linux-kernel - Re: [PATCH V4 1/1] rcu: introduce kfree

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Message-ID: <20110316040308.GC2273@linux.vnet.ibm.com>
Date:	Tue, 15 Mar 2011 21:03:08 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Lai Jiangshan <laijs@...fujitsu.com>, Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>,
	Manfred Spraul <manfred@...orfullife.com>
Subject: Re: [PATCH V4 1/1] rcu: introduce kfree_rcu()

On Tue, Mar 15, 2011 at 02:11:33PM +0100, Eric Dumazet wrote:
> Le mardi 15 mars 2011 à 17:46 +0800, Lai Jiangshan a écrit :
> 
> 
> > --- a/kernel/rcutiny.c
> > +++ b/kernel/rcutiny.c
> > @@ -167,7 +167,7 @@ static void rcu_process_callbacks(struct rcu_ctrlblk *rcp)
> >  		prefetch(next);
> >  		debug_rcu_head_unqueue(list);
> >  		local_bh_disable();
> > -		list->func(list);
> > +		__rcu_reclaim(list);
> >  		local_bh_enable();
> >  		list = next;
> >  		RCU_TRACE(cb_count++);
> 
> Paul, I am just wondering why we disable BH before calling list->func()
> 
> This should be done in callbacks that really need it ?
> 
> At least the disable/enable pair is not necessary before calling kfree()

Good point, we could bury the enable/disable pair in __rcu_reclaim().

Lai, am I forgetting any reason why we disable BH?

							Thanx, Paul
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