On Mon, Dec 23, 2019 at 6:31 AM Christophe Leroy
[off-list ref] wrote:

READ_ONCE() forces the read of the 64 bit value of
vd[CS_HRES_COARSE].basetime[CLOCK_REALTIME].sec allthough
only the lower part is needed.

Seems reasonable and very unlikely to be harmful.  That being said,
this function really ought to be considered deprecated -- 32-bit
time_t is insufficient.

Do you get even better code if you move the read into the if statement?

Reviewed-by: Andy Lutomirski <luto@kernel.org>

--Andy