I have a test-case that could easily provoke a deadlock described in thishttps://bugs.freebsd.org/bugzilla/show_bug.cgi?id=215972#c11
bug report: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=215972#c11on Phenom II X6 1090T.
After this change the deadlock is no longer reproducible.
I haven't seen any regressions so far.