linux-kernel - Re: POC: Alternative solution: Re: [PATCH 0/4] printk: reimplement LOG

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Message-ID: <20200815054143.GD582@jagdpanzerIV.localdomain>
Date:   Sat, 15 Aug 2020 14:41:43 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Petr Mladek <pmladek@...e.com>,
        John Ogness <john.ogness@...utronix.de>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        kexec@...ts.infradead.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: POC: Alternative solution: Re: [PATCH 0/4] printk: reimplement
 LOG_CONT handling

On (20/08/14 15:46), Linus Torvalds wrote:
> On Thu, Aug 13, 2020 at 4:54 AM Sergey Senozhatsky
> <sergey.senozhatsky@...il.com> wrote:
> >
> > I think what Linus said a long time ago was that the initial purpose of
> > pr_cont was
> >
> >         pr_info("Initialize feature foo...");
> >         if (init_feature_foo() == 0)
> >                 pr_cont("ok\n");
> >         else
> >                 pr_cont("not ok\n");
> >
> >         And if init_feature_foo() crashes the kernel then the first printk()
> >         form panic() will flush the cont buffer.
> 
> Right.
> 
> This is why I think any discussion that says "people should buffer
> their lines themselves and we should get rid if pr_cont()" is
> fundamentally broken.

I think what we've been talking about so far was "how do we buffer
cont lines now", what are the problems of current buffering and what
can we do to make that buffering SMP safe (preserving the context of
broken cont buffer, etc. etc.). I don't think that anyone concluded
to just "s/pr_cont/printk/g", I don't see this.

	-ss