From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753178AbaCXLMM (ORCPT ); Mon, 24 Mar 2014 07:12:12 -0400 Received: from charlotte.tuxdriver.com ([70.61.120.58]:39555 "EHLO smtp.tuxdriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750984AbaCXLMK (ORCPT ); Mon, 24 Mar 2014 07:12:10 -0400 Date: Mon, 24 Mar 2014 07:11:44 -0400 From: Neil Horman To: Monam Agarwal Cc: davem@davemloft.net, ebiederm@xmission.com, cwang@twopensource.com, kaber@trash.net, antonio@meshcoding.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] net/core: Use RCU_INIT_POINTER(x, NULL) in netpoll.c Message-ID: <20140324111144.GA19368@hmsreliant.think-freely.org> References: <1395601966-12490-1-git-send-email-monamagarwal123@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1395601966-12490-1-git-send-email-monamagarwal123@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Spam-Score: -2.9 (--) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 24, 2014 at 12:42:46AM +0530, Monam Agarwal wrote: > This patch replaces rcu_assign_pointer(x, NULL) with RCU_INIT_POINTER(x, NULL) > > The rcu_assign_pointer() ensures that the initialization of a structure > is carried out before storing a pointer to that structure. > And in the case of the NULL pointer, there is no structure to initialize. > So, rcu_assign_pointer(p, NULL) can be safely converted to RCU_INIT_POINTER(p, NULL) > > Signed-off-by: Monam Agarwal No, I don't think this is right. __netpoll_cleanup can be called in parallel with bottom half access to dev->npinfo. rcu_assign pointer is safe against those accesses, but RCU_INIT_POINTER is not. Neil > --- > net/core/netpoll.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/net/core/netpoll.c b/net/core/netpoll.c > index 7291dde..41c4e9c 100644 > --- a/net/core/netpoll.c > +++ b/net/core/netpoll.c > @@ -809,7 +809,7 @@ void __netpoll_cleanup(struct netpoll *np) > if (ops->ndo_netpoll_cleanup) > ops->ndo_netpoll_cleanup(np->dev); > > - rcu_assign_pointer(np->dev->npinfo, NULL); > + RCU_INIT_POINTER(np->dev->npinfo, NULL); > call_rcu_bh(&npinfo->rcu, rcu_cleanup_netpoll_info); > } > } > -- > 1.7.9.5 > >