serial: kgdboc: Fix NMI-safety problems from keyboard reset code

serial: kgdboc: Fix NMI-safety problems from keyboard reset code

Currently, when kdb is compiled with keyboard support, then we will use
schedule_work() to provoke reset of the keyboard status.  Unfortunately
schedule_work() gets called from the kgdboc post-debug-exception
handler.  That risks deadlock since schedule_work() is not NMI-safe and,
even on platforms where the NMI is not directly used for debugging, the
debug trap can have NMI-like behaviour depending on where breakpoints
are placed.

Fix this by using the irq work system, which is NMI-safe, to defer the
call to schedule_work() to a point when it is safe to call.

Reported-by: Liuye <liu.yeC@h3c.com>
Closes: https://lore.kernel.org/all/20240228025602.3087748-1-liu.yeC@h3c.com/
Cc: stable@vger.kernel.org
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20240424-kgdboc_fix_schedule_work-v2-1-50f5a490aec5@linaro.org
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>