Messages in this thread | | | Date | Mon, 24 Aug 2009 16:18:28 +0100 | Subject | Re: [2.6.31-rc7] NFS4 client manager kthread spinning... | From | Daniel J Blueman <> |
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Hi Trond,
On Mon, Aug 17, 2009 at 2:53 PM, Daniel J Blueman<daniel.blueman@gmail.com> wrote: > Hi Trond, > > On Mon, Aug 17, 2009 at 2:12 PM, Trond > Myklebust<Trond.Myklebust@netapp.com> wrote: >> On Sun, 2009-08-16 at 23:40 +0100, Daniel J Blueman wrote: >>> After losing and regaining ethernet link a few times with 2.6.31-rc5 >>> [1], I've hit an oops in the NFS4 client manager kthread [2] on my >>> client with NFS4 homedir mount. >>> >>> Do you have a frequent test-case for when the client's manager kthread >>> gets invoked (with and without succeeding callbacks, due to eg a >>> firewall)? Server here is unpatched 2.6.30-rc6; I recall seeing >>> problems when the manager kthread gets invoked, across quite a few >>> kernel releases, just wasn't lucky enough to catch an oops. >>> >>> Oppsing in allow_signal() suggests task state corruption perhaps? I'm >>> downloading the debug kernel to match up the disassembly and line >>> numbers, if that helps? This time, the client had no firewall (but >>> have seen other issues when the callback has failed due to the >>> firewall). >> >> Those aren't Oopses. They are 'soft lockup' warnings. Basically, they're >> saying that the CPU is getting stuck waiting for a spin lock or a mutex. >> >> In this case, it is probably the fact that the state manager is going >> nuts trying to recover, while the connection to the server keeps coming >> up and going down. >> >> What does 'netstat -t' say when you get into this situation? > > Whoops; it's true the stack-trace comes from the soft-lockup detector. > > There was a single 200s link excursion, but the client didn't recover > as locks are held and never released it seems; I observe the > '192.168.1.250-m' NFS4 manager kthread being created and not going > away, despite IP connectivity with the server being fine after. > > I'll reproduce it with stock 2.6.31-rc6 on the client and get 'netstat > -t' output.
(subject line updated)
After further analysis, I see that NFS services do correctly recover after the link excursion, however we see: - link is restored - the manager kthread gets created, does some work - we see lock reclamation fail [1] - after a short while, NFS read()s continue, all is good - the manager kthread spins indefinitely [2, 3] on (struct rpc_wait_queue)queue->lock with spin_lock_bh() [see rpc_wake_up]
This seems reproducible with various kernel debugging enabled (perhaps suggesting use-after-free via the lock being reinitialised/poisoned?).
Let me know if anything else may help track this down (config, stack frame resolution etc). I'll take a deeper look if I get time in a couple of weeks, but alas it may be after 2.6.31 is released. NFS+RPC debugging (taken at a different time than [1]) at http://quora.org/hive/nfs-manager-spin.bz2 .
Thanks, Daniel
--- [1]
[ 1692.147184] e1000e: eth0 NIC Link is Down [ 1894.417242] nfs: server x1 not responding, still trying [ 1904.715032] e1000e: eth0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX/TX [ 1957.423232] nfs: server x1 OK [ 1957.481925] nfs4_reclaim_open_state: Lock reclaim failed!
--- [2]
$ ps -ef <snip> UID PID PPID C STIME TTY TIME CMD root 5028 2 99 22:59 ? 00:00:09 [192.168.10.250-]
--- [3]
192.168.10.25 R running task 4040 5107 2 0x00000000
ffffffff826c5470 00000000000002fb ffff88014b215d90 ffffffff810a2321
ffffffff8168f99e 0000000000024390 0000000100000001 ffff880100000000
0000000100000001 0000000000000001 0000000000000000 ffff8801451b54e8
Call Trace:
[<ffffffff810a2321>] __lock_acquire+0x2d1/0x1240
[<ffffffff8168f99e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
[<ffffffff81693fa2>] ? sub_preempt_count+0x142/0x150
[<ffffffff810a33ae>] lock_acquire+0x11e/0x170
[<ffffffff8163f718>] ? rpc_wake_up+0x18/0xa0
[<ffffffff81693fa2>] ? sub_preempt_count+0x142/0x150
[<ffffffff8168fee6>] ? _spin_lock_bh+0x46/0x80
[<ffffffff8163f718>] ? rpc_wake_up+0x18/0xa0
[<ffffffff8124ff26>] ? nfs4_clear_state_manager_bit+0x36/0x40
[<ffffffff812515a8>] ? nfs4_run_state_manager+0x378/0x500
[<ffffffff81251230>] ? nfs4_run_state_manager+0x0/0x500
[<ffffffff81088946>] ? kthread+0xa6/0xc0
[<ffffffff8100d71a>] ? child_rip+0xa/0x20
[<ffffffff8100d054>] ? restore_args+0x0/0x30
[<ffffffff810888a0>] ? kthread+0x0/0xc0
[<ffffffff8100d710>] ? child_rip+0x0/0x20 -- Daniel J Blueman
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