set_bit — Atomically set a bit in memory
void set_bit (int nr, volatile unsigned long * addr);
This function is atomic and may not be reordered. See __set_bit
if you do not require the atomic guarantees.
there are no guarantees that this function will not be reordered on non x86 architectures, so if you are writting portable code, make sure not to rely on its reordering guarantees.
Note that nr may be almost arbitrarily large; this function is not
restricted to acting on a single-word quantity.