runtime: lock ordering problem between sweep and mspanSpecial

[bcmills]

0 : sweep 7 0x663320
1 : mspanSpecial 22 0x7fd5af0f7418
fatal error: lock ordering problem

2020-11-09T19:46:24-a2d0147/linux-amd64-staticlockranking
2020-10-31T08:31:08-12a2e72/linux-amd64-staticlockranking
2020-10-23T20:53:14-d1b1145/linux-amd64-staticlockranking

CC @danscales @mknyszek

[mknyszek]

This is a missing partial edge. It's definitely a correct ordering: this is the background sweeper queuing a finalizer or handling a memory profile sample.

[gopherbot]

Change https://golang.org/cl/268857 mentions this issue: runtime: add lock rank partial order edge sweep -> mspanSpecial