linux-kernel - Re: [PATCH] printk: git rid of [sched_delayed] message for printk

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Date:	Sat, 20 Sep 2014 20:01:48 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Joe Perches <joe@...ches.com>
Cc:	Jan Kara <jack@...e.cz>, Steven Rostedt <rostedt@...dmis.org>,
	Markus Trippelsdorf <markus@...ppelsdorf.de>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] printk: git rid of [sched_delayed] message for
 printk_deferred

On Sat, Sep 20, 2014 at 09:10:47AM -0700, Joe Perches wrote:
> On Sat, 2014-09-20 at 17:47 +0200, Peter Zijlstra wrote:
> > On a whole, printk() is entirely useless for debugging these days, its
> > far too fragile/unreliable to be taken seriously so I really don't care
> > on that point either.
> 
> That's unfortunate.
> 
> Care to enumerate the issues that you believe make
> printk too fragile/unreliable for debugging?

Look at what it takes to end up at console->write(), and then realize
that some console implementations require scheduling and other nonsense
to actually implement ->write().

The (only) reliable option is early_printk() with the
early_serial_console driver. The rest is useless crap these days.
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