powerpc/rtas: Introduce rtas_get_sensor_fast() for IRQ handlers

[Michael Ellerman]

On Fri, 2015-17-07 at 10:46:58 UTC, Thomas Huth wrote:
> The EPOW interrupt handler uses rtas_get_sensor(), which in turn
> uses rtas_busy_delay() to wait for RTAS becoming ready in case it
> is necessary. But rtas_busy_delay() is annotated with might_sleep()
> and thus may not be used by interrupts handlers like the EPOW handler!
> This leads to the following BUG when CONFIG_DEBUG_ATOMIC_SLEEP is
> enabled:

When did we break this?

cheers