hs_try_putmvar003 is timing out / segfaulting

This is basically reproduceable every time I validate. During validation, the program times out, but when I run it by hand, it segfaults. Running in debug sanity mode, I get:

hstry: internal error: MVAR_CLEAN on mutable list
    (GHC version 8.3.20170316 for x86_64_unknown_linux)
    Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

Simon Marlow, I'm happy to investigate more if you can't repro.

Trac metadata

Trac field	Value
Version	8.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Runtime System
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	simonmar
Operating system
Architecture

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information

Admin message

hs_try_putmvar003 is timing out / segfaulting