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SubjectRe: [PATCH 1/1] Drivers: hv: vmbus: Fix rescind handling issues
Date
Stephen Hemminger <stephen@networkplumber.org> writes:

> On Sep 15, 2017 11:01 AM, "KY Srinivasan" <kys@microsoft.com> wrote:
>
> > Vitaly Kuznetsov <vkuznets@redhat.com> writes:
> >
> > >
> > > I'm seeing the same issue, reverting the offending
> > >
> > > commit 6f3d791f300618caf82a2be0c27456edd76d5164
> > > Author: K. Y. Srinivasan <kys@microsoft.com>
> > > Date: Fri Aug 11 10:03:59 2017 -0700
> > >
> > > Drivers: hv: vmbus: Fix rescind handling issues
> > >
> > > which made it upstream helps. Did you guys do some investigation here?
> > > In case not I can take a look next week.
> >
> > Sorry, I have to resend - K.Y.'s kys@exchange.microsoft.com doesn't
> > accept mail from me :-(
>
> I think this turned out to be a bug in netvsc - Stephen can elaborate. I think the fix
> has been submitted upstream as well.
>
> K. Y
> >
> > --
> > Vitaly
>
> It turned out that subchannel call back is run from primary channel call back, and was deadlocking waiting for vmbus open.
>
> Original code had broken wait for sub channels.
> The first for that induced this bug.
>
> The resolution is in latest network driver was to bring up sub channels from work queue

This is a bit confusing, in case you mean

commit 8195b1396ec86dddbba443c74b2188b423556c74
Author: Stephen Hemminger <stephen@networkplumber.org>
Date: Wed Sep 6 13:53:05 2017 -0700

hv_netvsc: fix deadlock on hotplug

is supposed to fix the issue. I'm testing the latest net-next which has
it:

$ git log --oneline drivers/net/hyperv/
5023a6db7319 netvsc: increase default receive buffer size
8f2bb1de7334 hv_netvsc: avoid unnecessary wakeups on subchannel creation
8195b1396ec8 hv_netvsc: fix deadlock on hotplug
db3cd7af9d0f hv_netvsc: Fix the channel limit in netvsc_set_rxfh()
06be580ac7b6 hv_netvsc: Simplify the limit check in netvsc_set_channels()
...

and when I do

# ip link set dev eth0 mtu 1400
# ip link set dev eth0 mtu 1500
(actually, you can do mtu change just once the deadlock has already
happened, doing it twice just reveals the issue faster - it will hang
permanently trying to get rtnl lock which is already taken)

The log is:

[ 248.800089] INFO: task kworker/u480:0:5 blocked for more than 120 seconds.
[ 248.804065] Not tainted 4.14.0-rc1 #63
[ 248.806486] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 248.810879] kworker/u480:0 D 0 5 2 0x80000000
[ 248.814225] Workqueue: netns cleanup_net
[ 248.816745] Call Trace:
[ 248.818286] __schedule+0x1d5/0x790
[ 248.820398] ? sched_clock+0x9/0x10
[ 248.822297] ? select_idle_sibling+0x24/0x420
[ 248.824883] schedule+0x31/0x80
[ 248.826835] schedule_preempt_disabled+0x9/0x10
[ 248.829444] __mutex_lock.isra.1+0x1a3/0x4f0
[ 248.831973] ? sched_clock_cpu+0x5d/0xb0
[ 248.834300] __mutex_lock_slowpath+0xe/0x10
[ 248.836869] ? __mutex_lock_slowpath+0xe/0x10
[ 248.839488] mutex_lock+0x2a/0x30
[ 248.841378] rtnl_lock+0x10/0x20
[ 248.843431] cleanup_net+0x94/0x2e0
[ 248.845479] process_one_work+0x193/0x390
[ 248.847838] worker_thread+0x48/0x3c0
[ 248.850121] kthread+0x120/0x140
[ 248.851927] ? process_one_work+0x390/0x390
[ 248.854425] ? kthread_create_on_node+0x60/0x60
[ 248.856884] ? kthread_create_on_node+0x60/0x60
[ 248.859585] ret_from_fork+0x25/0x30
[ 248.861581] INFO: task kworker/9:2:374 blocked for more than 120 seconds.
[ 248.865286] Not tainted 4.14.0-rc1 #63
[ 248.867655] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 248.872135] kworker/9:2 D 0 374 2 0x80000000
[ 248.875175] Workqueue: events rndis_set_subchannel [hv_netvsc]
[ 248.878473] Call Trace:
[ 248.879825] __schedule+0x1d5/0x790
[ 248.882122] schedule+0x31/0x80
[ 248.884160] rndis_set_subchannel+0x186/0x1e0 [hv_netvsc]
[ 248.887741] ? finish_wait+0x80/0x80
[ 248.889960] process_one_work+0x193/0x390
[ 248.892349] worker_thread+0x48/0x3c0
[ 248.894484] kthread+0x120/0x140
[ 248.896364] ? process_one_work+0x390/0x390
[ 248.898756] ? kthread_create_on_node+0x60/0x60
[ 248.901229] ret_from_fork+0x25/0x30
[ 248.903180] INFO: task hypervkvpd:656 blocked for more than 120 seconds.
[ 248.907120] Not tainted 4.14.0-rc1 #63
[ 248.909966] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 248.914387] hypervkvpd D 0 656 1 0x00000000
[ 248.917618] Call Trace:
[ 248.919119] __schedule+0x1d5/0x790
[ 248.921343] schedule+0x31/0x80
[ 248.924454] schedule_preempt_disabled+0x9/0x10
[ 248.927792] __mutex_lock.isra.1+0x1a3/0x4f0
[ 248.930951] __mutex_lock_slowpath+0xe/0x10
[ 248.934078] ? __mutex_lock_slowpath+0xe/0x10
[ 248.937466] mutex_lock+0x2a/0x30
[ 248.940228] __netlink_dump_start+0x44/0x190
[ 248.943286] rtnetlink_rcv_msg+0x1a2/0x280
[ 248.946237] ? vsnprintf+0xea/0x4d0
[ 248.948888] ? rtnl_getlink+0x1c0/0x1c0
[ 248.951713] ? rtnl_getlink+0x1c0/0x1c0
[ 248.954644] ? rtnl_calcit.isra.26+0x110/0x110
[ 248.958010] netlink_rcv_skb+0x89/0x130
[ 248.960945] rtnetlink_rcv+0x10/0x20
[ 248.963566] netlink_unicast+0x186/0x220
[ 248.966442] netlink_sendmsg+0x2a8/0x3a0
[ 248.969369] sock_sendmsg+0x33/0x40
[ 248.971955] SYSC_sendto+0x13f/0x180
[ 248.974552] ? SYSC_getsockname+0xc7/0xe0
[ 248.977393] ? fd_install+0x20/0x30
[ 248.980044] ? sock_map_fd+0x3f/0x60
[ 248.982995] SyS_sendto+0x9/0x10
[ 248.986106] entry_SYSCALL_64_fastpath+0x1a/0xa5
[ 248.989785] RIP: 0033:0x7f544421f0d3
[ 248.992576] RSP: 002b:00007ffcb8a81dc8 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
[ 248.997458] RAX: ffffffffffffffda RBX: 000000000000000a RCX: 00007f544421f0d3
[ 249.002140] RDX: 0000000000000014 RSI: 00007ffcb8a82e20 RDI: 000000000000000a
[ 249.006863] RBP: 00007ffcb8a84e50 R08: 00007ffcb8a82e00 R09: 000000000000000c
[ 249.011590] R10: 0000000000000000 R11: 0000000000000246 R12: 00005598e3c4d963
[ 249.016558] R13: 00005598e3bb1110 R14: 00005598e3c4d8c0 R15: 0000000000000011
[ 249.021481] INFO: task ip:1004 blocked for more than 120 seconds.
[ 249.025703] Not tainted 4.14.0-rc1 #63
[ 249.028713] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 249.039417] ip D 0 1004 938 0x00000000
[ 249.043418] Call Trace:
[ 249.045633] __schedule+0x1d5/0x790
[ 249.048335] schedule+0x31/0x80
[ 249.050795] schedule_preempt_disabled+0x9/0x10
[ 249.054109] __mutex_lock.isra.1+0x1a3/0x4f0
[ 249.057251] ? security_capable+0x43/0x60
[ 249.060188] __mutex_lock_slowpath+0xe/0x10
[ 249.063299] ? __netlink_ns_capable+0x36/0x40
[ 249.066416] ? __mutex_lock_slowpath+0xe/0x10
[ 249.069520] mutex_lock+0x2a/0x30
[ 249.072032] rtnetlink_rcv_msg+0x1cb/0x280
[ 249.075189] ? rtnl_calcit.isra.26+0x110/0x110
[ 249.079047] netlink_rcv_skb+0x89/0x130
[ 249.082209] rtnetlink_rcv+0x10/0x20
[ 249.085369] netlink_unicast+0x186/0x220
[ 249.088767] netlink_sendmsg+0x2a8/0x3a0
[ 249.091777] sock_sendmsg+0x33/0x40
[ 249.094353] SYSC_sendto+0x13f/0x180
[ 249.096938] ? handle_mm_fault+0x65/0xf0
[ 249.099824] ? __do_page_fault+0x250/0x4a0
[ 249.102817] SyS_sendto+0x9/0x10
[ 249.105240] entry_SYSCALL_64_fastpath+0x1a/0xa5
[ 249.108489] RIP: 0033:0x7f972cc28f7d
[ 249.111176] RSP: 002b:00007ffed31097e8 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
[ 249.115958] RAX: ffffffffffffffda RBX: 000000000066fc90 RCX: 00007f972cc28f7d
[ 249.120548] RDX: 0000000000000020 RSI: 00007ffed3109800 RDI: 0000000000000003
[ 249.125439] RBP: 0000000000000005 R08: 0000000000000000 R09: 0000000000000000
[ 249.130397] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000006
[ 249.135432] R13: 00007ffed3109ed0 R14: 00007ffed3109ed8 R15: 00007ffed310ae1f

Reverting 6f3d791f300618caf82a2be0c27456edd76d5164 still helps. Or do
you mean some other fix which is not yet in net-next?

--
Vitaly

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