linux-kernel - Re: [RFC][PATCH 2/2] rcu classic: new algorithm for callbacks-processing(v2)

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Message-ID: <20080801211032.GT14851@linux.vnet.ibm.com>
Date:	Fri, 1 Aug 2008 14:10:32 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Lai Jiangshan <laijs@...fujitsu.com>,
	Dipankar Sarma <dipankar@...ibm.com>,
	Gautham Shenoy <ego@...ibm.com>,
	Dhaval Giani <dhaval@...ux.vnet.ibm.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH 2/2] rcu classic: new algorithm for
	callbacks-processing(v2)

On Fri, Jul 18, 2008 at 04:09:30PM +0200, Ingo Molnar wrote:
> 
> * Lai Jiangshan <laijs@...fujitsu.com> wrote:
> 
> > This is v2, it's a little deference from v1 that I
> > had send to lkml.
> > use ACCESS_ONCE
> > use rcu_batch_after/rcu_batch_before for batch # comparison.
> > 
> > rcutorture test result:
> > (hotplugs: do cpu-online/offline once per second)
> > 
> > No CONFIG_NO_HZ:           OK, 12hours
> > No CONFIG_NO_HZ, hotplugs: OK, 12hours
> > CONFIG_NO_HZ=y:            OK, 24hours
> > CONFIG_NO_HZ=y, hotplugs:  Failed.
> > (Failed also without my patch applied, exactly the same bug occurred,
> > http://lkml.org/lkml/2008/7/3/24)
> 
> thanks, i've applied this to tip/core/rcu - but it would be nice have an 
> ack/nak from Paul as well, before we can proceed further.

I like the general approach -- simplification is a good thing.

So, for the moment:

Acked-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

I need to do a more detailed review (e.g., the memory-barrier changes
and the incorporation of some grace-period processing into call_rcu()),
after which I will either ask for changes or give a Reviewed-by.

I need to do this more-detailed review before we ship to mainline.
(Gak, already two weeks since Jiangshan sent this!!!  My apologies!!!)

							Thanx, Paul
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