linux-kernel - Re: + printk-print-initial-logbuf-contents-before-re-enabling-interrupts.patch added to -mm tree

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Message-ID: <20140512171521.GF3685@quack.suse.cz>
Date:	Mon, 12 May 2014 19:15:21 +0200
From:	Jan Kara <jack@...e.cz>
To:	Will Deacon <will.deacon@....com>
Cc:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jan Kara <jack@...e.cz>,
	"mm-commits@...r.kernel.org" <mm-commits@...r.kernel.org>,
	"peterz@...radead.org" <peterz@...radead.org>,
	"kay@...y.org" <kay@...y.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: +
 printk-print-initial-logbuf-contents-before-re-enabling-interrupts.patch
 added to -mm tree

On Thu 08-05-14 15:34:07, Will Deacon wrote:
> Hi Alan,
> 
> On Wed, May 07, 2014 at 05:41:51PM +0100, One Thousand Gnomes wrote:
> > > Possibly, but I fear we'd incur the wrath of Alan after reading that other
> > > thread. Having a CONFIG_ option or similar to control the amount of printing
> > > we do is very similar to the command-line option Jan proposed in his series.
> > 
> > I've nothing against a configuration option, and having a printk that
> > queued most stuff to the serial IRQ handler on overflow and a boot option
> > of printk=synchronous for debug work would be awesome in my book. Many end
> > production boxes don't give a toss about losing the odd bit of data they
> > just need to shift the logs somewhere for filing.
> 
> Ok, I'll revisit this with a command-line option for the debug case. Thanks.
> 
> > All these "clever" approaches just seem to me to be ever more convoluted
> > attempts to fail to deal with the simple reality that if you put more
> > down the sewage pipe than fits it has to overflow somewhere.
> >
> > Our tty drivers have a fifo, our tty drivers have an IRQ driven write
> > operation. It seems silly to be adding magic to solve the problem rather
> > than just using it (and in turn getting a ton of other consoles for free,
> > and being able to take GregKH's current usb console hack out)
> 
> Hmm, I'm not at all familiar with the tty layer, so I'd have to go and take
> a look. Jan, did you look at this at all?
  No. I know nothing about tty layer as well so this research task is
currently on a backburner...

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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