linux-kernel - Re: [PATCH -tip] v9 scalable classic RCU implementation

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Message-ID: <20081219014946.GJ6912@linux.vnet.ibm.com>
Date:	Thu, 18 Dec 2008 17:49:46 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	linux-kernel@...r.kernel.org, cl@...ux-foundation.org,
	mingo@...e.hu, akpm@...ux-foundation.org, manfred@...orfullife.com,
	dipankar@...ibm.com, josht@...ux.vnet.ibm.com, schamp@....com,
	niv@...ibm.com, dvhltc@...ibm.com, ego@...ibm.com,
	laijs@...fujitsu.com, rostedt@...dmis.org, peterz@...radead.org,
	penberg@...helsinki.fi, tglx@...utronix.de
Subject: Re: [PATCH -tip] v9 scalable classic RCU implementation

On Fri, Dec 19, 2008 at 02:29:35AM +0100, Andi Kleen wrote:
> On Thu, Dec 18, 2008 at 02:54:03PM -0800, Paul E. McKenney wrote:
> > On Tue, Dec 02, 2008 at 05:36:59PM -0800, Paul E. McKenney wrote:
> > > On Wed, Dec 03, 2008 at 02:10:42AM +0100, Andi Kleen wrote:
> > > > > On Power, I see a hang in all three flavors of RCU when CPU hotplug
> > > > > is enabled and dynticks is not.  I have not yet seen this hang on x86.
> > > > > On Power, the hang occurs in the CPU-offline code, and is identical to
> > > > > the hangs I was seeing in 2.6.27, except that "sleep 1" does not hang
> > > > > in recent 2.6.28 versions.  So the timeout is apparently failing to fire
> > > > > (or being ignored) for some other reason.
> > > > > 
> > > > > Is this similar to what you are seeing on x86?
> > > > 
> > > > Yes it is.
> > > 
> > > OK, then I will consider them to be the same bug for the moment.
> > 
> > Question based on some further testing over here...
> > 
> > Do you still get failures if you refrain from offlining CPU 0?
> 
> Yes, i never offlined cpu 0 in fact.

Hmmm...  Then you are most likely seeing a different failure than I see
on Power.

Could you please retry with v10 of the patch, setting CONFIG_TREE_RCU?

							Thanx, Paul
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