Reproducible "calcru: negative time ..." on SMP system

I discovered that on a 5.2-BETA SMP system I can cause

Feb  8 18:29:32 <kern.crit> bento kernel: calcru: negative time of 6816 usec for pid 50286 (grep)
Feb  8 18:29:41 <kern.crit> bento kernel: calcru: negative time of 7308 usec for pid 51007 (grep)
Feb  8 18:30:41 <kern.crit> bento kernel: calcru: negative time of 6104 usec for pid 54944 (grep)
Feb  8 18:30:42 <kern.crit> bento kernel: calcru: negative time of 5933 usec for pid 54962 (grep)

by running a shell script that does lots of greps, and leaning on the
^T key in the shell to send the process lots of SIGINFOs.

Kris