Ok, I suspect it may be timing-dependent and slightly random.
Sadly, that is absolutely the case where "git bisect" works the worst. The
end result of bisection will basically be _totally_ random if even one of
the "git bisect bad/good" choises were wrong - doing a binary search is
a very efficient way to find the buggy commit, but it also means that a
single wrong turn will efficiently find a commit that is somewhere totally
different.
So if your shutdown/reboot regression is even slightly non-deterministic,
it makes "git bisect" rather less powerful (you can still do bisection,
but you just need to be extra careful and probably try multiple shutdowns
with a suspect kernel just to be absolutely sure you mark a kernel good
only if you're *really* sure it's good. Marking a kernel bad is much
safer, since you'd presumably only do that when you have actually seen the
bug in action)..
Of course, even when you're really really careful, if it really is
timing-dependent, the bug may show up with a unrelated commit just because
it changes timing. Those kinds of bugs tend to be fairly rare, but they do
occasionally happen.
Linus
--
