linux-kernel - RE: [RFC PATCH 1/5] printk: implement pr_cont

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Date:   Thu, 20 Aug 2020 12:33:23 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Petr Mladek' <pmladek@...e.com>,
        John Ogness <john.ogness@...utronix.de>
CC:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [RFC PATCH 1/5] printk: implement pr_cont_t

From: Petr Mladek
> Sent: 20 August 2020 11:16
...
> Now that I think about it. This is the biggest problem with any temporary buffer
> for pr_cont() lines. I am more and more convinced that we should just
> _keep the current behavior_. It is not ideal. But sometimes mixed
> messages are always better than lost ones.

Maybe a marker to say 'more expected' might be useful.
OTOH lack of a trailing '\n' probably signifies that a
pr_cont() is likely to be next.

Unexpected pr_cont() could be output with a leading "... "
to help indicate the message is a continuation.

> That said, some printk() API using local buffer would be still
> valuable for pieces of code where people really want to avoid
> mixed lines. But it should be optional and people should be
> aware of the risks.

That could be very useful if it supported multi-line output.
Thing like the stack backtrace code could use it avoid
the mess that happens when multiple processes generate
tracebacks at the same time.

	David

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