Messages in this thread | | | Date | Fri, 18 Dec 2009 15:04:43 -0500 | From | Mark Hounschell <> | Subject | Re: [Fdutils] DMA cache consistency bug introduced in 2.6.28 (Was: Re: Cannot format floppies under kernel 2.6.*?) |
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On 12/18/2009 10:45 AM, Linus Torvalds wrote: > > > On Fri, 18 Dec 2009, Mark Hounschell wrote: >> >> Yep, thanks. I'm past that now. But haven't done a bisect [good|bad] on the >> results of that one yet. Did you see Alain's email response to my bisect >> progress report to him? >> >> I'm still at a loss as to how to proceed? > > Ahh, the HPET issue. > > That one is actually very interesting information, because we've had > problems with HPET before. But what I would suggest is to try to continue > to bisect with HPET enabled (to see the problem), and the commit that you > couldn't even boot with HPET enabled you should not count as good or bad > because you just don't know. > > You can do "git bisect skip" to make git know that some particular commit > is not a commit you can test, and you can also move away from a whole > problematic region to another area by doing > > git bisect visualize > > to bring up a graphical gitk view of what all you have left to bisect, > pick a good point (still _reasonably_ close to the middle) there, and do > > git reset --hard <the-point-you-want-to-test> > > and try that kernel instead of the one git bisect suggested. > > But this floppy DMA inconsistency being somehow HPET-related is > interestign in itself. One thing that HPET does si to obviously change how > we read the time - and what that can cause (totally indirectly) is that > now we don't touch the southbridge with IO accesses nearly as much, > because instead of going to the old 8253 PIT will touch the same legacy > chip support that implements the floppy controller itself. > > So it's entirely possible that the reason a non-HPET setup doesn't show > this is that the accesses to the i8253 PIT part will "synchronize" the old > floppy controller too, and hide some issue. > > But still, I assume you had HPET enabled in 2.6.27, so it would be > interesting to see exactly when the problem starts. > > Linus >
It looks like I may have to back up and first find the points that, let me, and stop me, booting with the HPET enabled. Before I change direction, can the git-bisect start sequence use the SHA1 id for the starting 'goods' and 'bads'? I don't see reference to that in the doc.
Thanks Mark
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