linux-kernel - Re: [RFC PATCH v4 9/9] printk: use a new ringbuffer implementation

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Message-ID: <20190809061437.GE2332@hirez.programming.kicks-ass.net>
Date:   Fri, 9 Aug 2019 08:14:37 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     John Ogness <john.ogness@...utronix.de>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrea Parri <andrea.parri@...rulasolutions.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Brendan Higgins <brendanhiggins@...gle.com>
Subject: Re: [RFC PATCH v4 9/9] printk: use a new ringbuffer implementation

On Thu, Aug 08, 2019 at 12:07:28PM -0700, Linus Torvalds wrote:

> End result: a DRAM buffer can work, but is not "reliable".
> Particularly if you turn power on and off, data retention of DRAM is
> iffy. But it's possible, at least in theory.
> 
> So I have a patch that implements a "stupid ring buffer" for thisa
> case, with absolutely zero data structures (because in the presense of
> DRAM corruption, all you can get is "hopefully only slightly garbled
> ASCII".

Note that you can hook this into printk as a fake early serial device;
just have the serial device write to the DRAM buffer.