This intrinsic inserts a
DMB or equivalent instruction into the instruction stream generated by the compiler.
DMB instruction ensures the
ordering of memory accesses.
__dmb() intrinsic is also an optimization barrier. If
the target does not support the
DMB instruction, the
intrinsic behaves as an optimization barrier.
void __dmb(unsigned int
is a numeric argument indicating the scope and access type of the barrier. See ARM C Language Extensions for more information.