Re: [PATCH v6 0/5] /dev/random - a new approach

[Herbert Xu]

On Fri, Aug 19, 2016 at 10:20:18AM -0700, H. Peter Anvin wrote:
> On 08/18/16 22:56, Herbert Xu wrote:
> > On Thu, Aug 18, 2016 at 10:49:47PM -0400, Theodore Ts'o wrote:
> >>
> >> That really depends on the system.  We can't assume that people are
> >> using systems with a 100Hz clock interrupt.  More often than not
> >> people are using tickless kernels these days.  That's actually the
> >> problem with changing /dev/urandom to block until things are
> >> initialized.
> > 
> > Couldn't we disable tickless until urandom has been seeded? In fact
> > perhaps we should accelerate the timer interrupt rate until it has
> > been seeded?
> > 
> 
> The biggest problem there is that the timer interrupt adds *no* entropy
> unless there is a source of asynchronicity in the system.  On PCs,
> traditionally the timer has been run from a completely different crystal
> (14.31818 MHz) than the CPU, which is the ideal situation, but if they
> are run off the same crystal and run in lockstep, there is very little
> if anything there.  On some systems, the timer may even *be* the only
> source of time, and the entropy truly is zero.

Sure, but that's orthorgonal to what Ted was talking about above.

Thanks,
-- 
Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
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