linux-kernel - Re: [PATCH v5 4/4] printk: use the lockless ringbuffer

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Message-ID: <20200719034312.GA566736@jagdpanzerIV.localdomain>
Date:   Sun, 19 Jul 2020 12:43:12 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     Marco Elver <elver@...gle.com>
Cc:     John Ogness <john.ogness@...utronix.de>,
        Petr Mladek <pmladek@...e.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrea Parri <parri.andrea@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Paul McKenney <paulmck@...nel.org>, kexec@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 4/4] printk: use the lockless ringbuffer

Hi Marco,

On (20/07/18 14:10), Marco Elver wrote:
> 
> It seems this causes a regression observed at least with newline-only
> printks. I noticed this during -next testing because various debugging
> tools (K*SAN, lockdep, etc.) use e.g. pr_{err,warn,info}("\n") to format
> reports.
> 
> Without wanting to wait for a report from one of these debugging tools,
> a simple reproducer is below. Without this patch, the expected newline
> is printed.

Empty/blank lines carry no valuable payload, could you please explain
why do you consider this to be a regression?

	-ss