linux-kernel - Re: pr_cat() + CATSTR(name, size)?

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Message-ID: <1342020647.13724.71.camel@joe2Laptop>
Date:	Wed, 11 Jul 2012 08:30:47 -0700
From:	Joe Perches <joe@...ches.com>
To:	Kay Sievers <kay@...y.org>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: pr_cat() + CATSTR(name, size)?

On Wed, 2012-07-11 at 17:14 +0200, Kay Sievers wrote:
> On Wed, Jul 11, 2012 at 5:01 PM, Joe Perches <joe@...ches.com> wrote:
[]
> There are _many_ cases the console lock is held, and we don't print
> stuff immediately out to the console, and we never ensured that in the
> past. There was never a guarantee that stuff ended up on the console,
> kmsg was always and needs to be a store+forward model.

I'm less concerned with kmsg than you.
I think it's more a nicety than anything.

> > It would require all sites with continuation lines
> > be modified.  Because it requires in-situ code
> > modifications, I'd prefer a cookie based approach.
> 
> Well, it would be mostly for the dev_printk() stuff, which should
> ideally never be merged with stuff that could go wrong.

Perhaps that's ideal, but not practical.
printk continuations are more prevalent.

> > I think it's more flexible, allows the cookie to be
> > passed into extending functions and doesn't demand
> > (much) extra stack.
> >
> > Something like:
> > https://lkml.org/lkml/2012/4/3/231
> > https://lkml.org/lkml/2011/11/14/349
> 
> Hmm, how do we manage memory allocations here? We can get around that
> somehow? It's something the common printk() must really avoid.

Well, I think the malloc costs are pretty low
and could devolve pretty easily when OOM.

cookie=NULL, directly emit.

Anyway, interesting idea, keep at it, see what
comes out of it.

cheers, Joe

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