On Fri, Sep 04, 2009 at 04:56:21PM +0100, Richard Smith wrote:
> Within my UML guest kernel, I'm finding that between 5% and 
> 10% of reads from /dev/hwrng block, seemingly indefinitely. 
> (I've certainly seem reads block for more than 12 hours.) 
> All other reads complete in significantly less than 1 
> second.

Make sure that the host has entropy.  hwrng relies on that, and will
block until the host can fork over some bits.

> I.e. we appear to be blocking in the host 
> kernel.  My obvious first thought is that the host kernel's 
> entropy is depleted, although it seems hard to believe that 
> this could explain the guest blocking for 12+ hours.
> 
> The host is running rngd which seems to be effective at 
> preventing the UML guests from depleting the host kernel's 
> entropy pool.  If I monitor the available host entropy, I 
> see:

Can you actually dd bits out of the host's /dev/random?

                        Jeff

-- 
Work email - jdike at linux dot intel dot com

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