[Crash-utility] Re: Question about fixing another crash annoyance...t

[Dave Anderson]

----- "Bob Montgomery" <bob.montgomery at hp.com> wrote:
> 
> Dave,
> 
> You are faster than me at fixing crash:-)  I was just about to start on
> the part for kmem_cache_len_nodes...
> 
> The patch fixes the problem on my example dump which previously said:
> =====
> please wait... (gathering kmem slab cache data)
> crash: page excluded: kernel virtual address: ffff88022457a000  type:
> "kmem_cache_s buffer"
> 
> crash: unable to initialize kmem slab cache subsystem
> =====
> 
> It now says:
> =====
> please wait... (gathering kmem slab cache data)
> kmem_cache_downsize: SIZE(kmem_cache_s): 872 cache_cache.buffer_size: 384
> kmem_cache_downsize: nr_node_ids: 2
> =====
> 

Sorry -- I didn't mean to leave the "CRASHDEBUG(0)" in there, so the
messages above shouldn't normally be displayed.  I'll make it
CRASHDEBUG(1) so we'll have a record of it happening if something
else comes up in the future.

> 
> In the meantime, I remembered "--zero_exclude", which makes for
> a slightly dangerous workaround for the problem.  It fills in the
> unnecessarily-accessed missing pages with zeros.
>
> The output of "kmem -s" and "kmem -S" on my problem dump is the
> same between your patched version and the old version running 
> with --zero_exclude.  (I don't normally think of using zero_exclude
> because it can mask both kernel bugs and makedumpfile bugs...)

Yep --zero_excluded masks this problem quite nicely... ;-)

> Thanks for making that patch.  Is there anything left to
> fix in crash ?-)

No doubt...

Thanks,
  Dave