netdev - Re: [PATCH] net: fib: fix incorrect call_rcu

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Message-ID: <1344358094.28967.116.camel@edumazet-glaptop>
Date:	Tue, 07 Aug 2012 18:48:14 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	paulmck@...ux.vnet.ibm.com
Cc:	David Miller <davem@...emloft.net>, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] net: fib: fix incorrect call_rcu_bh()

On Tue, 2012-08-07 at 09:34 -0700, Paul E. McKenney wrote:
> On Tue, Aug 07, 2012 at 12:47:11PM +0200, Eric Dumazet wrote:
> > From: Eric Dumazet <edumazet@...gle.com>
> > 
> > After IP route cache removal, I believe rcu_bh() has very little use and
> > we should remove this RCU variant, since it adds some cycles in fast
> > path.
> 
> Do you mean remove all uses of RCU-bh globally and also removing the
> implementation itself?  That would actually be a good thing, from my
> perspective.
> 

Yes I meant that there are now too few rcu_bh users, and that they
probably could switch to regular rcu.

We could then remove the implementation.

rcu_bh was needed because we could sit forever in softirq mode in one
cpu, and we needed to allocate/free dsts with RCU protection.



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