powerpc/watchdog: remove arch_trigger_cpumask_backtrace

[Michael Ellerman]

On Wed, 2018-01-17 at 12:47:22 UTC, Nicholas Piggin wrote:
> The powerpc NMI IPIs may not be recoverable if they are taken in
> some sections of code, and also there have been and still are issues
> with taking NMIs (in KVM guest code, in firmware, etc) which makes them
> a bit dangerous to use.
> 
> Generic code like softlockup detector and rcu stall detectors really
> hammer on trigger_*_backtrace, which has lead to further problems
> because we've implemented it with the NMI.
> 
> So stop providing NMI backtraces for now. Importantly, the powerpc code
> uses NMI IPIs in crash/debug, and the SMP hardlockup watchdog. So if the
> softlockup and rcu hang detection traces are not being printed because
> the CPU is stuck with interrupts off, then the hard lockup watchdog
> should get it with the NMI IPI.
> 
> Fixes: 2104180a5369 ("powerpc/64s: implement arch-specific hardlockup watchdog")
> Signed-of-by: Nicholas Piggin <npiggin at gmail.com>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/47712a921bb781caf69fca9eae43be

cheers