Re: PROBLEM: kernel BUG at mm/slab.c:3002!

[Hugh Dickins <hugh@veritas.com>]

On Tue, 10 Mar 2009, Alan D. Brunelle wrote:
> Matt Mackall wrote:
> > On Tue, 2009-03-10 at 13:29 -0400, Alan D. Brunelle wrote:
> >> Matt Mackall wrote:
> >>> On Tue, 2009-03-10 at 11:16 -0400, Alan D. Brunelle wrote:
> >>>> Running blktrace & I/O loads cause a kernel BUG at mm/slab.c:3002!.
> >>> Pid: 11346, comm: blktrace Tainted: G    B      2.6.29-rc7 #3 ProLiant
> >>> DL585 G5   
> >>>
> >>> That 'B' there indicates you've hit 'bad page' before this. That bug
> >>> seems to be strongly correlated with some form of hardware trouble.
> >>> Unfortunately, that makes everything after that point a little suspect.
> >>
> >> /If/ it were a hardware issue, that might explain the subsequent issue
> >> when I switched to SLUB instead...
> > 
> > Well it was almost certainly not a bug in SLAB itself (and your SLUB
> > test is obviously quite conclusive there). We'd have lots of reports.
> > It's probably too early to conclude it's hardware though.
> > 
> >> How does one look for "bad page reports"?
> > 
> > It'll look something like this (pasted from Google):
> > 
> >>>     kernel: Bad page state at free_hot_cold_page (in process 'beam',
> >>> page c1a95320)
> >>>     kernel: flags:0x40020118 mapping:f401adc0 mapped:0 count:0
> >>> private:0x00000000
> > 
> 
> Interestingly enough, I'm not seeing the kernel detect such things - but
> in going into the hardware server logs, a co-worker found "unrecoverable
> system errors" being detected at about the same times we're seeing the
> panics.

In 2.6.29-rc, the "B" taint should be associated with mm/page_alloc.c's
bad_page() KERN_ALERT "BUG: Bad page state in process %s  pfn:%05lx\n",
but it could also now come from mm/memory.c's print_bad_pte()
KERN_ALERT "BUG: Bad page map in process %s  pte:%08llx pmd:%08llx\n",
which replaces the old mm/rmap.c Eeeks, and some other cases too.

Hugh

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