Re: [REGRESSION] Boot hang with 939f04bec printk: enable interrupts before calling console_trylock_for_printk()

[Andreas Bombe <aeb@debian.org>]

On Mon, Jul 14, 2014 at 10:35:27AM +0200, Jan Kara wrote:
> On Sun 29-06-14 00:50:50, Andreas Bombe 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. I fixed the conflict in the revert by leaving in the "if
> > (in_sched) return printed_len;".
> > 
> > I have the "early printk via the EFI framebuffer" option enabled,
> > disabling it made no difference however.
>   Thanks for report. I've been on vacation so I'm replying with a delay. I
> believe this is one of the issues where this patch just uncovers underlying
> problem - I belive lockdep tries to report some locking issue in console
> driver code (this patch increased lockdep coverage of console driver code)
> however we are holding some locks in printk code which make lockdep
> deadlock. Can you try running with the attached patch?

EUNABLE

You forgot to attach a patch.