Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756217Ab3JIWqO (ORCPT ); Wed, 9 Oct 2013 18:46:14 -0400 Received: from e36.co.us.ibm.com ([32.97.110.154]:39211 "EHLO e36.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753662Ab3JIWqM (ORCPT ); Wed, 9 Oct 2013 18:46:12 -0400 Date: Wed, 9 Oct 2013 15:46:04 -0700 From: "Paul E. McKenney" To: Josh Triplett Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, darren@dvhart.com, fweisbec@gmail.com, sbw@mit.edu, "David S. Miller" , Thomas Graf , Gao feng , Stephen Hemminger , linux-decnet-user@lists.sourceforge.net, netdev@vger.kernel.org Subject: Re: [PATCH v2 tip/core/rcu 05/13] decnet: Apply rcu_access_pointer() to avoid sparse false positive Message-ID: <20131009224604.GF5790@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20131009212920.GA15413@linux.vnet.ibm.com> <1381354186-16285-1-git-send-email-paulmck@linux.vnet.ibm.com> <1381354186-16285-5-git-send-email-paulmck@linux.vnet.ibm.com> <20131009222842.GD11709@jtriplet-mobl1> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131009222842.GD11709@jtriplet-mobl1> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13100922-3532-0000-0000-0000020CA6C2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2710 Lines: 71 On Wed, Oct 09, 2013 at 03:28:42PM -0700, Josh Triplett wrote: > On Wed, Oct 09, 2013 at 02:29:38PM -0700, Paul E. McKenney wrote: > > From: "Paul E. McKenney" > > > > The sparse checking for rcu_assign_pointer() was recently upgraded > > to reject non-__kernel address spaces. This also rejects __rcu, > > which is almost always the right thing to do. However, the use in > > dn_insert_route() is legitimate: It is assigning a pointer to an element > > Nit: "uses ... are", not "use ... is". :) Don't I already have "use ... is"? Thanx, Paul > > from an RCU-protected list, and all elements of this list are already > > visible to caller. > > > > This commit therefore silences this false positive by laundering the > > pointer using rcu_access_pointer() as suggested by Josh Triplett. > > > > Reported-by: kbuild test robot > > Signed-off-by: Paul E. McKenney > > Cc: "David S. Miller" > > Cc: Thomas Graf > > Cc: Gao feng > > Cc: Stephen Hemminger > > Cc: linux-decnet-user@lists.sourceforge.net > > Cc: netdev@vger.kernel.org > > With or without the above typo fix: > > Reviewed-by: Josh Triplett > > > --- > > net/decnet/dn_route.c | 5 +++-- > > 1 file changed, 3 insertions(+), 2 deletions(-) > > > > diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c > > index fe32388ea24f..3b1357bcfc92 100644 > > --- a/net/decnet/dn_route.c > > +++ b/net/decnet/dn_route.c > > @@ -345,7 +345,7 @@ static int dn_insert_route(struct dn_route *rt, unsigned int hash, struct dn_rou > > /* Put it first */ > > *rthp = rth->dst.dn_next; > > rcu_assign_pointer(rth->dst.dn_next, > > - dn_rt_hash_table[hash].chain); > > + rcu_access_pointer(dn_rt_hash_table[hash].chain)); > > rcu_assign_pointer(dn_rt_hash_table[hash].chain, rth); > > > > dst_use(&rth->dst, now); > > @@ -358,7 +358,8 @@ static int dn_insert_route(struct dn_route *rt, unsigned int hash, struct dn_rou > > rthp = &rth->dst.dn_next; > > } > > > > - rcu_assign_pointer(rt->dst.dn_next, dn_rt_hash_table[hash].chain); > > + rcu_assign_pointer(rt->dst.dn_next, > > + rcu_access_pointer(dn_rt_hash_table[hash].chain)); > > rcu_assign_pointer(dn_rt_hash_table[hash].chain, rt); > > > > dst_use(&rt->dst, now); > > -- > > 1.8.1.5 > > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/