The ARM Cortex-M 321 application note is stressing that
when enabling interrupts by executing CPSIE i(f), or by MSR
instructions (on PRIMASK, FAULTMASK, or BASEPRI registers),
there is a need for synchronization barrier instructions,
if there is a requirement for the effect of enabling
interrupts to be recongnized immediately. _arch_irq_unlock()
is invoked in several places, therefore, we add the
barriers to make the interrupt enabling function
applicable to all usage scenarios.
Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
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