linux-kernel - Re: [RFC PATCH v2 1/2] printk-rb: add a new printk ringbuffer implementation

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Message-ID: <20190626075910.GA2936@jagdpanzerIV>
Date:   Wed, 26 Jun 2019 16:59:10 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Petr Mladek <pmladek@...e.com>
Cc:     John Ogness <john.ogness@...utronix.de>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrea Parri <andrea.parri@...rulasolutions.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: [RFC PATCH v2 1/2] printk-rb: add a new printk ringbuffer
 implementation

On (06/26/19 09:47), Petr Mladek wrote:
[..]
> If the data might change under the hood then we have bigger
> problems. For example, there might be a race when the trailing
> "\0" has not been written yet.

Current printk would not handle such cases. I'm only talking about
transition from one consistent state to another, when
	sprintf(NULL, ptr) == A && sprintf(buf, ptr) != A
Wether it's a corner case or not is entirely unclear to me but I
probably would not call it "an impossible scenario".

	-ss