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Date:   Fri, 4 Sep 2020 16:20:20 -0700
From:   Baptiste Covolato <baptiste@...sta.com>
To:     Michael Chan <michael.chan@...adcom.com>
Cc:     davem@...emloft.net, Netdev <netdev@...r.kernel.org>,
        kuba@...nel.org, David Christensen <drc@...ux.vnet.ibm.com>
Subject: Re: [PATCH net] tg3: Fix soft lockup when tg3_reset_task() fails.

Hi Michael,

On Thu, Sep 3, 2020 at 11:29 AM Michael Chan <michael.chan@...adcom.com> wrote:
> If tg3_reset_task() fails, the device state is left in an inconsistent
> state with IFF_RUNNING still set but NAPI state not enabled.  A
> subsequent operation, such as ifdown or AER error can cause it to
> soft lock up when it tries to disable NAPI state.
>
> Fix it by bringing down the device to !IFF_RUNNING state when
> tg3_reset_task() fails.  tg3_reset_task() running from workqueue
> will now call tg3_close() when the reset fails.  We need to
> modify tg3_reset_task_cancel() slightly to avoid tg3_close()
> calling cancel_work_sync() to cancel tg3_reset_task().  Otherwise
> cancel_work_sync() will wait forever for tg3_reset_task() to
> finish.

Thank you for proposing this patch. Unfortunately, it appears to make
things worse on my test setup. The problem is a lot easier to
reproduce, and not related to transmit timeout anymore.

The manifestation of the problem with the new patch starts with a
CmpltTO error on the PCI root port of the CPU:
[11288.471126] tg3 0000:56:00.0: tg3_abort_hw timed out,
TX_MODE_ENABLE will not clear MAC_TX_MODE=ffffffff
[11290.258733] tg3 0000:56:00.0 lc4: No firmware running
[11302.336601] tg3 0000:56:00.0 lc4: Link is down
[11302.336616] pcieport 0000:00:03.0: AER: Uncorrected (Non-Fatal)
error received: 0000:00:03.0
[11302.336621] pcieport 0000:00:03.0: PCIe Bus Error:
severity=Uncorrected (Non-Fatal), type=Transaction Layer, (Requester
ID)
[11302.470089] pcieport 0000:00:03.0:   device [8086:6f08] error
status/mask=00004000/00000000
[11302.570218] pcieport 0000:00:03.0:    [14] CmpltTO                (First)
[11302.651611] pcieport 0000:00:03.0: broadcast error_detected message
[11305.119349] br1: port 4(lc4) entered disabled state
[11305.119443] br1: port 1(lc4.42) entered disabled state
[11305.119696] device lc4 left promiscuous mode
[11305.119697] br1: port 4(lc4) entered disabled state
[11305.143622] device lc4.42 left promiscuous mode
[11305.143626] br1: port 1(lc4.42) entered disabled state
[11305.219623] iommu: Removing device 0000:56:00.0 from group 52
[11305.219672] tg3 0000:61:00.0 lc5: PCI I/O error detected
[11305.345904] tg3 0000:6c:00.0 lc6: PCI I/O error detected
[11305.472089] pcieport 0000:00:03.0: AER: Device recovery failed
[11305.472092] pcieport 0000:00:03.0: AER: Uncorrected (Non-Fatal)
error received: 0000:00:03.0
[11305.472096] pcieport 0000:00:03.0: PCIe Bus Error:
severity=Uncorrected (Non-Fatal), type=Transaction Layer, (Requester
ID)
[11305.472142] pcielw 0000:52:0d.0:pcie204: link down processing complete
[11305.605566] pcieport 0000:00:03.0:   device [8086:6f08] error
status/mask=00004000/00000000
[11305.605568] pcieport 0000:00:03.0:    [14] CmpltTO                (First)
[11305.605578] pcieport 0000:00:03.0: broadcast error_detected message
[11305.787386] tg3 0000:61:00.0 lc5: PCI I/O error detected

Once these PCI errors happen, the kernel is dead locked for any
network operations. We shortly see stack traces of task blocked
doing network configuration operations after that:
[11481.166888] INFO: task ntpd:6107 blocked for more than 120 seconds.
[11481.242021]       Tainted: G           OE     4.19.0-9-2-amd64 #1
Debian 4.19.118-2+deb10u1
[11481.342126] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
disables this message.
[11481.436018] ntpd            D    0  6107      1 0x00000004
[11481.436020] Call Trace:
[11481.436023]  ? __schedule+0x2a2/0x870
[11481.436025]  schedule+0x28/0x80
[11481.436043]  schedule_preempt_disabled+0xa/0x10
[11481.436045]  __mutex_lock.isra.8+0x2b5/0x4a0
[11481.436048]  ? __netlink_lookup+0xcd/0x130
[11481.436049]  __netlink_dump_start+0x56/0x1e0
[11481.436053]  ? rtnl_fill_ifinfo+0xe90/0xe90
[11481.436059]  rtnetlink_rcv_msg+0x22c/0x360
[11481.436065]  ? rtnl_fill_ifinfo+0xe90/0xe90
[11481.436071]  ? rtnl_calcit.isra.33+0x100/0x100
[11481.436076]  netlink_rcv_skb+0x4c/0x120
[11481.436083]  netlink_unicast+0x181/0x210
[11481.436089]  netlink_sendmsg+0x204/0x3d0
[11481.436095]  sock_sendmsg+0x36/0x40
[11481.436097]  __sys_sendto+0xee/0x160
[11481.436100]  ? __sys_socket+0x93/0xe0
[11481.436102]  __x64_sys_sendto+0x24/0x30
[11481.436105]  do_syscall_64+0x53/0x110
[11481.436107]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[11481.436109] RIP: 0033:0x7fe88125aa02
[11481.436113] Code: Bad RIP value.
[11481.436113] RSP: 002b:00007ffdbdcd8950 EFLAGS: 00000293 ORIG_RAX:
000000000000002c
[11481.436115] RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00007fe88125aa02
[11481.436116] RDX: 0000000000000014 RSI: 00007ffdbdcd9a30 RDI: 0000000000000004
[11481.436116] RBP: 0000000000000000 R08: 00007ffdbdcd99f0 R09: 000000000000000c
[11481.436117] R10: 0000000000000000 R11: 0000000000000293 R12: 00007ffdbdcd9a30
[11481.436118] R13: 0000000000000014 R14: 0000000000000000 R15: 00007ffdbdcd99f0

Do you have any idea of where this could be coming from? Is it
possible that this patch introduced a new window where the deadlock
can happen?

Thanks,

--
Baptiste Covolato

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