On Mon, May 21, 2012 at 06:03:43PM +0000, 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: > > * 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". > > Bruce, how is this supposed to be working? Yeah, I don't know. For the nfs callback case, it looks like you've just got a single callback service shared across all namespaces, and all you want to do is destroy that whole thing on last put; or is it more complicated than that? For the other servers at least the per-net and global parts of the server seem too entangled. That's unavoidable to some degree since we're sharing threads among the namespaces. But maybe separate structures for the per-namespace and global pieces would help. At a minimum the per-namespace piece would keep a count of the users in that namespace. To make the shutdown race-free I think we also need a way to wait for all threads processing requests in that namespace, which I don't see that we have yet. --b. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
