On Fri, Jun 16, 2017 at 4:35 PM, Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> wrote: > I wouldn't just push the lock one up as is but move that write part to > crng_init to remain within the locked section. Like that: We can't quite do that, because invalidate_batched_entropy() needs to be called _before_ crng_init. Otherwise a concurrent call to get_random_u32/u64() will have crng_init being the wrong value when the batched entropy is still old. > Are use about that? I am not sure that the gcc will inline "crng_init" > read twice. It is not a local variable. READ_ONCE() is usually used > where gcc could cache a memory access but you do not want this. But hey! > If someone knows better I am here to learn. The whole purpose is that I _want_ it to cache the memory access so that it is _not_ inlined. So, based on your understanding, it does exactly what I intended it to do. The reason is that I'd like to avoid a lock imbalance, which could happen if the read is inlined. Jason
