From mboxrd@z Thu Jan 1 00:00:00 1970 From: dingtianhong Subject: Re: [PATCH] bonding: add synchronize_net() after netdev_rx_handler_unregister Date: Thu, 23 May 2013 09:41:30 +0800 Message-ID: <519D73CA.8090200@huawei.com> References: <519C8504.1080906@huawei.com> <1369223145.3301.308.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Jay Vosburgh , Andy Gospodarek , "David S. Miller" , Eric Dumazet , Netdev , Li Zefan To: Eric Dumazet Return-path: Received: from szxga01-in.huawei.com ([119.145.14.64]:33152 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756946Ab3EWBmJ (ORCPT ); Wed, 22 May 2013 21:42:09 -0400 In-Reply-To: <1369223145.3301.308.camel@edumazet-glaptop> Sender: netdev-owner@vger.kernel.org List-ID: On 2013/5/22 19:45, Eric Dumazet wrote: > On Wed, 2013-05-22 at 16:42 +0800, dingtianhong wrote: >> commit 00cfec3748 (net: add a synchronize_net() ...) add a synchronize_net() >> in netdev_rx_handler_unregister() to guarantee the rx_handler is NULL when >> rx_handler_data is a non NULL in rcu_read_lock(). >> >> so the caller should not use netdev_rx_handler_unregister in atomic as it may >> schedule and sleep, the commit fcd99434f fix the bug in bond release, but the >> problem is no action to guarantee the rx_handler_data is NULL when bond release, >> so add synchronize_net() and fix it. >> >> This patch adds more comments to netdev_rx_handler_unregister(). >> >> Signed-off-by: Ding Tianhong >> --- >> drivers/net/bonding/bond_main.c | 2 ++ >> net/core/dev.c | 3 +++ >> 2 files changed, 5 insertions(+) >> >> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c >> index d0aade0..592a603 100644 >> --- a/drivers/net/bonding/bond_main.c >> +++ b/drivers/net/bonding/bond_main.c >> @@ -2007,6 +2007,8 @@ static int __bond_release_one(struct net_device *bond_dev, >> * for this slave anymore. >> */ >> netdev_rx_handler_unregister(slave_dev); >> + synchronize_net(); >> + >> write_lock_bh(&bond->lock); >> > > Patch is not needed. > > This was discussed on netdev, please read the archives. > > Its even documented in netdev_rx_handler_unregister(), could you please > read again commit [1] > > What about you describe the problems you really noticed ? > > [1] commit > 00cfec37484761a44a3b6f4675a54caa618210ae > ("net: add a synchronize_net() in netdev_rx_handler_unregister()") > > I totally understand the commit [1] and know the problem that you met at that time, but its not a net core problem, its drivers problem, the function synchronize_net() need to follow netdev_rx_handler_unregister() even though netdev_rx_handler_unregister() has its own synchronize_net(), the commit [2] fcd99434f fix drivers problem follow your opinion, but miss synchronize_net(),so add it. > > . >