Re: 3.4. sunrpc oops during shutdown

[Stanislav Kinsbursky <skinsbursky@parallels.com>]

On 21.05.2012 22:03, Myklebust, Trond wrote:
> On Mon, 2012-05-21 at 13:14 -0400, Dave Jones wrote:
>> Tried to shutdown a machine, got this, and a bunch of hung processes.
>> There was one NFS mount mounted at the time.
>>
>> 	Dave
>>
>> BUG: unable to handle kernel NULL pointer dereference at 0000000000000028
>> IP: [<ffffffffa01191df>] svc_destroy+0x1f/0x140 [sunrpc]
>> PGD 1434c4067 PUD 144964067 PMD 0
>> Oops: 0000 [#1] PREEMPT SMP
>> CPU 4
>> Modules linked in: ip6table_filter(-) ip6_tables nfsd nfs fscache auth_rpcgss nfs_acl lockd ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6
>>
>> Pid: 6946, comm: ntpd Not tainted 3.4.0+ #13
>> RIP: 0010:[<ffffffffa01191df>]  [<ffffffffa01191df>] svc_destroy+0x1f/0x140 [sunrpc]
>> RSP: 0018:ffff880143c65c48  EFLAGS: 00010286
>> RAX: 0000000000000000 RBX: ffff880142cd41a0 RCX: 0000000000000006
>> RDX: 0000000000000040 RSI: ffff880143105028 RDI: ffff880142cd41a0
>> RBP: ffff880143c65c58 R08: 0000000000000000 R09: 0000000000000001
>> R10: 0000000000000000 R11: 0000000000000000 R12: ffff88013bc5a148
>> R13: ffff880140981658 R14: ffff880142cd41a0 R15: ffff880146c88000
>> FS:  00007fdc0382a740(0000) GS:ffff880149400000(0000) knlGS:0000000000000000
>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: 0000000000000028 CR3: 0000000036cbb000 CR4: 00000000001407e0
>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
>> Process ntpd (pid: 6946, threadinfo ffff880143c64000, task ffff880143104940)
>> Stack:
>>   ffff880140981660 ffff88013bc5a148 ffff880143c65c88 ffffffffa01193a6
>>   0000000000000000 ffff88013e566020 ffff88013e565f28 ffff880146ee6ac0
>>   ffff880143c65ca8 ffffffffa024f403 ffff880143c65ca8 ffff880143d3a4f8
>> Call Trace:
>>   [<ffffffffa01193a6>] svc_exit_thread+0xa6/0xb0 [sunrpc]
>>   [<ffffffffa024f403>] nfs_callback_down+0x53/0x90 [nfs]
>>   [<ffffffffa021642e>] nfs_free_client+0xfe/0x120 [nfs]
>>   [<ffffffffa02185df>] nfs_put_client+0x29f/0x420 [nfs]
>>   [<ffffffffa02184e0>] ? nfs_put_client+0x1a0/0x420 [nfs]
>>   [<ffffffffa021962f>] nfs_free_server+0x16f/0x2e0 [nfs]
>>   [<ffffffffa02194e3>] ? nfs_free_server+0x23/0x2e0 [nfs]
>>   [<ffffffffa022363c>] nfs4_kill_super+0x3c/0x50 [nfs]
>>   [<ffffffff811ad67c>] deactivate_locked_super+0x3c/0xa0
>>   [<ffffffff811ae29e>] deactivate_super+0x4e/0x70
>>   [<ffffffff811ccba4>] mntput_no_expire+0xb4/0x100
>>   [<ffffffff811ccc16>] mntput+0x26/0x40
>>   [<ffffffff811cd597>] release_mounts+0x77/0x90
>>   [<ffffffff811cefc6>] put_mnt_ns+0x66/0x80
>>   [<ffffffff81078dff>] free_nsproxy+0x1f/0xb0
>>   [<ffffffff8107905e>] switch_task_namespaces+0x5e/0x70
>>   [<ffffffff81079080>] exit_task_namespaces+0x10/0x20
>>   [<ffffffff8104e90e>] do_exit+0x4ee/0xb80
>>   [<ffffffff81639c0a>] ? retint_swapgs+0xe/0x13
>>   [<ffffffff8104f2ef>] do_group_exit+0x4f/0xc0
>>   [<ffffffff8104f377>] sys_exit_group+0x17/0x20
>>   [<ffffffff81641352>] system_call_fastpath+0x16/0x1b
>> Code: 48 8b 5d f0 4c 8b 65 f8 c9 c3 66 90 55 48 89 e5 41 54 53 66 66 66 66 90 65 48 8b 04 25 80 ba 00 00 48 8b 80 50 05 00 00 48 89 fb<4c>  8b 60 28 8b 47 58 85 c0 0f 84 ec 00 00 00 83 e8 01 85 c0 89
>
> Aside from the fact that the current net_namespace is not guaranteed to
> exist when we are called from free_nsproxy, svc_destroy() looks
> seriously broken:

Trond, looks like you are mistaken here.
Any process holds references to all namespaces it belong to (copy_net_ns() 
increase usage counter). And network namespace is released after mount namespace 
in free_nsproxy.

>
>        * On the one hand it is trying to free struct svc_serv (and
>          presumably all structures owned by struct svc_serv).
>        * On the other hand, it tries to pass a parameter to
>          svc_close_net() saying "please don't free structures on my
>          sv_tempsocks, or sv_permsocks list unless they match this net
>          namespace".
>

I've sent patches, which moves svc_shutdown_net() from svc_destroy() ("SUNRPC: 
separate per-net data creation from service").
with this patch set it's assumed, that per-net resources will be created or 
released prior to service creation and destruction.

> Bruce, how is this supposed to be working?
>
> Cheers
>    Trond


-- 
Best regards,
Stanislav Kinsbursky