linux-kernel - Re: BUG: spinlock bad magic on CPU#1, swapper/1

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Message-ID: <20090805100329.GB3897@psychotron.englab.brq.redhat.com>
Date:	Wed, 5 Aug 2009 12:03:29 +0200
From:	Jiri Pirko <jpirko@...hat.com>
To:	Frans Pop <elendil@...net.nl>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	netdev@...r.kernel.org
Subject: Re: BUG: spinlock bad magic on CPU#1, swapper/1

Wed, Aug 05, 2009 at 11:50:52AM CEST, elendil@...net.nl wrote:
>On Wednesday 05 August 2009, Frans Pop wrote:
>> Current v2.6.31-rc5-246-g90bc1a6 gives me:
>>
>> BUG: spinlock bad magic on CPU#1, swapper/1
>>  lock: ffff88007e1889c8, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0
>> Pid: 1, comm: swapper Not tainted 2.6.31-rc5 #4 
>> Call Trace:
>>  [<ffffffff811345e8>] spin_bug+0xa2/0xaa
>>  [<ffffffff8113469e>] _raw_spin_lock+0x23/0x135
>>  [<ffffffff8125664e>] _spin_lock_bh+0x19/0x1e
>>  [<ffffffff811e3702>] alloc_netdev_mq+0x127/0x211
>>  [<ffffffff81433487>] ? netdev_init+0x6a/0xac
>>  [<ffffffff811a81eb>] ? loopback_setup+0x0/0x7b
>>  [<ffffffff8142e718>] loopback_net_init+0x30/0x7a
>>  [<ffffffff811dd62e>] register_pernet_device+0x2b/0x58
>>  [<ffffffff814336bd>] net_dev_init+0x13d/0x19b
>>  [<ffffffff81433580>] ? net_dev_init+0x0/0x19b
>>  [<ffffffff8100905c>] do_one_initcall+0x56/0x12b
>>  [<ffffffff8106f55b>] ? register_irq_proc+0xb0/0xcc
>>  [<ffffffff810e0000>] ? proc_pid_cmdline+0x5a/0xf9
>>  [<ffffffff8140f65d>] kernel_init+0x14d/0x1a3
>>  [<ffffffff8100ca7a>] child_rip+0xa/0x20
>>  [<ffffffff8140f510>] ? kernel_init+0x0/0x1a3
>>  [<ffffffff8100ca70>] ? child_rip+0x0/0x20
>>
>> Error occurs during early boot (between PCI/ACPI init and PnP init).
>
>Reverting the following commit fixes it:

Sure it fixes it but it also exposes the previous bug. I would rather suggest
to go with Ingo's patch.

Jirka

>commit a6ac65db2329e7685299666f5f7b6093c7b0f3a0
>Author: Jiri Pirko <jpirko@...hat.com>
>Date:   Thu Jul 30 01:06:12 2009 +0000
>
>    net: restore the original spinlock to protect unicast list
>
>    There is a path when an assetion in dev_unicast_sync() appears.
>
>    igmp6_group_added -> dev_mc_add -> __dev_set_rx_mode ->
>    -> vlan_dev_set_rx_mode -> dev_unicast_sync
>
>    Therefore we cannot protect this list with rtnl. This patch restores the
>    original protecting this list with spinlock.
>
>    Signed-off-by: Jiri Pirko <jpirko@...hat.com>
>    Tested-by: Meelis Roos <mroos@...ux.ee>
>    Signed-off-by: David S. Miller <davem@...emloft.net>
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