From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: [PATCH 3/8] net: Add Generic Receive Offload infrastructure Date: Mon, 15 Dec 2008 16:02:01 -0800 Message-ID: <20081216000201.GG6759@linux.vnet.ibm.com> References: <20081213013420.GA13549@gondor.apana.org.au> <20081215232942.GD6759@linux.vnet.ibm.com> <20081215.153920.105386030.davem@davemloft.net> Reply-To: paulmck@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: herbert@gondor.apana.org.au, netdev@vger.kernel.org, johnpol@2ka.mipt.ru, bhutchings@solarflare.com To: David Miller Return-path: Received: from e4.ny.us.ibm.com ([32.97.182.144]:56497 "EHLO e4.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753565AbYLPACD (ORCPT ); Mon, 15 Dec 2008 19:02:03 -0500 Received: from d01relay02.pok.ibm.com (d01relay02.pok.ibm.com [9.56.227.234]) by e4.ny.us.ibm.com (8.13.1/8.13.1) with ESMTP id mBG01HmI025901 for ; Mon, 15 Dec 2008 19:01:17 -0500 Received: from d01av04.pok.ibm.com (d01av04.pok.ibm.com [9.56.224.64]) by d01relay02.pok.ibm.com (8.13.8/8.13.8/NCO v9.1) with ESMTP id mBG021Ra172800 for ; Mon, 15 Dec 2008 19:02:01 -0500 Received: from d01av04.pok.ibm.com (loopback [127.0.0.1]) by d01av04.pok.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id mBG12BZO013134 for ; Mon, 15 Dec 2008 20:02:11 -0500 Content-Disposition: inline In-Reply-To: <20081215.153920.105386030.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, Dec 15, 2008 at 03:39:20PM -0800, David Miller wrote: > From: "Paul E. McKenney" > Date: Mon, 15 Dec 2008 15:29:42 -0800 > > > On Sat, Dec 13, 2008 at 12:35:21PM +1100, Herbert Xu wrote: > > > +static int napi_gro_complete(struct sk_buff *skb) > > > +{ > > > + struct packet_type *ptype; > > > + __be16 type = skb->protocol; > > > + struct list_head *head = &ptype_base[ntohs(type) & PTYPE_HASH_MASK]; > > > + int err = -ENOENT; > > > + > > > + if (!skb_shinfo(skb)->frag_list) > > > + goto out; > > > + > > > + rcu_read_lock(); > > > + list_for_each_entry_rcu(ptype, head, list) { > > > + if (ptype->type != type || ptype->dev || !ptype->gro_complete) > > > + continue; > > > + > > > + err = ptype->gro_complete(skb); > > > + break; > > > + } > > > + rcu_read_unlock(); > > > + > > > + if (err) { > > > + WARN_ON(&ptype->list == head); > > > > Presumably ptype_base[] is a static array rather than a dynamically > > allocated array that is resized under RCU protection, right? Otherwise, > > you could get in trouble if the above raced with the resize operation due > > to the fact that you are outside of the RCU read-side critical section. > > Yes, and we've been using RCU this way for this table for quite > some time. From net/core/dev.c: > > #define PTYPE_HASH_SIZE (16) > #define PTYPE_HASH_MASK (PTYPE_HASH_SIZE - 1) > > static DEFINE_SPINLOCK(ptype_lock); > static struct list_head ptype_base[PTYPE_HASH_SIZE] __read_mostly; > static struct list_head ptype_all __read_mostly; /* Taps */ Works for me, then! Thanx, Paul