Re: Logging a kernel message when blocking on entropy

[Paul Goyette <paul%whooppee.com@localhost>]

On Tue, 22 Sep 2020, Taylor R Campbell wrote:

> > Date: Tue, 22 Sep 2020 13:07:04 +0300
> > From: Andreas Gustafsson <gson%gson.org@localhost>
> >
> > The following patch will cause a kernel message to be logged when a
> > process blocks on /dev/random or some other randomness API.  It may
> > help some users befuddled by pkgsrc builds blocking on /dev/random,
> > and I'm finding it useful when testing changes aimed at fixing PR
> > 55659.
> >
> > OK to commit?
>
> I think this is fine, but it should be rate-limited the same way other
> messages in kern_entropy.c are rate-limited.
>
> 		if (ratecheck(&lasttime, &interval))
> 			printf("...");

Not sure if that's really necessary.  There's a maximum of one message
per thread - ever, and even if every thread on the machine blocks, the
limit on number of threads stops you at 32k messages.  As soon as one
thread un-blocks, nothing will ever block again, so that feels like a
hard limit.

Of course, since the rate-limiting code is already written, it wouldn't
hurt to use it.  I'm just pointing out that there's a natural limit
inherent in the code!

:)


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