Re: locking against myself panic (cprng_strongreseed, filt_rndread)

[Taylor R Campbell <campbell+netbsd-tech-kern%mumble.net@localhost>]

> Date: Tue, 7 Nov 2017 22:58:39 +0100
> From: Edgar =?iso-8859-1?B?RnXf?= <ef%math.uni-bonn.de@localhost>
> 
> I got the following panic on a mostly idle 6.1/amd64:
> 
> Mutex error: mutex_vector_enter: locking against myself
> [...]
> mutex_vector_enter() at netbsd:mutex_vector_enter+0x3df
> filt_rndread() at netbsd:filt_rndread+0x16
> knote() at netbsd:knote+0x33
> selnotify() at netbsd:selnotify+0x24
> cprng_strong_doreseed() at netbsd:cprng_strong_doreseed+0xbd
> cprng_strong_reseed() at netbsd:cprng_strong_reseed+0x2d
> rnd_wakeup_readers() at netbsd:rnd_wakeup_readers+0x171
> callout_softclock() at netbsd:callout_softclock+0x174

Not surprising: cprng locking was completely hosed in netbsd-6 until
it got rewritten for netbsd-7.  If this is particularly important, we
can maybe find a way to pull up a simpler change to netbsd-6, or pull
up all of the netbsd-7 entropy subsystem wholesale, but it may not be
easy either way.