linux-kernel - Re: [PATCH] Fix WARN_ON / WARN_ON

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Date:	Thu, 05 Oct 2006 14:01:46 -0700
From:	Tim Chen <tim.c.chen@...ux.intel.com>
To:	andrew.j.wade@...il.com
Cc:	Andrew Morton <akpm@...l.org>, herbert@...dor.apana.org.au,
	linux-kernel@...r.kernel.org, leonid.i.ananiev@...el.com
Subject: Re: [PATCH] Fix WARN_ON / WARN_ON_ONCE regression



On Thu, 2006-10-05 at 17:31 -0400, Andrew James Wade wrote:
> On Thursday 05 October 2006 04:36, Andrew Morton wrote:
> > On Thu, 5 Oct 2006 04:13:07 -0400
> > Andrew James Wade <andrew.j.wade@...il.com> wrote:
> > 
> > > (...)
> > 
> > 
> > That all looks OK (by sheer luck).
> > 
> > Well.  What's the cache line size on that machine?  Every exit() will cause
> > a down_read() on task_exit_notifier's lock which might affect things.  And
> > I think you snipped the above list a bit short (depending on that line
> > size).
> > 
> > 
> > But still, we know that moving those things into __read_mostly didn't fix
> > it, yes?
> 
> No. To my knowledge Tim Chen hasn't tried __read_mostly, and I have not
> attempted to replicate the test case. (I only have a uniprocessor
> machine.) Core 2 machines have a cache line size of 64 bytes, but Tim
> Chen is likely using a different kernel/.config than I am so my objdump
> isn't definitive.
> 
> Tim, perhaps you can try the __read_mostly marking as Andrew suggests?
> 

I have run the workload with __read_mostly marking.  But it didn't make
a difference.  By the way, the cache line size of my machine is 64
bytes.

Thanks.

Tim
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