Hi Thomas, On Mon, Apr 25, 2022 at 02:37:11PM +0200, Thomas Gleixner wrote: > On Sat, Apr 23 2022 at 23:26, Jason A. Donenfeld wrote: > > The addition of random_get_entropy_fallback() provides access to > > whichever time source has the highest frequency, which is useful for > > gathering entropy on platforms without available cycle counters. It's > > not necessarily as good as being able to quickly access a cycle counter > > that the CPU has, but it's still something, even when it falls back to > > being jiffies-based. > > > > In the event that a given arch does not define get_cycles(), falling > > back to the get_cycles() default implementation that returns 0 is really > > not the best we can do. Instead, at least calling > > random_get_entropy_fallback() would be preferable, because that always > > needs to return _something_, even falling back to jiffies eventually. > > It's not as though random_get_entropy_fallback() is super high precision > > or guaranteed to be entropic, but basically anything that's not zero all > > the time is better than returning zero all the time. > > > > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > > Cc: Arnd Bergmann <arnd@xxxxxxxx> > > Cc: Theodore Ts'o <tytso@xxxxxxx> > > Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx> > > Not that I care much, but in general taking over authorship w/o > attribution via Suggested-by or such is frowned upon. Sorry about that. Usually I'm pretty good about adding those. I guess something must have gotten lost this time through, as the v1 of this started out using sched_clock() (Arnd's suggestion) and then moved to using the raw ktime clock after your suggestion, and I missed the Suggested-by. I'll add that. Meanwhile, do you want to Ack this patch? Do the technical aspects look okay to you? Jason
