linux-kernel - Re: [REGRESSION] Boot hang with 939f04bec printk: enable interrupts before calling console_trylock_for

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Date:	Thu, 3 Jul 2014 02:57:15 +0200
From:	Andreas Bombe <aeb@...ian.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, Jan Kara <jack@...e.cz>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [REGRESSION] Boot hang with 939f04bec printk: enable interrupts
 before calling console_trylock_for_printk()

On Mon, Jun 30, 2014 at 01:20:30PM -0700, Andrew Morton wrote:
> On Sun, 29 Jun 2014 00:50:50 +0200 Andreas Bombe <aeb@...ian.org> wrote:
> 
> > None of the post 3.15 kernel boot for me. They all hang at the GRUB
> > screen telling me it loaded and started the kernel, but the kernel
> > itself stops before it prints anything (or even replaces the GRUB
> > background graphics).
> > 
> > I bisected it down to 939f04bec1a4ef6ba4370b0f34b01decc844b1b1 "printk:
> > enable interrupts before calling console_trylock_for_printk()".
> > Reverting that patch on the latest kernel (git 24b414d5a7) allows me to
> > boot normally.
> 
> OK, thanks, I queued the below reversion.  I'll hold off for a week or
> two in case we come up with a fix.
> 
> > I fixed the conflict in the revert by leaving in the "if
> > (in_sched) return printed_len;".
> 
> hm, that might have been buggy - we still need to the lockdep_on() and
> local_irq_restore().  You're a victim of
> someone-stuck-a-random-return-in-the-middle-of-a-function.

To be honest, I just randomly picked one possible conflict resolution to
confirm whether the revert actually helps.

> Please review this and if possible, run-time test it?  Against current
> mainline.

I've applied it (actually I picked the one from your patch series but
they are identical I think) and it does boot. I'm writing this on the
latest kernel + your revert.
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