From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bart Van Assche Subject: Re: rtnl_lock deadlock on 3.10 Date: Thu, 05 Sep 2013 12:02:12 +0200 Message-ID: <522856A4.8040800@acm.org> References: <20130701145456.GA7756@sbohrermbp13-local.rgmadvisors.com> <20130702082818.GA26178@order.stressinduktion.org> <20130703051152.GA12615@order.stressinduktion.org> <20130703053307.GB12615@order.stressinduktion.org> <20130703172239.GA3439@sbohrermbp13-local.rgmadvisors.com> <51D45EB3.7030404@mellanox.com> <20130715143819.GA3084@sbohrermbp13-local.rgmadvisors.com> <20130729230216.GB4396@sbohrermbp13-local.rgmadvisors.com> <51F7B792.7030803@opengridcomputing.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Shawn Bohrer , Or Gerlitz , Shawn Bohrer , Cong Wang , netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, roland-BHEL68pLQRGGvPXPguhicg@public.gmane.org, swise-ut6Up61K2wZBDgjK7y7TUQ@public.gmane.org To: Steve Wise Return-path: In-Reply-To: <51F7B792.7030803-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: netdev.vger.kernel.org On 07/30/13 14:54, Steve Wise wrote: > On 7/29/2013 6:02 PM, Shawn Bohrer wrote: >> On Mon, Jul 15, 2013 at 09:38:19AM -0500, Shawn Bohrer wrote: >>> On Wed, Jul 03, 2013 at 08:26:11PM +0300, Or Gerlitz wrote: >>>> On 03/07/2013 20:22, Shawn Bohrer wrote: >>>>> On Wed, Jul 03, 2013 at 07:33:07AM +0200, Hannes Frederic Sowa wrote: >>>>>> On Wed, Jul 03, 2013 at 07:11:52AM +0200, Hannes Frederic Sowa wrote: >>>>>>> On Tue, Jul 02, 2013 at 01:38:26PM +0000, Cong Wang wrote: >>>>>>>> On Tue, 02 Jul 2013 at 08:28 GMT, Hannes Frederic Sowa >>>>>>>> wrote: >>>>>>>>> On Mon, Jul 01, 2013 at 09:54:56AM -0500, Shawn Bohrer wrote: >>>>>>>>>> I've managed to hit a deadlock at boot a couple times while >>>>>>>>>> testing >>>>>>>>>> the 3.10 rc kernels. It seems to always happen when my network >>>>>>>>>> devices are initializing. This morning I updated to v3.10 and >>>>>>>>>> made a >>>>>>>>>> few config tweaks and so far I've hit it 4 out of 5 reboots. >>>>>>>>>> It looks >>>>>>>>>> like most processes are getting stuck on rtnl_lock. Below is >>>>>>>>>> a boot >>>>>>>>>> log with the soft lockup prints. Please let know if there is any >>>>>>>>>> other information I can provide: >>>>>>>>> Could you try a build with CONFIG_LOCKDEP enabled? >>>>>>>>> >>>>>>>> The problem is clear: ib_register_device() is called with >>>>>>>> rtnl_lock, >>>>>>>> but itself needs device_mutex, however, ib_register_client() first >>>>>>>> acquires device_mutex, then indirectly calls register_netdev() >>>>>>>> which >>>>>>>> takes rtnl_lock. Deadlock! >>>>>>>> >>>>>>>> One possible fix is always taking rtnl_lock before taking >>>>>>>> device_mutex, something like below: >>>>>>>> >>>>>>>> diff --git a/drivers/infiniband/core/device.c >>>>>>>> b/drivers/infiniband/core/device.c >>>>>>>> index 18c1ece..890870b 100644 >>>>>>>> --- a/drivers/infiniband/core/device.c >>>>>>>> +++ b/drivers/infiniband/core/device.c >>>>>>>> @@ -381,6 +381,7 @@ int ib_register_client(struct ib_client >>>>>>>> *client) >>>>>>>> { >>>>>>>> struct ib_device *device; >>>>>>>> + rtnl_lock(); >>>>>>>> mutex_lock(&device_mutex); >>>>>>>> list_add_tail(&client->list, &client_list); >>>>>>>> @@ -389,6 +390,7 @@ int ib_register_client(struct ib_client >>>>>>>> *client) >>>>>>>> client->add(device); >>>>>>>> mutex_unlock(&device_mutex); >>>>>>>> + rtnl_unlock(); >>>>>>>> return 0; >>>>>>>> } >>>>>>>> diff --git a/drivers/infiniband/ulp/ipoib/ipoib_main.c >>>>>>>> b/drivers/infiniband/ulp/ipoib/ipoib_main.c >>>>>>>> index b6e049a..5a7a048 100644 >>>>>>>> --- a/drivers/infiniband/ulp/ipoib/ipoib_main.c >>>>>>>> +++ b/drivers/infiniband/ulp/ipoib/ipoib_main.c >>>>>>>> @@ -1609,7 +1609,7 @@ static struct net_device >>>>>>>> *ipoib_add_port(const char *format, >>>>>>>> goto event_failed; >>>>>>>> } >>>>>>>> - result = register_netdev(priv->dev); >>>>>>>> + result = register_netdevice(priv->dev); >>>>>>>> if (result) { >>>>>>>> printk(KERN_WARNING "%s: couldn't register ipoib port >>>>>>>> %d; error %d\n", >>>>>>>> hca->name, port, result); >>>>>>> Looks good to me. Shawn, could you test this patch? >>>>>> ib_unregister_device/ib_unregister_client would need the same change, >>>>>> too. I have not checked the other ->add() and ->remove() >>>>>> functions. Also >>>>>> cc'ed linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Roland Dreier. >>>>> Cong's patch is missing the #include but otherwise >>>>> I've had 34 successful reboots with no deadlocks which is a good sign. >>>>> It sounds like there are more paths that need to be audited and a >>>>> proper patch submitted. I can do more testing later if needed. >>>>> >>>>> Thanks, >>>>> Shawn >>>>> >>>> Guys, I was a bit busy today looking into that, but I don't think we >>>> want the IB core layer (core/device.c) to >>>> use rtnl locking which is something that belongs to the network stack. >>> Has anymore thought been put into a proper fix for this issue? >> I'm no expert in this area but I'm having a hard time seeing a >> different solution than the one Cong suggested. Just to be clear the >> deadlock I hit was between cxgb3 and the ipoib module, so I've Cc'd >> Steve Wise in case he has a better solution from the Chelsio side. > > I don't know of another way to resolve this. The rtnl lock is used in > ipoib and mlx4 already. I think we should go forward with the proposed > patch. (replying to an e-mail of one month ago) Hello, It would be appreciated if anyone could report what the current status of this issue is. I think a deadlock I ran into with kernels 3.10 and 3.11 and PCI pass-through is related to this issue. See also http://bugzilla.kernel.org/show_bug.cgi?id=60856 for the lockdep report. Thanks, Bart. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html