git bisect bad master <- mark "master" as the bad state
git bisect good ORIG_HEAD <- mark ORIG_HEAD as good (or
whatever other known-good
- thing you booted laste)
+ thing you booted last)
and at this point "git bisect" will churn for a while, and tell you what
the mid-point between those two commits are, and check that state out as
-the head of the bew "bisect" branch.
+the head of the new "bisect" branch.
Compile and reboot.