linux-kernel - Re: [RFC][PATCH] slub: Check for page NULL before doing the node

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Date:	Thu, 17 Jan 2013 17:10:47 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Christoph Lameter <cl@...ux.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Pekka Enberg <penberg@...nel.org>,
	Matt Mackall <mpm@...enic.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	RT <linux-rt-users@...r.kernel.org>,
	Clark Williams <clark@...hat.com>,
	John Kacur <jkacur@...il.com>,
	"Luis Claudio R. Goncalves" <lgoncalv@...hat.com>
Subject: Re: [RFC][PATCH] slub: Check for page NULL before doing the
 node_match check

On Thu, 2013-01-17 at 21:56 +0000, Christoph Lameter wrote:
> on Thu, 17 Jan 2013, Christoph Lameter wrote:
> 
> > Ditto which leaves us with:
> >
> > Index: linux/mm/slub.c
> > ===================================================================
> > --- linux.orig/mm/slub.c	2013-01-17 15:49:57.417491975 -0600
> > +++ linux/mm/slub.c	2013-01-17 15:50:49.010287150 -0600
> > @@ -1993,8 +1993,9 @@ static inline void flush_slab(struct kme
> >  	deactivate_slab(s, c->page, c->freelist);
> >
> >  	c->tid = next_tid(c->tid);
> > -	c->page = NULL;
> >  	c->freelist = NULL;
> > +	barrier();
> > +	c->page = NULL;
> >  }
> 
> But the larger question is why is flush_slab() called with interrupts
> enabled?
> 
> RT?

Could be, there's a few tweaks made in -rt. I'll put in a WARN_ON_ONCE()
if flush_slab() is called with interrupts enabled just to see where it
happens.

-- Steve


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