Re: [v3 PATCH] hwrng: core - Remove add_early_randomness

Herbert Xu
2024-05-23T04:50:06Z

On Wed, May 22, 2024 at 03:53:23PM -0700, Linus Torvalds wrote:
>
> That said, looking at the code in question, there are other oddities
> going on. Even the "we found a favorite new rng" case looks rather
> strange. The thread we use - nice and asynchronous - seems to sleep
> only if the randomness source is emptied.
>
> What if you have a really good source of hw randomness? That looks
> like a busy loop to me, but hopefully I'm missing something obvious.

Yes that does look strange. So I dug up the original patch at

https://lore.kernel.org/all/20140317165012.GC1763@lst.de/

and therein lies the answer. It's relying on random.c to push back
when the amount of new entropy exceeds what it needs. IOW we will
sleep via add_hwgenerator_randomness when random.c decides that
enough is enough. In fact the rate is much less now compared to
when the patch was first applied.

Cheers,
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
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