From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jiri Pirko Subject: Re: [patch net-next v5 3/8] switchdev: allow caller to explicitly request attr_set as deferred Date: Fri, 16 Oct 2015 10:23:48 +0200 Message-ID: <20151016082347.GC2194@nanopsycho.orion> References: <1444844455-12508-1-git-send-email-jiri@resnulli.us> <1444844455-12508-4-git-send-email-jiri@resnulli.us> <561FC472.5030506@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, davem@davemloft.net, idosch@mellanox.com, eladr@mellanox.com, sfeldma@gmail.com, f.fainelli@gmail.com, linux@roeck-us.net, vivien.didelot@savoirfairelinux.com, andrew@lunn.ch, David.Laight@ACULAB.COM, stephen@networkplumber.org To: John Fastabend Return-path: Received: from mail-lf0-f54.google.com ([209.85.215.54]:35502 "EHLO mail-lf0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752122AbbJPIXv (ORCPT ); Fri, 16 Oct 2015 04:23:51 -0400 Received: by lffy185 with SMTP id y185so75114352lff.2 for ; Fri, 16 Oct 2015 01:23:50 -0700 (PDT) Content-Disposition: inline In-Reply-To: <561FC472.5030506@gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: Thu, Oct 15, 2015 at 05:21:22PM CEST, john.fastabend@gmail.com wrote: >On 15-10-14 10:40 AM, Jiri Pirko wrote: >> From: Jiri Pirko >> >> Caller should know if he can call attr_set directly (when holding RTNL) >> or if he has to defer the att_set processing for later. >> >> This also allows drivers to sleep inside attr_set and report operation >> status back to switchdev core. Switchdev core then warns if status is >> not ok, instead of silent errors happening in drivers. >> >> Benefit from newly introduced switchdev deferred ops infrastructure. >> > >A nit but the patch description should note your setting the defer bit >on the bridge set state. > >> Signed-off-by: Jiri Pirko >> --- >> include/net/switchdev.h | 1 + >> net/bridge/br_stp.c | 3 +- >> net/switchdev/switchdev.c | 108 ++++++++++++++++++---------------------------- >> 3 files changed, 46 insertions(+), 66 deletions(-) >> >> diff --git a/include/net/switchdev.h b/include/net/switchdev.h >> index d1c7f90..f7de6f8 100644 >> --- a/include/net/switchdev.h >> +++ b/include/net/switchdev.h >> @@ -17,6 +17,7 @@ >> >> #define SWITCHDEV_F_NO_RECURSE BIT(0) >> #define SWITCHDEV_F_SKIP_EOPNOTSUPP BIT(1) >> +#define SWITCHDEV_F_DEFER BIT(2) >> >> struct switchdev_trans_item { >> struct list_head list; >> diff --git a/net/bridge/br_stp.c b/net/bridge/br_stp.c >> index db6d243de..80c34d7 100644 >> --- a/net/bridge/br_stp.c >> +++ b/net/bridge/br_stp.c >> @@ -41,13 +41,14 @@ void br_set_state(struct net_bridge_port *p, unsigned int state) >> { >> struct switchdev_attr attr = { >> .id = SWITCHDEV_ATTR_ID_PORT_STP_STATE, >> + .flags = SWITCHDEV_F_DEFER, >> .u.stp_state = state, >> }; > > >This creates a possible race (with 6/8) I think, please check! Wait. This patch does not change the previous behaviour. Patch 6 does, so I don't understand why you are asking here. Confusing. > >In del_nbp() we call br_stp_disable_port() to set the port state >to BR_STATE_DISABLE and disabling learning events. But with this >patch it can be deferred. Also note the STP agent may be in userspace >which actually seems more likely the case because you likely want to >run some more modern variant of STP than the kernel supports. > >So at some point in the future the driver will turn off learning. At >the same time we call br_fdb_delete_by_port which calls a deferred >set of fdb deletes. > >I don't see how you guarantee learning is off before you start doing >the deletes here and possibly learning new addresses after the software >side believes the port is down. > >So > > br_stp_disable_port > br_fdb_delete_by_port > {fdb_del_external_learn} > [hw learns a fdb] > [hw disables learning] > >What stops this from happening? Okay. This behaviour is the same as without the patchset. What would resolve the issue it to put switchdev_deferred_process() after br_stp_disable_port() and before br_fdb_delete_by_port() call. That would enforce stp change to happen in hw before fdbs are explicitly deleted. Sound good to you? >