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List:       linux-kernel
Subject:    Re: 2.3.12 - klogd 100% CPU && Bogus Buffer memory count
From:       Mofeed Shahin <shahin () labf ! org>
Date:       1999-08-10 8:57:03
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Well Chuck, I have just tried using the same cd again and yes it is
reproducable.
As soon as I get one of these :

Aug 10 18:16:26 tt2 kernel: attempt to access beyond end of device 
Aug 10 18:16:26 tt2 kernel: 0b:00, want=532574, limit=532572 

klogd starts using 100% CPU.

So it looks like the race condition is in the cdrom layer.

Anything else I can do to try find this bug, I will be happy to do.

Cheers Mof.


On Fri, 6 Aug 1999, Chuck Lever wrote:

> mofeed-
> 
> there's a race somewhere that's causing shrink_mmap to deduct too much
> from buffermem, making it go negative.  i don't think that it's specific
> to a particular driver.  i haven't been able to simply and consistently
> reproduce the race -- maybe you could come up with some way to do this?
> is it specific to how much data you copied, for instance?
> 
> On Fri, 6 Aug 1999, Mofeed Shahin wrote:
> > First off I will explain what I was doing that caused the problem.
> > I was copying a whole CD to the hard-drive. They are both scsi AIC7xxx.
> > 
> > While I was copying I noticed Xosview not looking too healthy so I ran top
> > and noticed that the amount of buffer memory was obviously wrong.
> > 
> > here is the vmstat output :
> > 
> > :vmstat
> >    procs                      memory    swap          io     system cpu
> >  r  b  w   swpd   free   buff  cache  si  so    bi    bo   in    cs  us sy id
> >  1  0  0    744   2908 4193304 205452   0   0     2     4   52    14  47 0 53
> >                        ^^^^^^^
> > Notice the 4.1 GIG of buffer memory.
> > 
> > Also half way through the copy klogd started using up all the CPU time on
> > one of the processors.
> > Even after the copy had finished klogd was still using up large amounts of
> > CPU (100%).
> 
> 	- Chuck Lever
> --
> corporate:	<chuckl@netscape.com>
> personal:	<chucklever@netscape.net> or <cel@monkey.org>
> 
> The Linux Scalability project:
> 	http://www.citi.umich.edu/projects/linux-scalability/
> 


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