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SubjectRe: unaligned accesses in SLAB etc.
> From: David Miller <davem@davemloft.net>
> Date: Sat, 11 Oct 2014 22:15:10 -0400 (EDT)
>
> >
> > I'm getting tons of the following on sparc64:
> >
> > [603965.383447] Kernel unaligned access at TPC[546b58] free_block+0x98/0x1a0
> > [603965.396987] Kernel unaligned access at TPC[546b60] free_block+0xa0/0x1a0
> > [603965.410523] Kernel unaligned access at TPC[546b58] free_block+0x98/0x1a0

> In all of the cases, the address is 4-byte aligned but not 8-byte
> aligned. And they are vmalloc addresses.
>
> Which made me suspect the percpu commit:
>
> ====================
> commit bf0dea23a9c094ae869a88bb694fbe966671bf6d
> Author: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> Date: Thu Oct 9 15:26:27 2014 -0700
>
> mm/slab: use percpu allocator for cpu cache
> ====================
>
> And indeed, reverting this commit fixes the problem.

I tested Joonsoo Kim's fix and it gets rid of the kernel unaligned
access messages, yes.

But the instability on UltraSparc II era machines still remains -
occassional Bus Errors during kernel compilation, messages like this:

sh[11771]: segfault at ffd6a4d1 ip 00000000f7cc5714 (rpc 00000000f7cc562c) sp 00000000ffd69d90 error 30002 in libc-2.19.so[f7c44000+16a000]

--
Meelis Roos (mroos@linux.ee)


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