[GIT PULL] More printk hotfixes for 7.3

[Petr Mladek <pmladek@suse.com>]

Hi Linus,

please pull 2 more hot-fixes from

  git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux.git tags/printk-for-7.3-hotfix

================================================================

- Switch NBCON consoles to the emergency mode in emergency_restart() to
  see messages even in this shutdown code path.

- Postpone the start of printk kthreads after smp_init(). It prevents
  boot stalls on some HW.

- Typo fix in a previous hot-fix patch.

----------------------------------------------------------------

The postponed start of printk kthreads obviously looks like a workaround.
I wish we understood what was going on there.

It seems that it happens only on some (likely) older hardware.
John was not able to reproduce it on several systems so we were
not able to put hands on it.

We double checked the nbcon design and were not able to find any
location where it might cause a deadlock.

It rather looks like a HW specific problem. I do not have enough
experience with HW-specific bugs so it is not easier for me to
focus on some particular code path. It just seems that smp_init()
is not happy when another CPU is emitting the messages on the serial
port (manipulating interrupts?).

Anyway, the change looks safe. It just prolongs the time when
printk() tries to flush the messages directly even on NBCON
consoles. It might slowdown the boot a bit. But it won't be
worse than in the pre-NBCON era. And the direct flushing
increases the chance to see the messages. It makes printk()
more reliable for longer early boot period so some people
might even like this change.

I want to continue debugging of the problem. But let's move 7.3
to the safe side.

----------------------------------------------------------------
John Ogness (1):
      printk: Postpone kthread startup

Muhammad Mahdi Amirpour (1):
      printk: fix kernel-doc name for nbcon_write_context_is_braille

Petr Mladek (2):
      nbcon/reboot: Switch NBCON consoles into the emergency mode in emergency_restart()
      Merge branch 'for-7.3-hotfix' into for-linus

 kernel/printk/nbcon.c  | 3 ++-
 kernel/printk/printk.c | 2 +-
 kernel/reboot.c        | 9 +++++++++
 3 files changed, 12 insertions(+), 2 deletions(-)