Re: [BUG] 2.6.3 Slab corruption: errors are triggered when memoryexceeds 2.5GB (correction)

[Manfred Spraul]

Darren Williams wrote:

> Hi Manfred
>
> I have updated to the latest bk and new output can be found at:
> http://quasar.cse.unsw.edu.au/~dsw/public-files/lemon-debug/
> kern-log-bk
>
> Also I am quite confident that it is not a hardware problem.
>
> I took a look at alloc_skb(..) and there is a reference to
> an atomic_t token with this being the most suspect
>
> 150> atomic_set(&(skb_shinfo(skb)->dataref), 1);
>  
I don't think so:
The allocation that generates the error is skb->head: The cache name is 
"size-2048", thus the allocation is a kmalloc(1000-2000, probably 1536 
for one eth frame). The skb itself is allocated from the skbuff_head_cache.

I don't see a pattern in the virtual addresses:
start=e000000101ee09a0, len=2048
start=e000000101ee09a0, len=2048
start=e000000101ee11b8, len=2048
start=e000000101ee19d0, len=2048
start=e000000101ee3218, len=2048
start=e00000017eed1b90, len=2048
start=e00000017eed23a8, len=2048
start=e00000017eed2bc0, len=2048
start=e00000017eed4308, len=2048
start=e00000017eed5338, len=2048
start=e00000017eed5338, len=2048
start=e00000017eed5b50, len=2048
start=e00000017eed5b50, len=2048
start=e00000017eed6b80, len=2048
start=e00000017eed82c8, len=2048
start=e00000017eedc288, len=2048
start=e00000017eedcaa0, len=2048
start=e00000017eeddad0, len=2048
start=e00000017eede2e8, len=2048
start=e00000017eedeb00, len=2048
start=e00000017ef60a60, len=2048
start=e00000017ef61a90, len=2048
start=e00000017ef622a8, len=2048
start=e00000017ef62ac0, len=2048
start=e00000017ef632d8, len=2048
start=e00000017ef65a50, len=2048
start=e00000017ef65a50, len=2048
start=e00000017ef65a50, len=2048
start=e00000017ef66a80, len=2048

That virtually rules out a bad memory chip.

But the corrupted byte is always at offset 0x620 into the allocation:
Slab corruption: start=e00000017ef65a50, len=2048
620: 6a 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
--
Slab corruption: start=e000000101ee19d0, len=2048
620: 6a 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
--
Slab corruption: start=e000000101ee3218, len=2048
620: 6a 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
--
Slab corruption: start=e00000017ef66a80, len=2048
620: 6a 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
--
Slab corruption: start=e000000101ee11b8, len=2048
620: 6a 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b

0x620 (1568) is behind the end of the actual eth frame. Who could modify 
that?

Darren, which nic do you use? Could you try what happens if you reduce 
the MTU?

--
   Manfred

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