netdev - Re: [PATCH net-next 03/10] vxlan: move IGMP join/leave to work queue

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Date:	Wed, 5 Jun 2013 10:29:10 +0300
From:	Mike Rapoport <mike.rapoport@...ellosystems.com>
To:	Cong Wang <xiyou.wangcong@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH net-next 03/10] vxlan: move IGMP join/leave to work queue

On Wed, Jun 5, 2013 at 9:47 AM, Cong Wang <xiyou.wangcong@...il.com> wrote:
> On Wed, 05 Jun 2013 at 04:24 GMT, Stephen Hemminger <stephen@...workplumber.org> wrote:
>> Do join/leave from work queue to avoid lock inversion problems
>> between normal socket and RTNL. The code comes out cleaner
>> as well.
>>
>> Uses Cong Wang's suggestion to turn refcnt into a real atomic
>> since now need to handle case where last use of socket is IGMP
>> worker.
>>
>> Also fixes race where vxlan_stop could be called after
>> device was deleted on module removal. The call to rtnl_link_unregister
>> would call dellink while vxlan device was still up. Reordering
>> the calls fixes it.
>>
>
> After the first 3 patches applied, I got:
>
> [   55.010954] general protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC
> [   55.013309] CPU: 1 PID: 163 Comm: kworker/1:2 Not tainted
> 3.10.0-rc2+ #1150
> [   55.013309] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007
> [   55.013309] Workqueue: events vxlan_igmp_work

I think the problem happens because vxlan_dellink does
unregister_netdevice_queue and then immediately calls
vxlan_sock_release and thus vs_sock is released before igmp_work
starts

> [   55.013309] task: ffff880070eac900 ti: ffff8800716d4000 task.ti:
> ffff8800716d4000
> [   55.013309] RIP: 0010:[<ffffffff815df704>]  [<ffffffff815df704>]
> vxlan_sock_release+0x25/0x55
> [   55.013309] RSP: 0018:ffff8800716d5cf8  EFLAGS: 00010246
> [   55.013309] RAX: 0000000000000000 RBX: ffff88006fd7c000 RCX:
> 0000000ccee84d06
> [   55.013309] RDX: dead000000200200 RSI: ffff880070ead048 RDI:
> ffff88006fd7c070
> [   55.013309] RBP: ffff8800716d5d08 R08: 0000000000000000 R09:
> ffff8800716d5c48
> [   55.013309] R10: 000000000000b6c4 R11: 000000000000b163 R12:
> ffff88006ebb7400
> [   55.013309] R13: ffff88006fd7c000 R14: ffff8800723b4520 R15:
> 0000000000000000
> [   55.013309] FS:  0000000000000000(0000) GS:ffff88007f800000(0000)
> knlGS:0000000000000000
> [   55.013309] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> [   55.013309] CR2: 00007fa99dc0a000 CR3: 0000000070c17000 CR4:
> 00000000000006e0
> [   55.013309] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
> 0000000000000000
> [   55.013309] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7:
> 0000000000000400
> [   55.013309] Stack:
> [   55.013309]  ffff880070eac900 ffff880070fc0b58 ffff8800716d5d48
> ffffffff815e0a73
> [   55.013309]  080808e0716d5d28 0000000f00000000 ffff8800714ef008
> ffff880070fc0b58
> [   55.013309]  ffff88007f9d6200 ffff88007f9d38c0 ffff8800716d5de8
> ffffffff8106872f
> [   55.013309] Call Trace:
> [   55.013309]  [<ffffffff815e0a73>] vxlan_igmp_work+0xa8/0xcf
> [   55.013309]  [<ffffffff8106872f>] process_one_work+0x240/0x408
> [   55.013309]  [<ffffffff81068662>] ? process_one_work+0x173/0x408
> [   55.013309]  [<ffffffff81068c82>] worker_thread+0x15d/0x1f1
> [   55.013309]  [<ffffffff81068b25>] ? rescuer_thread+0x1ff/0x1ff
> [   55.013309]  [<ffffffff81070c19>] kthread+0xb1/0xb9
> [   55.013309]  [<ffffffff81070b68>] ? freezing+0x17/0x17
> [   55.013309]  [<ffffffff81976bdc>] ret_from_fork+0x7c/0xb0
> [   55.013309]  [<ffffffff81070b68>] ? freezing+0x17/0x17
>
> --
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--
Sincerely yours,
Mike.
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