re: SYNC - takes VERY  long complete  ( system freezes) !

Hubert Chaumette <[email protected]> Wed, 19 Apr 2017 13:12:40 +0200 (CEST)
Newsgroups org.kernel.vger.kernel-testers
Message-ID <598702296.8673.1492600360479.JavaMail.www@wwinf1p10>
> Any clue what could be the cause, or any hints that could explain ( and solve ?) this ..

Assuming the regression is 100% reproducible, your best bet is IMO to do a (git) bisect between the two kernels versions.
Regards,

Hubert Chaumette