Red Hat Bugzilla – Bug 448598
CONFIG_DEBUG_PAGEALLOC doesn't work on ppc32
Last modified: 2013-01-09 22:20:16 EST
I'm getting oopses from the kernel on a ppc mac mini with rawhide kernel.
Fedora 9 installs and runs fine, it's only after rebooting to the rawhide kernel
that I start getting oopses. I've attached a photo from the screen, I can get
more if necessary.
Created attachment 306824 [details]
Photo of oops
This only just started happening because I turned on PAGEALLOC_DEBUG for all archs.
There was an exception in the ppc config disabling this, which meant that it
never got tested during F9 development at all.
Looking at the oops, I'm wondering if this feature is just busted on PPC, and
that's why it was explicitly disabled, rather than inheriting the setting from
Created attachment 306826 [details]
Another oops with selinux=0
I was asked to boot with selinux=0 and I got farther.
Added Ben to CC. Perhaps he can decipher some of the mysticism behind why
PAGEALLOC_DEBUG wasn't set in the past.
Created attachment 306871 [details]
powerpc32 UP config
This should be the .config file that is used with the rawhide kernels.
I'll have a look tomorrow. In the meantime, fedora should disable it for 32 bits
powerpc (64 bits should be allright). Appart from the problem reported, there
are known issues with DEBUG_PAGEALLOC on ppc32 SMP for example. I have some
plans to fix that but in the meantime, it's probably better to disable the whole
Disabled on ppc32 for now.
Per comment #7. Is this bug resolved?
This bug has been triaged
John, upstream is still broken, but when we enabled this option during development we explicitly disabled it on ppc32. It's likely we'll do the same thing when F11 opens up for devel, and continue doing so until upstream supports DEBUG_PAGEALLOC
Dave: that's probably the way to go. It's going to take time to fix that one, because of the way ppc32 "classic MMU" works. We map the kernel linear mapping using a specific CPU facility to create huge fixed mappings that is fundamentally incompatible with DEBUG_PAGEALLOC, and we have some areas where the code assumes that mapping (ie, it assumes it cannot take an MMU hash miss) on linear mapping accesses. It's possible to "fix" but tricky and nobody so far had time to work on it.
This bug appears to have been reported against 'rawhide' during the Fedora 10 development cycle.
Changing version to '10'.
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