From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:content-type:content-transfer-encoding; bh=5nDhXmLWp0H3WOmGkV8mMCxNnySlWEss5tzQyZFVW2Q=; b=jXz9Q7s2lGtSUCQlMulZZ/fngKztwvooWnHdBp7x+W7kob4bOeWnrCnjhLpTrUI8h6 f5d1yq8tUUMKk5p5z0xuQcZyV7JJbIjBnZCfB4n3kY5hPSB53FCrcAKk0f5oQU8u6mKQ kyDHuSh8nWa2CWRUVB4CfHWDQV3IxcTxCa3EpmXlFuCUA3ZgC8HAQe3eSFuxpsSmlWWi g2p3oon44aRbFLy3H6vGm4w191CbkrGQBnuUwHp4jVFXKDUSKa6578TPi6fGYhKK7EXg r5bvC/x8LjhbNZzh3lWuhgKtLjKQ3BL9ylphXkTzOVzYJuH6oySQIcmvwjjfkzVVi6D0 U03Q== Message-ID: <5286F550.10900@gmail.com> From: Ding Tianhong MIME-Version: 1.0 References: <20131116003946.GA316@linux.vnet.ibm.com> <1384562417-817-1-git-send-email-paulmck@linux.vnet.ibm.com> <1384562417-817-11-git-send-email-paulmck@linux.vnet.ibm.com> In-Reply-To: <1384562417-817-11-git-send-email-paulmck@linux.vnet.ibm.com> Content-Type: text/plain; charset="gb2312" Content-Transfer-Encoding: base64 Subject: Re: [Bridge] [PATCH tip/core/rcu 11/14] bonding/bond_main: Apply ACCESS_ONCE() to avoid sparse false positive List-Id: Linux Ethernet Bridging List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Date: Sat, 16 Nov 2013 04:43:16 -0000 To: "Paul E. McKenney" Cc: Stephen Hemminger , tglx@linutronix.de, laijs@cn.fujitsu.com, edumazet@google.com, "David S. Miller" , peterz@infradead.org, fweisbec@gmail.com, bridge@lists.linux-foundation.org, linux-kernel@vger.kernel.org, rostedt@goodmis.org, josh@joshtriplett.org, dhowells@redhat.com, sbw@mit.edu, niv@us.ibm.com, netdev@vger.kernel.org, mathieu.desnoyers@efficios.com, dipankar@in.ibm.com, darren@dvhart.com, akpm@linux-foundation.org, mingo@kernel.org 09ogMjAxMy8xMS8xNiA4OjQwLCBQYXVsIEUuIE1jS2VubmV5INC0tcA6Cj4gRnJvbTogIlBhdWwg RS4gTWNLZW5uZXkiIDxwYXVsbWNrQGxpbnV4LnZuZXQuaWJtLmNvbT4KPgo+IFRoZSBzcGFyc2Ug Y2hlY2tpbmcgZm9yIHJjdV9hc3NpZ25fcG9pbnRlcigpIHdhcyByZWNlbnRseSB1cGdyYWRlZAo+ IHRvIHJlamVjdCBub24tX19rZXJuZWwgYWRkcmVzcyBzcGFjZXMuICBUaGlzIGFsc28gcmVqZWN0 cyBfX3JjdSwKPiB3aGljaCBpcyBhbG1vc3QgYWx3YXlzIHRoZSByaWdodCB0aGluZyB0byBkby4g IEhvd2V2ZXIsIHRoZSB1c2VzIGluCj4gYm9uZF9jaGFuZ2VfYWN0aXZlX3NsYXZlKCkgYW5kIF9f Ym9uZF9yZWxlYXNlX29uZSgpIGFyZSBsZWdpdGltYXRlOgo+IFRoZXkgYXJlIGFzc2lnbmluZyBh IHBvaW50ZXIgdG8gYW4gZWxlbWVudCBmcm9tIGFuIFJDVS1wcm90ZWN0ZWQgbGlzdAo+IChvciBh IE5VTEwgcG9pbnRlciksIGFuZCBhbGwgZWxlbWVudHMgb2YgdGhpcyBsaXN0IGFyZSBhbHJlYWR5 IHZpc2libGUKPiB0byBjYWxsZXIuCj4KPiBUaGlzIGNvbW1pdCB0aGVyZWZvcmUgc2lsZW5jZXMg dGhlc2UgZmFsc2UgcG9zaXRpdmVzIGVpdGhlciBieSBsYXVuZGVyaW5nCj4gdGhlIHBvaW50ZXJz IHVzaW5nIEFDQ0VTU19PTkNFKCkgYXMgc3VnZ2VzdGVkIGJ5IEVyaWMgRHVtYXpldCBhbmQgSm9z aAo+IFRyaXBsZXR0LCBvciBieSB1c2luZyBSQ1VfSU5JVF9QT0lOVEVSKCkgZm9yIE5VTEwgcG9p bnRlciBhc3NpZ25tZW50cy4KSSB0aGluayBpdCBpcyBmaXQgZm9yIG5ldC1uZXh0LgoKCj4gUmVw b3J0ZWQtYnk6IGtidWlsZCB0ZXN0IHJvYm90IDxmZW5nZ3Vhbmcud3VAaW50ZWwuY29tPgo+IFNp Z25lZC1vZmYtYnk6IFBhdWwgRS4gTWNLZW5uZXkgPHBhdWxtY2tAbGludXgudm5ldC5pYm0uY29t Pgo+IENjOiBTdGVwaGVuIEhlbW1pbmdlciA8c3RlcGhlbkBuZXR3b3JrcGx1bWJlci5vcmc+Cj4g Q2M6ICJEYXZpZCBTLiBNaWxsZXIiIDxkYXZlbUBkYXZlbWxvZnQubmV0Pgo+IENjOiBicmlkZ2VA bGlzdHMubGludXgtZm91bmRhdGlvbi5vcmcKPiBDYzogbmV0ZGV2QHZnZXIua2VybmVsLm9yZwo+ IC0tLQo+ICBkcml2ZXJzL25ldC9ib25kaW5nL2JvbmRfbWFpbi5jIHwgNSArKystLQo+ICAxIGZp bGUgY2hhbmdlZCwgMyBpbnNlcnRpb25zKCspLCAyIGRlbGV0aW9ucygtKQo+Cj4gZGlmZiAtLWdp dCBhL2RyaXZlcnMvbmV0L2JvbmRpbmcvYm9uZF9tYWluLmMgYi9kcml2ZXJzL25ldC9ib25kaW5n L2JvbmRfbWFpbi5jCj4gaW5kZXggNzJkZjM5OWM0YWIzLi5iYmQ3ZmQzZTQ2ZmUgMTAwNjQ0Cj4g LS0tIGEvZHJpdmVycy9uZXQvYm9uZGluZy9ib25kX21haW4uYwo+ICsrKyBiL2RyaXZlcnMvbmV0 L2JvbmRpbmcvYm9uZF9tYWluLmMKPiBAQCAtODkwLDcgKzg5MCw4IEBAIHZvaWQgYm9uZF9jaGFu Z2VfYWN0aXZlX3NsYXZlKHN0cnVjdCBib25kaW5nICpib25kLCBzdHJ1Y3Qgc2xhdmUgKm5ld19h Y3RpdmUpCj4gIAkJaWYgKG5ld19hY3RpdmUpCj4gIAkJCWJvbmRfc2V0X3NsYXZlX2FjdGl2ZV9m bGFncyhuZXdfYWN0aXZlKTsKPiAgCX0gZWxzZSB7Cj4gLQkJcmN1X2Fzc2lnbl9wb2ludGVyKGJv bmQtPmN1cnJfYWN0aXZlX3NsYXZlLCBuZXdfYWN0aXZlKTsKPiArCQkvKiBCb3RoIC0tcmN1IGFu ZCB2aXNpYmxlLCBzbyBBQ0NFU1NfT05DRSgpIGlzIE9LLiAqLwo+ICsJCUFDQ0VTU19PTkNFKGJv bmQtPmN1cnJfYWN0aXZlX3NsYXZlKSA9IG5ld19hY3RpdmU7Cj4gIAl9Cj4gIAo+ICAJaWYgKGJv bmQtPnBhcmFtcy5tb2RlID09IEJPTkRfTU9ERV9BQ1RJVkVCQUNLVVApIHsKPiBAQCAtMTgwMSw3 ICsxODAyLDcgQEAgc3RhdGljIGludCBfX2JvbmRfcmVsZWFzZV9vbmUoc3RydWN0IG5ldF9kZXZp Y2UgKmJvbmRfZGV2LAo+ICAJfQo+ICAKPiAgCWlmIChhbGwpIHsKPiAtCQlyY3VfYXNzaWduX3Bv aW50ZXIoYm9uZC0+Y3Vycl9hY3RpdmVfc2xhdmUsIE5VTEwpOwo+ICsJCVJDVV9JTklUX1BPSU5U RVIoYm9uZC0+Y3Vycl9hY3RpdmVfc2xhdmUsIE5VTEwpOwo+ICAJfSBlbHNlIGlmIChvbGRjdXJy ZW50ID09IHNsYXZlKSB7Cj4gIAkJLyoKPiAgCQkgKiBOb3RlIHRoYXQgd2UgaG9sZCBSVE5MIG92 ZXIgdGhpcyBzZXF1ZW5jZSwgc28gdGhlcmUKCg== From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753897Ab3KPEnW (ORCPT ); Fri, 15 Nov 2013 23:43:22 -0500 Received: from mail-pb0-f54.google.com ([209.85.160.54]:63956 "EHLO mail-pb0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752244Ab3KPEnQ (ORCPT ); Fri, 15 Nov 2013 23:43:16 -0500 Message-ID: <5286F550.10900@gmail.com> Date: Sat, 16 Nov 2013 12:32:16 +0800 From: Ding Tianhong User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:17.0) Gecko/20130801 Thunderbird/17.0.8 MIME-Version: 1.0 To: "Paul E. McKenney" 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, josh@joshtriplett.org, 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, Stephen Hemminger , "David S. Miller" , bridge@lists.linux-foundation.org, netdev@vger.kernel.org Subject: Re: [PATCH tip/core/rcu 11/14] bonding/bond_main: Apply ACCESS_ONCE() to avoid sparse false positive References: <20131116003946.GA316@linux.vnet.ibm.com> <1384562417-817-1-git-send-email-paulmck@linux.vnet.ibm.com> <1384562417-817-11-git-send-email-paulmck@linux.vnet.ibm.com> In-Reply-To: <1384562417-817-11-git-send-email-paulmck@linux.vnet.ibm.com> Content-Type: text/plain; charset=GB2312 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ÓÚ 2013/11/16 8:40, Paul E. McKenney дµÀ: > 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 uses in > bond_change_active_slave() and __bond_release_one() are legitimate: > They are assigning a pointer to an element from an RCU-protected list > (or a NULL pointer), and all elements of this list are already visible > to caller. > > This commit therefore silences these false positives either by laundering > the pointers using ACCESS_ONCE() as suggested by Eric Dumazet and Josh > Triplett, or by using RCU_INIT_POINTER() for NULL pointer assignments. I think it is fit for net-next. > Reported-by: kbuild test robot > Signed-off-by: Paul E. McKenney > Cc: Stephen Hemminger > Cc: "David S. Miller" > Cc: bridge@lists.linux-foundation.org > Cc: netdev@vger.kernel.org > --- > drivers/net/bonding/bond_main.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c > index 72df399c4ab3..bbd7fd3e46fe 100644 > --- a/drivers/net/bonding/bond_main.c > +++ b/drivers/net/bonding/bond_main.c > @@ -890,7 +890,8 @@ void bond_change_active_slave(struct bonding *bond, struct slave *new_active) > if (new_active) > bond_set_slave_active_flags(new_active); > } else { > - rcu_assign_pointer(bond->curr_active_slave, new_active); > + /* Both --rcu and visible, so ACCESS_ONCE() is OK. */ > + ACCESS_ONCE(bond->curr_active_slave) = new_active; > } > > if (bond->params.mode == BOND_MODE_ACTIVEBACKUP) { > @@ -1801,7 +1802,7 @@ static int __bond_release_one(struct net_device *bond_dev, > } > > if (all) { > - rcu_assign_pointer(bond->curr_active_slave, NULL); > + RCU_INIT_POINTER(bond->curr_active_slave, NULL); > } else if (oldcurrent == slave) { > /* > * Note that we hold RTNL over this sequence, so there