines will be:
> 
> {1}line 1 of message from printk user1
> {2}line 1 of message from printk user2
> {1}line 2 of message from printk user1
> {2}line 2 of message from printk user2
> 
> Then some simple script can be used to group lines together according
> to sequence number in lines.
> 
> What do you think about that?

This makes the typical multi-part but non-interleaved
output difficult to read.

How about determining if there is interleaving and
emitting sequence # only in those cases?

Perhaps test the atomic for the last sequence #.


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