Re: rc5 seemed to kill a disk that rc4-mm1 likes. Also some X trouble.

[Linus Torvalds <torvalds@osdl.org>]

On Mon, 5 Sep 2005, Rolf Eike Beer wrote:
> 
> The problem appeared between 2.6.12-git3 and 2.6.12-git4.

Just for reference, that's git ID's

 1d345dac1f30af1cd9f3a1faa12f9f18f17f236e..2a5a68b840cbab31baab2d9b2e1e6de3b289ae1e

and that's 225 commits and the diff is 55,781 lines long.

It would be very good if you could try to use raw git and narrow it down a 
bit more. It's really easy these days with a recent git version, just do

	git bisect start
	git bisect good 1d345dac1f30af1cd9f3a1faa12f9f18f17f236e
	git bisect bad 2a5a68b840cbab31baab2d9b2e1e6de3b289ae1e

and off you go.. That will select a new kernel for you to try, which
basically cuts down the commits to ~110 - and if you can test just a few 
kernels and binary-search a bit more, we'd have it down to just a couple.

If you want to try work smarter (rather than a brute-force binary search 
thing), this command line:

  git-whatchanged -p \
	1d345dac1f30af1cd9f3a1faa12f9f18f17f236e..2a5a68b840cbab31baab2d9b2e1e6de3b289ae1e \
	drivers/video

will actually give you some very good information on what to try (I forget 
your exact original problem - I'm writing this from Italy, and I don't 
have my full email archives here. It was some MGA card that stopped 
working, no? Or was there something else?).

Anyway, git users really have a lot of nifty tools to help chase down bugs
like this. I used that "git bisect" thing twice myself last week. And the
"git-whatchanged" thing really is pretty flexible: as you can see, you can
limit it to both a range of commits and a certain subdirectory (or a _set_
of subdirectories and/or individual files - you can have as many pathname
limits as you want).

And that "-p" thing makes it show the whole diff for the thing (replace if
with a "-s" if you just want to see the descriptions and be silent about 
the actual diff).

All in my never-ending quest to make people more aware of how they can use 
git to pinpoint the source of kernel bugs.

		Linus
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