From mboxrd@z Thu Jan 1 00:00:00 1970 From: Or Gerlitz Subject: Re: rtnl_lock deadlock on 3.10 Date: Wed, 3 Jul 2013 20:26:11 +0300 Message-ID: <51D45EB3.7030404@mellanox.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20130703172239.GA3439-/vebjAlq/uFE7V8Yqttd03bhEEblAqRIDbRjUBewulXQT0dZR+AlfA@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Shawn Bohrer Cc: Cong Wang , netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, roland-BHEL68pLQRGGvPXPguhicg@public.gmane.org, sbohrer-EgGFQ3RFNTIP7C3xziwOQw@public.gmane.org List-Id: linux-rdma@vger.kernel.org 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. Or. -- 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