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Date: Tue, 10 Jan 2006 17:27:56 +0300
From: Oleg Nesterov <oleg@tv-sign.ru>
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To: vatsa@in.ibm.com
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>, linux-kernel@vger.kernel.org,
       Dipankar Sarma <dipankar@in.ibm.com>,
       Manfred Spraul <manfred@colorfullife.com>,
       Linus Torvalds <torvalds@osdl.org>, Andrew Morton <akpm@osdl.org>
Subject: Re: [PATCH 2/5] rcu: don't check ->donelist in __rcu_pending()
References: <43C165BC.F7C6DCF5@tv-sign.ru> <20060109185944.GB15083@us.ibm.com> <43C2C818.65238C30@tv-sign.ru> <20060109195933.GE14738@us.ibm.com> <20060110095811.GA30159@in.ibm.com>
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Srivatsa Vaddagiri wrote:
> 
> On Mon, Jan 09, 2006 at 11:59:33AM -0800, Paul E. McKenney wrote:
> > Hmmm...  So your thought is that __rcu_offline_cpu() moves nxtlist and
> > curlist, but not donelist, but then returns to rcu_offline_cpu(), which
> > might well do the tasklet_kill_immediate() before the tasklet completed
> > processing all of donelist.
> >
> > Seems plausible to me.  If true, your patch adding the following statement
> > to the ed of __rcu_offline_cpu seems like a reasonable fix:
> >
> >       rcu_move_batch(this_rdp, rdp->donelist, rdp->donetail);
> >
> > Vatsa, is there something that Oleg and I are missing?
> 
> I think this should take care of the CPU Hotplug bug, with the caveat
> that the callbacks on ->donelist will wait for additional grace period before
> being invoked (which seems ok).
> 
> Oleg, do you want to resend the patch after some testing?

Sure. The problem is that I have no idea how to test this change.
However, the patch seems "obviously correct", so I am sending it.

Srivatsa, I am sorry, I forgot to add you on CC: list while re-sending
these cleanups. I hope you can see them on lkml.

Oleg.