From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH net] virtio-net: add a missing synchronize_net() Date: Wed, 16 Nov 2016 15:55:46 +0200 Message-ID: <20161116155537-mutt-send-email-mst@kernel.org> References: <1479277452.8455.156.camel@edumazet-glaptop3.roam.corp.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: David Miller , netdev , Jason Wang To: Eric Dumazet Return-path: Received: from mx1.redhat.com ([209.132.183.28]:58948 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753215AbcKPNzs (ORCPT ); Wed, 16 Nov 2016 08:55:48 -0500 Content-Disposition: inline In-Reply-To: <1479277452.8455.156.camel@edumazet-glaptop3.roam.corp.google.com> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, Nov 15, 2016 at 10:24:12PM -0800, Eric Dumazet wrote: > From: Eric Dumazet > > It seems many drivers do not respect napi_hash_del() contract. > > When napi_hash_del() is used before netif_napi_del(), an RCU grace > period is needed before freeing NAPI object. > > Fixes: 91815639d880 ("virtio-net: rx busy polling support") > Signed-off-by: Eric Dumazet > Cc: Jason Wang > Cc: Michael S. Tsirkin Acked-by: Michael S. Tsirkin > --- > drivers/net/virtio_net.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index fd8b1e62301f..7276d5a95bd0 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -1497,6 +1497,11 @@ static void virtnet_free_queues(struct virtnet_info *vi) > netif_napi_del(&vi->rq[i].napi); > } > > + /* We called napi_hash_del() before netif_napi_del(), > + * we need to respect an RCU grace period before freeing vi->rq > + */ > + synchronize_net(); > + > kfree(vi->rq); > kfree(vi->sq); > } >