Subject: [BUG] Probably lockdep bug Re: circular locking, mirred, 2.6.24.2

From: Jarek Poplawski <[email-masked]>
Date: Wed, 5 Mar 2008 13:54:48 +0000

Hi,

dev->queue_lock is taken in a scenario like below: always after
dev->ingress_lock and p->tcfc_lock, so just like on this last
backtrace with info about held locks. But this report shows that
lockdep for some reason forgot the history before dev->queue_lock,
and recorded it again. It seems, even if there is something wrong
with init lockdep shouldn't report it like this.

I CC this report to lockdep maintainers and linux-kernel.

Regards,
Jarek P.

Original lockdep report for 2.6.24.2:
http://permalink.gmane.org/gmane.linux.network/86896 

On Wed, Mar 05, 2008 at 12:45:51PM +0200, Denys Fedoryshchenko wrote:
> I did test on vanilla 2.6.25-rc3, on clean Gentoo distro and got 
> similar message. The strange thing, message appeared not immediately after 
> launching script, but after few seconds.
> 
> Scripts is the same. I have same message on another script, used for ppp 
> shaper.
> 
> [   10.536424] =======================================================
> [   10.536424] [ INFO: possible circular locking dependency detected ]
> [   10.536424] 2.6.25-rc3-devel #3
> [   10.536424] -------------------------------------------------------
> [   10.536424] swapper/0 is trying to acquire lock:
> [   10.536424]  (&dev->queue_lock){-+..}, at: [<c0299b4a>] 
> dev_queue_xmit+0x175/0x2f3
> [   10.536424]
> [   10.536424] but task is already holding lock:
> [   10.536424]  (&p->tcfc_lock){-+..}, at: [<f8a67154>] tcf_mirred+0x20/0x178 
> [act_mirred]
> [   10.536424]
> [   10.536424] which lock already depends on the new lock.
> [   10.536424]
> [   10.536424]
> [   10.536424] the existing dependency chain (in reverse order) is:
> [   10.536424]
> [   10.536424] -> #2 (&p->tcfc_lock){-+..}:
> [   10.536424]        [<c013efb6>] __lock_acquire+0x963/0xb18
> [   10.536424]        [<f8a67154>] tcf_mirred+0x20/0x178 [act_mirred]
> [   10.536424]        [<c013f1d7>] lock_acquire+0x6c/0x89
> [   10.536424]        [<f8a67154>] tcf_mirred+0x20/0x178 [act_mirred]
> [   10.536424]        [<c02f6927>] _spin_lock+0x1c/0x49
> [   10.536424]        [<f8a67154>] tcf_mirred+0x20/0x178 [act_mirred]
> [   10.536424]        [<f8a67134>] tcf_mirred+0x0/0x178 [act_mirred]
> [   10.536424]        [<f8a67154>] tcf_mirred+0x20/0x178 [act_mirred]
> [   10.536424]        [<c010b2ce>] save_stack_address+0x0/0x28
> [   10.536424]        [<f8a67134>] tcf_mirred+0x0/0x178 [act_mirred]
> [   10.536424]        [<c02a7018>] tcf_action_exec+0x44/0x77
> [   10.536424]        [<f89927b0>] u32_classify+0x119/0x24e [cls_u32]
> [   10.536424]        [<c013f123>] __lock_acquire+0xad0/0xb18
> [   10.536424]        [<c02a5006>] tc_classify_compat+0x2f/0x5e
> [   10.536424]        [<c02a5d1c>] tc_classify+0x17/0x78
> [   10.536424]        [<f89670a4>] ingress_enqueue+0x1a/0x53 [sch_ingress]
> [   10.536424]        [<c0297009>] netif_receive_skb+0x263/0x3e6
> [   10.536424]        [<f882b4d9>] e1000_clean_rx_irq+0x380/0x448 [e1000]
> [   10.536424]        [<f8828e1e>] e1000_clean+0x62/0x1fd [e1000]
> [   10.536424]        [<c029926f>] net_rx_action+0xb3/0x19e
> [   10.536424]        [<c01276f7>] __do_softirq+0x6f/0xe9
> [   10.536424]        [<c0106aa7>] do_softirq+0x5e/0xa8
> [   10.536424]        [<ffffffff>] 0xffffffff
> [   10.536424]
> [   10.536424] -> #1 (&dev->ingress_lock){-+..}:
> [   10.536424]        [<c013efb6>] __lock_acquire+0x963/0xb18
> [   10.536424]        [<c02a4718>] qdisc_lock_tree+0x1e/0x21
> [   10.536424]        [<c013f1d7>] lock_acquire+0x6c/0x89
> [   10.536424]        [<c02a4718>] qdisc_lock_tree+0x1e/0x21
> [   10.536424]        [<c02f6927>] _spin_lock+0x1c/0x49
> [   10.536424]        [<c02a4718>] qdisc_lock_tree+0x1e/0x21
> [   10.536424]        [<c02a4718>] qdisc_lock_tree+0x1e/0x21
> [   10.536424]        [<c02a4747>] dev_init_scheduler+0xb/0x4d
> [   10.536424]        [<c0298299>] register_netdevice+0x288/0x2e2
> [   10.536424]        [<c0298325>] register_netdev+0x32/0x3f
> [   10.536424]        [<c042a867>] loopback_net_init+0x34/0x63
> [   10.536424]        [<c0295b3f>] register_pernet_operations+0x13/0x15
> [   10.536424]        [<c0295ba8>] register_pernet_device+0x1f/0x4c
> [   10.536424]        [<c042a831>] loopback_init+0xd/0xf
> [   10.536424]        [<c0415478>] kernel_init+0x132/0x27c
> [   10.536424]        [<c0415346>] kernel_init+0x0/0x27c
> [   10.536424]        [<c0415346>] kernel_init+0x0/0x27c
> [   10.536424]        [<c01056bf>] kernel_thread_helper+0x7/0x10
> [   10.536424]        [<ffffffff>] 0xffffffff
> [   10.536424]
> [   10.536424] -> #0 (&dev->queue_lock){-+..}:
> [   10.536424]        [<c013d169>] print_circular_bug_tail+0x2e/0x66
> [   10.536424]        [<c013eedd>] __lock_acquire+0x88a/0xb18
> [   10.536424]        [<c013f1d7>] lock_acquire+0x6c/0x89
> [   10.536424]        [<c0299b4a>] dev_queue_xmit+0x175/0x2f3
> [   10.536424]        [<c02f6927>] _spin_lock+0x1c/0x49
> [   10.536424]        [<c0299b4a>] dev_queue_xmit+0x175/0x2f3
> [   10.536425]        [<c0299b4a>] dev_queue_xmit+0x175/0x2f3
> [   10.536425]        [<f8a6728b>] tcf_mirred+0x157/0x178 [act_mirred]
> [   10.536425]        [<f8a67134>] tcf_mirred+0x0/0x178 [act_mirred]
> [   10.536425]        [<c02a7018>] tcf_action_exec+0x44/0x77
> [   10.536425]        [<f89927b0>] u32_classify+0x119/0x24e [cls_u32]
> [   10.536425]        [<c013f123>] __lock_acquire+0xad0/0xb18
> [   10.536425]        [<c02a5006>] tc_classify_compat+0x2f/0x5e
> [   10.536425]        [<c02a5d1c>] tc_classify+0x17/0x78
> [   10.536425]        [<f89670a4>] ingress_enqueue+0x1a/0x53 [sch_ingress]
> [   10.536425]        [<c0297009>] netif_receive_skb+0x263/0x3e6
> [   10.536425]        [<f882b4d9>] e1000_clean_rx_irq+0x380/0x448 [e1000]
> [   10.536425]        [<f8828e1e>] e1000_clean+0x62/0x1fd [e1000]
> [   10.536425]        [<c029926f>] net_rx_action+0xb3/0x19e
> [   10.536425]        [<c01276f7>] __do_softirq+0x6f/0xe9
> [   10.536425]        [<c0106aa7>] do_softirq+0x5e/0xa8
> [   10.536425]        [<ffffffff>] 0xffffffff
> [   10.536425]
> [   10.536425] other info that might help us debug this:
> [   10.536425]
> [   10.536425] 5 locks held by swapper/0:
> [   10.536425]  #0:  (rcu_read_lock){..--}, at: [<c029920c>] 
> net_rx_action+0x50/0x19e
> [   10.536425]  #1:  (rcu_read_lock){..--}, at: [<c0296e96>] 
> netif_receive_skb+0xf0/0x3e6
> [   10.536425]  #2:  (&dev->ingress_lock){-+..}, at: [<c0296ff5>] 
> netif_receive_skb+0x24f/0x3e6
> [   10.536425]  #3:  (&p->tcfc_lock){-+..}, at: [<f8a67154>] tcf_mirred+0x20/
> 0x178 [act_mirred]
> [   10.536425]  #4:  (rcu_read_lock){..--}, at: [<c0299afb>] 
> dev_queue_xmit+0x126/0x2f3
> [   10.536425]
> [   10.536425] stack backtrace:
> [   10.536425] Pid: 0, comm: swapper Not tainted 2.6.25-rc3-devel #3
> [   10.536425]  [<c013d196>] print_circular_bug_tail+0x5b/0x66
> [   10.536425]  [<c013eedd>] __lock_acquire+0x88a/0xb18
> [   10.536425]  [<c013f1d7>] lock_acquire+0x6c/0x89
> [   10.536425]  [<c0299b4a>] ? dev_queue_xmit+0x175/0x2f3
> [   10.536425]  [<c02f6927>] _spin_lock+0x1c/0x49
> [   10.536425]  [<c0299b4a>] ? dev_queue_xmit+0x175/0x2f3
> [   10.536425]  [<c0299b4a>] dev_queue_xmit+0x175/0x2f3
> [   10.536425]  [<f8a6728b>] tcf_mirred+0x157/0x178 [act_mirred]
> [   10.536425]  [<f8a67134>] ? tcf_mirred+0x0/0x178 [act_mirred]
> [   10.536425]  [<c02a7018>] tcf_action_exec+0x44/0x77
> [   10.536425]  [<f89927b0>] u32_classify+0x119/0x24e [cls_u32]
> [   10.536425]  [<c013f123>] ? __lock_acquire+0xad0/0xb18
> [   10.536425]  [<c02a5006>] tc_classify_compat+0x2f/0x5e
> [   10.536425]  [<c02a5d1c>] tc_classify+0x17/0x78
> [   10.536425]  [<f89670a4>] ingress_enqueue+0x1a/0x53 [sch_ingress]
> [   10.536425]  [<c0297009>] netif_receive_skb+0x263/0x3e6
> [   10.536425]  [<f882b4d9>] e1000_clean_rx_irq+0x380/0x448 [e1000]
> [   10.536425]  [<f8828e1e>] e1000_clean+0x62/0x1fd [e1000]
> [   10.536425]  [<c029926f>] net_rx_action+0xb3/0x19e
> [   10.536425]  [<c01276f7>] __do_softirq+0x6f/0xe9
> [   10.536425]  [<c0106aa7>] do_softirq+0x5e/0xa8
> [   10.536425]  [<c014d8c9>] ? handle_edge_irq+0x0/0x10a
> [   10.536425]  [<c0127655>] irq_exit+0x44/0x77
> [   10.536425]  [<c0106b91>] do_IRQ+0xa0/0xb7
> [   10.536425]  [<c0105446>] common_interrupt+0x2e/0x34
> [   10.536425]  [<c01031b9>] ? mwait_idle_with_hints+0x39/0x3d
> [   10.536425]  [<c0103364>] ? mwait_idle+0x0/0x14
> [   10.536425]  [<c0103376>] mwait_idle+0x12/0x14
> [   10.536425]  [<c0103696>] cpu_idle+0xb5/0xd5
> [   10.536425]  [<c02e5b79>] rest_init+0x49/0x4b
> 
> 
> 
> 
> On Mon, 25 Feb 2008 11:39:30 +0000, Jarek Poplawski wrote
> > On Mon, Feb 25, 2008 at 12:48:38PM +0200, Denys Fedoryshchenko wrote:
> > > What does it mean early?
> > > I have custom boot scripts, it is also custom system based on busybox. 
> There 
> > > is a chance that i forgot to bring ifb0 up, but thats it.
> > > I think such warning must not appear on any actions in userspace.
> > 
> > It's not about ifb0: this report shows loopback_init after some 
> > action on eth, so eth was probably up before lo. And of course you 
> > are right: this warning shouldn't be there. But, since this report 
> > looks very strange, I wonder if there could be something else that mislead
> > lockdep. Could you try to reproduce this with 2.6.24.2 without these
> > additional patches?
> > 
> > Jarek P.
> > --
> > To unsubscribe from this list: send the line "unsubscribe netdev" in
> > the body of a message to [email-masked]
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 
> 
> --
> Denys Fedoryshchenko
> Technical Manager
> Virtual ISP S.A.L.
>