On Fri, Nov 27, 2015 at 12:09:30PM +0100, Petr Mladek wrote:

What we can do, though, is to zap all printk locks. We already do this
when a printk recursion is detected. This should be safe because
the system is crashing and there shouldn't be any printk caller
that would cause the deadlock.

What about serial consoles which may call out to subsystems like the
clk subsystem to enable a clock, which would want to take their own
spinlocks in addition to the serial console driver?

I don't see bust_spinlocks() dealing with any of these locks, so IMHO
trying to make this work in NMI context strikes me as making the
existing solution more unreliable on ARM systems.

-- 
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.