ARM: 9317/1: kexec: Make smp stop calls asynchronous

In the Linux kernel, the following vulnerability has been resolved:

ARM: 9317/1: kexec: Make smp stop calls asynchronous

If a panic is triggered by a hrtimer interrupt all online cpus will be

notified and set offline. But as highlighted by commit 19dbdcb8039c

("smp: Warn on function calls from softirq context") this call should

not be made synchronous with disabled interrupts:

softdog: Initiating panic

Kernel panic - not syncing: Software Watchdog Timer expired

WARNING: CPU: 1 PID: 0 at kernel/smp.c:753 smp_call_function_many_cond

unwind_backtrace:

show_stack

dump_stack_lvl

__warn

warn_slowpath_fmt

smp_call_function_many_cond

smp_call_function

crash_smp_send_stop.part.0

machine_crash_shutdown

__crash_kexec

panic

softdog_fire

__hrtimer_run_queues

hrtimer_interrupt

Make the smp call for machine_crash_nonpanic_core() asynchronous.