Messages in this thread | | | Subject | Re: Regression in kernel 4.12-rc1 for Powerpc 32 - bisected to commit 3448890c32c3 | From | Larry Finger <> | Date | Fri, 23 Jun 2017 13:49:16 -0500 |
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On 06/22/2017 02:25 PM, Al Viro wrote: > On Thu, Jun 22, 2017 at 09:19:58AM -0500, Larry Finger wrote: > >>> Ugh... MintPPC appears to be dead. On KVM with Debian userland (either >>> jessie or wheezy - no difference in result) booting the commit in >>> question with your .config oopses as soon as pata_macio is initialized, >>> due to the bug in "treewide: Move dma_ops from struct dev_archdata into >>> struct device", and after cherry-picking your own fix for that (commit >>> 46f401c4297a "powerpc/pmac: Fix crash in dma-mapping.h with NULL dma_ops") >>> the result boots just fine. >>> >>> Again, that happens both for Debian 8 and Debian 7 userlands, so unless >>> Mint had been doing something very odd there, I would question the accuracy >>> of your bisect... > >> Any chance that real hardware differs from KVM emulation? > > For that one? Bloody unlikely; udev could, theoretically, hit different codepaths > due to different devices being observed, etc., but changes in that commit are > not in the areas that would be easy to get wrong in emulator. > >> All I know at this >> point is that commit f2ed8beb with 46f401c4 backported boots OK and commit >> 3448890c with the same backport fails. >> >> I will try loading jessie and see what happens. > > I would recheck which kernels are being booted - I had screwed that up during long > bisects often enough... > > BTW, could you try to check what happens if you kill the > if (__builtin_constant_p(n) && (n <= 8)) > bits in raw_copy_{to,from}_user()? The usefulness of those (in __copy_from_user() > originally) had always been dubious and the things are simpler without them. > If _that_ turns out to cure breakage, I would be very surprised, though. > Sorry I was gone so long. Installing jessie on this box resulted in a crash on boot. Lubuntu 14.04 yielded a desktop with a functioning cursor, but nothing else. Finally, Ubuntu 12.04 resulted in a working system. I hate Unity, but I guess I'm stuck for now.
I know how easy it is to screw up a long bisection by booting the wrong kernel. To help that problem and to work around the yaconf/yboot nonsense on the MAC, my /etc/yaconf has always had generic kernel stanzas with only default, old, and original kernels mentioned. From there I use a local script to finish a kernel installation by moving the default links to the old ones and creating the new default links pointing to the current kernel. With those long-tested scripts, I'm sure that I am booting the one I want.
With the new installation, kernel 4.12-rc6 failed, as did 3448890c with the backported 46f401c4 added.
Replacing "if (__builtin_constant_p(n) && (n <= 8))" with "if (0)" had no effect.
Larry
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