I was running 0.12RC2, I downloaded 0.12RC3 (b1f031d) today and did a configure make (without a clean). This caused my mainnet and testnet nodes to crash within 1s. I tried to do a reindex on the mainnet node, and that did nothing (I shouldn't have). I did a "make clean", and rebuilt, now the testnet node appears okay (didn't try a reindex) however now the mainnet node crashes in minutes (but it sometimes takes a while, so I don't see it) with the following error:

Crash error:

bitcoind: sync.cpp:112: void potential_deadlock_detected(const std::pair<void*, void*>&, const LockStack&, const LockStack&): Assertion `onlyMaybeDeadlock' failed.

debug.log tail:

LoadExternalBlockFile: Processing out of order child 000000000000004f2d365bee2d14cea4cd33c238a75f5dee833048fa0f3855ac of 0000000000000004851be1a8e239bfd84b806f4e7341f09b73ffa7ffe7ea4700
2016-02-04 23:51:14 UpdateTip: new best=000000000000004f2d365bee2d14cea4cd33c238a75f5dee833048fa0f3855ac height=246847 log2_work=70.747326 tx=20743335 date=2013-07-16 11:09:45 progress=0.087758 cache=5.6MiB(7660tx)
2016-02-04 23:51:14 POTENTIAL DEADLOCK DETECTED
2016-02-04 23:51:14 Previous lock order was:
2016-02-04 23:51:14 (1) pnode->cs_vRecvMsg net.cpp:1736 (TRY)
2016-02-04 23:51:14 (2) cs_main main.cpp:296
2016-02-04 23:51:14 Current lock order is:
2016-02-04 23:51:14 pnode->cs_vSend net.cpp:1755 (TRY)
2016-02-04 23:51:14 (2) cs_main main.cpp:5345 (TRY)
2016-02-04 23:51:14 (1) pto->cs_inventory main.cpp:5445

I'm not sure if it's relevant but I also run "getblockchaininfo" every 0.5s to get the verification progress (I have a CLI progress bar). I've been considering doing a blockchain redownload, but I don't want to if it won't fix anything.