inconsistent lock state with usbnet/asix usb ethernet and xhci

inconsistent lock state with usbnet/asix usb ethernet and xhci

[Marek Szyprowski]

Hi

I've noticed that USBnet/ASIX AX88772B USB driver produces deplock kernel
warning ("inconsistent lock state") on Chromebook2 Peach-PIT board. No
special activity is needed to reproduce this issue, it happens almost
on every boot. ASIX USB ethernet is connected to XHCI USB host controller
on that board. Is it a known issue? Frankly I have no idea where to look
to fix it. The same adapter connected to EHCI ports on other boards based
on the same SoC works fine without any warnings.

Here are some more information from that board:
# lsusb
Bus 006 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 005 Device 002: ID 0b95:772b ASIX Electronics Corp. AX88772B
Bus 005 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 002: ID 2232:1056 Silicon Motion
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

# lsusb -t
/:  Bus 06.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 5000M
/:  Bus 05.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 480M
     |__ Port 1: Dev 2, If 0, Class=Vendor Specific Class, Driver=asix, 480M
/:  Bus 04.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 5000M
/:  Bus 03.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 480M
/:  Bus 02.Port 1: Dev 1, Class=root_hub, Driver=exynos-ohci/3p, 12M
/:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=exynos-ehci/3p, 480M
     |__ Port 1: Dev 2, If 0, Class=Video, Driver=, 480M
     |__ Port 1: Dev 2, If 1, Class=Video, Driver=, 480M


And the log with mentioned warning:

[   17.768040] ================================
[   17.772239] WARNING: inconsistent lock state
[   17.776511] 4.16.0-rc3-next-20180227-00007-g876c53a7493c #453 Not tainted
[   17.783329] --------------------------------
[   17.787580] inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
[   17.793607] swapper/0/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
[   17.798751]  (&syncp->seq#5){?.-.}, at: [<9b22e5f0>] 
asix_rx_fixup_internal+0x188/0x288
[   17.806790] {IN-HARDIRQ-W} state was registered at:
[   17.811677]   tx_complete+0x100/0x208
[   17.815319]   __usb_hcd_giveback_urb+0x60/0xf0
[   17.819770]   xhci_giveback_urb_in_irq+0xa8/0x240
[   17.824469]   xhci_td_cleanup+0xf4/0x16c
[   17.828367]   xhci_irq+0xe74/0x2240
[   17.831827]   usb_hcd_irq+0x24/0x38
[   17.835343]   __handle_irq_event_percpu+0x98/0x510
[   17.840111]   handle_irq_event_percpu+0x1c/0x58
[   17.844623]   handle_irq_event+0x38/0x5c
[   17.848519]   handle_fasteoi_irq+0xa4/0x138
[   17.852681]   generic_handle_irq+0x18/0x28
[   17.856760]   __handle_domain_irq+0x6c/0xe4
[   17.860941]   gic_handle_irq+0x54/0xa0
[   17.864666]   __irq_svc+0x70/0xb0
[   17.867964]   arch_cpu_idle+0x20/0x3c
[   17.871578]   arch_cpu_idle+0x20/0x3c
[   17.875190]   do_idle+0x144/0x218
[   17.878468]   cpu_startup_entry+0x18/0x1c
[   17.882454]   start_kernel+0x394/0x400
[   17.886177] irq event stamp: 161912
[   17.889616] hardirqs last  enabled at (161912): [<7bedfacf>] 
__netdev_alloc_skb+0xcc/0x140
[   17.897893] hardirqs last disabled at (161911): [<d58261d0>] 
__netdev_alloc_skb+0x94/0x140
[   17.904903] exynos5-hsi2c 12ca0000.i2c: tx timeout
[   17.906116] softirqs last  enabled at (161904): [<387102ff>] 
irq_enter+0x78/0x80
[   17.906123] softirqs last disabled at (161905): [<cf4c628e>] 
irq_exit+0x134/0x158
[   17.925722].
[   17.925722] other info that might help us debug this:
[   17.933435]  Possible unsafe locking scenario:
[   17.933435].
[   17.940331]        CPU0
[   17.942488]        ----
[   17.944894]   lock(&syncp->seq#5);
[   17.948274]   <Interrupt>
[   17.950847]     lock(&syncp->seq#5);
[   17.954386].
[   17.954386]  *** DEADLOCK ***
[   17.954386].
[   17.962422] no locks held by swapper/0/0.
[   17.966011].
[   17.966011] stack backtrace:
[   17.971333] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 
4.16.0-rc3-next-20180227-00007-g876c53a7493c #453
[   17.980312] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
[   17.986380] [<c0111548>] (unwind_backtrace) from [<c010dbd8>] 
(show_stack+0x10/0x14)
[   17.994128] [<c010dbd8>] (show_stack) from [<c09bd418>] 
(dump_stack+0x90/0xc8)
[   18.001339] [<c09bd418>] (dump_stack) from [<c017fdf8>] 
(print_usage_bug+0x25c/0x2cc)
[   18.009161] [<c017fdf8>] (print_usage_bug) from [<c017c14c>] 
(mark_lock+0x290/0x698)
[   18.014952] exynos5-hsi2c 12ca0000.i2c: tx timeout
[   18.016899] [<c017c14c>] (mark_lock) from [<c017c9a8>] 
(__lock_acquire+0x454/0x1850)
[   18.029449] [<c017c9a8>] (__lock_acquire) from [<c017e6e0>] 
(lock_acquire+0xc8/0x2b8)
[   18.037272] [<c017e6e0>] (lock_acquire) from [<c05be98c>] 
(usbnet_skb_return+0x7c/0x1a0)
[   18.045356] [<c05be98c>] (usbnet_skb_return) from [<c05b185c>] 
(asix_rx_fixup_internal+0x188/0x288)
[   18.054420] [<c05b185c>] (asix_rx_fixup_internal) from [<c05bfe40>] 
(usbnet_bh+0xf8/0x2e4)
[   18.062694] [<c05bfe40>] (usbnet_bh) from [<c012d6b4>] 
(tasklet_action+0x8c/0x13c)
[   18.070259] [<c012d6b4>] (tasklet_action) from [<c0102214>] 
(__do_softirq+0xd4/0x6d4)
[   18.078089] [<c0102214>] (__do_softirq) from [<c012cf34>] 
(irq_exit+0x134/0x158)
[   18.085480] [<c012cf34>] (irq_exit) from [<c018c444>] 
(__handle_domain_irq+0x70/0xe4)
[   18.093314] [<c018c444>] (__handle_domain_irq) from [<c046400c>] 
(gic_handle_irq+0x54/0xa0)
[   18.101670] [<c046400c>] (gic_handle_irq) from [<c01019f0>] 
(__irq_svc+0x70/0xb0)
[   18.109163] Exception stack(0xc0f01eb8 to 0xc0f01f00)
[   18.114202] 1ea0: 00000001 00000001
[   18.122397] 1ec0: 00000000 c0f0ba80 eef3a540 eef3a540 ee8d2700 
c0f088b4 00000402 c09d23e0
[   18.124980] exynos5-hsi2c 12ca0000.i2c: tx timeout
[   18.130611] 1ee0: c0f0ba80 c0f01f4c 00000000 c0f01f08 c017ea54 
c09d92d4 20000013 ffffffff
[   18.135504] cpu cpu0: _set_opp_voltage: failed to set voltage 
(1250000 1250000 1250000 mV): -110
[   18.143690] [<c01019f0>] (__irq_svc) from [<c09d92d4>] 
(_raw_spin_unlock_irq+0x28/0x5c)
[   18.152671] cpufreq: __target_index: Failed to change cpu frequency: -110
[   18.160683] [<c09d92d4>] (_raw_spin_unlock_irq) from [<c0152684>] 
(finish_task_switch+0xb4/0x254)
[   18.160696] [<c0152684>] (finish_task_switch) from [<c09d23e0>] 
(__schedule+0x290/0xb10)
[   18.160704] [<c09d23e0>] (__schedule) from [<c09d3134>] 
(schedule_idle+0x2c/0x78)
[   18.160711] [<c09d3134>] (schedule_idle) from [<c01703a0>] 
(cpu_startup_entry+0x18/0x1c)
[   18.200726] [<c01703a0>] (cpu_startup_entry) from [<c0e00c74>] 
(start_kernel+0x394/0x400)

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

Re: inconsistent lock state with usbnet/asix usb ethernet and xhci

[Oliver Neukum]

Am Dienstag, den 27.02.2018, 08:26 +0100 schrieb Marek Szyprowski:

Hi,

> I've noticed that USBnet/ASIX AX88772B USB driver produces deplock kernel
> warning ("inconsistent lock state") on Chromebook2 Peach-PIT board. No

Is that 32 bit?

> special activity is needed to reproduce this issue, it happens almost
> on every boot. ASIX USB ethernet is connected to XHCI USB host controller
> on that board. Is it a known issue? Frankly I have no idea where to look

No, it is not known.

> to fix it. The same adapter connected to EHCI ports on other boards based
> on the same SoC works fine without any warnings.

Odd.

> And the log with mentioned warning:
> 
> [   17.768040] ================================
> [   17.772239] WARNING: inconsistent lock state
> [   17.776511] 4.16.0-rc3-next-20180227-00007-g876c53a7493c #453 Not tainted
> [   17.783329] --------------------------------
> [   17.787580] inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
> [   17.793607] swapper/0/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
> [   17.798751]  (&syncp->seq#5){?.-.}, at: [<9b22e5f0>] 
> asix_rx_fixup_internal+0x188/0x288

Looks like this triggers (in usbnet):

        u64_stats_update_begin(&stats64->syncp);
        stats64->rx_packets++;
        stats64->rx_bytes += skb->len;
        u64_stats_update_end(&stats64->syncp);

That I considered to be called under lock.
Could you comment this out for testing?

	Regards
		Oliver

Re: inconsistent lock state with usbnet/asix usb ethernet and xhci

[Marek Szyprowski]

Hi Oliver,

On 2018-02-27 11:37, Oliver Neukum wrote:
> Am Dienstag, den 27.02.2018, 08:26 +0100 schrieb Marek Szyprowski:
>
>> I've noticed that USBnet/ASIX AX88772B USB driver produces deplock kernel
>> warning ("inconsistent lock state") on Chromebook2 Peach-PIT board. No
> Is that 32 bit?

Yes. ARM 32bit. Exynos5420 SoC (4 x CortexA15 + 4 x CortexA7 big.LITTLE 
CPUs).

>> special activity is needed to reproduce this issue, it happens almost
>> on every boot. ASIX USB ethernet is connected to XHCI USB host controller
>> on that board. Is it a known issue? Frankly I have no idea where to look
> No, it is not known.
>
>> to fix it. The same adapter connected to EHCI ports on other boards based
>> on the same SoC works fine without any warnings.
> Odd.
>
>> And the log with mentioned warning:
>>
>> [   17.768040] ================================
>> [   17.772239] WARNING: inconsistent lock state
>> [   17.776511] 4.16.0-rc3-next-20180227-00007-g876c53a7493c #453 Not tainted
>> [   17.783329] --------------------------------
>> [   17.787580] inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
>> [   17.793607] swapper/0/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
>> [   17.798751]  (&syncp->seq#5){?.-.}, at: [<9b22e5f0>]
>> asix_rx_fixup_internal+0x188/0x288
> Looks like this triggers (in usbnet):
>
>          u64_stats_update_begin(&stats64->syncp);
>          stats64->rx_packets++;
>          stats64->rx_bytes += skb->len;
>          u64_stats_update_end(&stats64->syncp);
>
> That I considered to be called under lock.
> Could you comment this out for testing?

Yes, commenting this out indeed hides the deplock warning.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

Re: inconsistent lock state with usbnet/asix usb ethernet and xhci

[Eric Dumazet]

On Tue, 2018-02-27 at 08:26 +0100, Marek Szyprowski wrote:
> Hi
> 
> I've noticed that USBnet/ASIX AX88772B USB driver produces deplock kernel
> warning ("inconsistent lock state") on Chromebook2 Peach-PIT board. No
> special activity is needed to reproduce this issue, it happens almost
> on every boot. ASIX USB ethernet is connected to XHCI USB host controller
> on that board. Is it a known issue? Frankly I have no idea where to look
> to fix it. The same adapter connected to EHCI ports on other boards based
> on the same SoC works fine without any warnings.
> 
> Here are some more information from that board:
> # lsusb
> Bus 006 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
> Bus 005 Device 002: ID 0b95:772b ASIX Electronics Corp. AX88772B
> Bus 005 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
> Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
> Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
> Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
> Bus 001 Device 002: ID 2232:1056 Silicon Motion
> Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
> 
> # lsusb -t
> /:  Bus 06.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 5000M
> /:  Bus 05.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 480M
>      |__ Port 1: Dev 2, If 0, Class=Vendor Specific Class, Driver=asix, 480M
> /:  Bus 04.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 5000M
> /:  Bus 03.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 480M
> /:  Bus 02.Port 1: Dev 1, Class=root_hub, Driver=exynos-ohci/3p, 12M
> /:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=exynos-ehci/3p, 480M
>      |__ Port 1: Dev 2, If 0, Class=Video, Driver=, 480M
>      |__ Port 1: Dev 2, If 1, Class=Video, Driver=, 480M
> 
> 
> And the log with mentioned warning:
> 
> [   17.768040] ================================
> [   17.772239] WARNING: inconsistent lock state
> [   17.776511] 4.16.0-rc3-next-20180227-00007-g876c53a7493c #453 Not tainted
> [   17.783329] --------------------------------
> [   17.787580] inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
> [   17.793607] swapper/0/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
> [   17.798751]  (&syncp->seq#5){?.-.}, at: [<9b22e5f0>] 
> asix_rx_fixup_internal+0x188/0x288
> [   17.806790] {IN-HARDIRQ-W} state was registered at:
> [   17.811677]   tx_complete+0x100/0x208
> [   17.815319]   __usb_hcd_giveback_urb+0x60/0xf0
> [   17.819770]   xhci_giveback_urb_in_irq+0xa8/0x240
> [   17.824469]   xhci_td_cleanup+0xf4/0x16c
> [   17.828367]   xhci_irq+0xe74/0x2240
> [   17.831827]   usb_hcd_irq+0x24/0x38
> [   17.835343]   __handle_irq_event_percpu+0x98/0x510
> [   17.840111]   handle_irq_event_percpu+0x1c/0x58
> [   17.844623]   handle_irq_event+0x38/0x5c
> [   17.848519]   handle_fasteoi_irq+0xa4/0x138
> [   17.852681]   generic_handle_irq+0x18/0x28
> [   17.856760]   __handle_domain_irq+0x6c/0xe4
> [   17.860941]   gic_handle_irq+0x54/0xa0
> [   17.864666]   __irq_svc+0x70/0xb0
> [   17.867964]   arch_cpu_idle+0x20/0x3c
> [   17.871578]   arch_cpu_idle+0x20/0x3c
> [   17.875190]   do_idle+0x144/0x218
> [   17.878468]   cpu_startup_entry+0x18/0x1c
> [   17.882454]   start_kernel+0x394/0x400
> [   17.886177] irq event stamp: 161912
> [   17.889616] hardirqs last  enabled at (161912): [<7bedfacf>] 
> __netdev_alloc_skb+0xcc/0x140
> [   17.897893] hardirqs last disabled at (161911): [<d58261d0>] 
> __netdev_alloc_skb+0x94/0x140
> [   17.904903] exynos5-hsi2c 12ca0000.i2c: tx timeout
> [   17.906116] softirqs last  enabled at (161904): [<387102ff>] 
> irq_enter+0x78/0x80
> [   17.906123] softirqs last disabled at (161905): [<cf4c628e>] 
> irq_exit+0x134/0x158
> [   17.925722].
> [   17.925722] other info that might help us debug this:
> [   17.933435]  Possible unsafe locking scenario:
> [   17.933435].
> [   17.940331]        CPU0
> [   17.942488]        ----
> [   17.944894]   lock(&syncp->seq#5);
> [   17.948274]   <Interrupt>
> [   17.950847]     lock(&syncp->seq#5);
> [   17.954386].
> [   17.954386]  *** DEADLOCK ***
> [   17.954386].
> [   17.962422] no locks held by swapper/0/0.
> [   17.966011].
> [   17.966011] stack backtrace:
> [   17.971333] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 
> 4.16.0-rc3-next-20180227-00007-g876c53a7493c #453
> [   17.980312] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
> [   17.986380] [<c0111548>] (unwind_backtrace) from [<c010dbd8>] 
> (show_stack+0x10/0x14)
> [   17.994128] [<c010dbd8>] (show_stack) from [<c09bd418>] 
> (dump_stack+0x90/0xc8)
> [   18.001339] [<c09bd418>] (dump_stack) from [<c017fdf8>] 
> (print_usage_bug+0x25c/0x2cc)
> [   18.009161] [<c017fdf8>] (print_usage_bug) from [<c017c14c>] 
> (mark_lock+0x290/0x698)
> [   18.014952] exynos5-hsi2c 12ca0000.i2c: tx timeout
> [   18.016899] [<c017c14c>] (mark_lock) from [<c017c9a8>] 
> (__lock_acquire+0x454/0x1850)
> [   18.029449] [<c017c9a8>] (__lock_acquire) from [<c017e6e0>] 
> (lock_acquire+0xc8/0x2b8)
> [   18.037272] [<c017e6e0>] (lock_acquire) from [<c05be98c>] 
> (usbnet_skb_return+0x7c/0x1a0)
> [   18.045356] [<c05be98c>] (usbnet_skb_return) from [<c05b185c>] 
> (asix_rx_fixup_internal+0x188/0x288)
> [   18.054420] [<c05b185c>] (asix_rx_fixup_internal) from [<c05bfe40>] 
> (usbnet_bh+0xf8/0x2e4)
> [   18.062694] [<c05bfe40>] (usbnet_bh) from [<c012d6b4>] 
> (tasklet_action+0x8c/0x13c)
> [   18.070259] [<c012d6b4>] (tasklet_action) from [<c0102214>] 
> (__do_softirq+0xd4/0x6d4)
> [   18.078089] [<c0102214>] (__do_softirq) from [<c012cf34>] 
> (irq_exit+0x134/0x158)
> [   18.085480] [<c012cf34>] (irq_exit) from [<c018c444>] 
> (__handle_domain_irq+0x70/0xe4)
> [   18.093314] [<c018c444>] (__handle_domain_irq) from [<c046400c>] 
> (gic_handle_irq+0x54/0xa0)
> [   18.101670] [<c046400c>] (gic_handle_irq) from [<c01019f0>] 
> (__irq_svc+0x70/0xb0)
> [   18.109163] Exception stack(0xc0f01eb8 to 0xc0f01f00)
> [   18.114202] 1ea0: 00000001 00000001
> [   18.122397] 1ec0: 00000000 c0f0ba80 eef3a540 eef3a540 ee8d2700 
> c0f088b4 00000402 c09d23e0
> [   18.124980] exynos5-hsi2c 12ca0000.i2c: tx timeout
> [   18.130611] 1ee0: c0f0ba80 c0f01f4c 00000000 c0f01f08 c017ea54 
> c09d92d4 20000013 ffffffff
> [   18.135504] cpu cpu0: _set_opp_voltage: failed to set voltage 
> (1250000 1250000 1250000 mV): -110
> [   18.143690] [<c01019f0>] (__irq_svc) from [<c09d92d4>] 
> (_raw_spin_unlock_irq+0x28/0x5c)
> [   18.152671] cpufreq: __target_index: Failed to change cpu frequency: -110
> [   18.160683] [<c09d92d4>] (_raw_spin_unlock_irq) from [<c0152684>] 
> (finish_task_switch+0xb4/0x254)
> [   18.160696] [<c0152684>] (finish_task_switch) from [<c09d23e0>] 
> (__schedule+0x290/0xb10)
> [   18.160704] [<c09d23e0>] (__schedule) from [<c09d3134>] 
> (schedule_idle+0x2c/0x78)
> [   18.160711] [<c09d3134>] (schedule_idle) from [<c01703a0>] 
> (cpu_startup_entry+0x18/0x1c)
> [   18.200726] [<c01703a0>] (cpu_startup_entry) from [<c0e00c74>] 
> (start_kernel+0x394/0x400)
> 
> Best regards

Please try the attached patch, thanks.

 drivers/net/usb/usbnet.c       |    5 +++--
 include/linux/u64_stats_sync.h |   22 ++++++++++++++++++++++
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index 8a22ff67b0268a588428c61c6a6211e3c6c2a02a..7f5bda0ec9e8520e6db327b713152afdb250255f 100644
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -315,6 +315,7 @@ static void __usbnet_status_stop_force(struct usbnet *dev)
 void usbnet_skb_return (struct usbnet *dev, struct sk_buff *skb)
 {
 	struct pcpu_sw_netstats *stats64 = this_cpu_ptr(dev->stats64);
+	unsigned long flags;
 	int	status;
 
 	if (test_bit(EVENT_RX_PAUSED, &dev->flags)) {
@@ -326,10 +327,10 @@ void usbnet_skb_return (struct usbnet *dev, struct sk_buff *skb)
 	if (skb->protocol == 0)
 		skb->protocol = eth_type_trans (skb, dev->net);
 
-	u64_stats_update_begin(&stats64->syncp);
+	flags = u64_stats_update_begin_irqsave(&stats64->syncp);
 	stats64->rx_packets++;
 	stats64->rx_bytes += skb->len;
-	u64_stats_update_end(&stats64->syncp);
+	u64_stats_update_end_irqrestore(&stats64->syncp, flags);
 
 	netif_dbg(dev, rx_status, dev->net, "< rx, len %zu, type 0x%x\n",
 		  skb->len + sizeof (struct ethhdr), skb->protocol);
diff --git a/include/linux/u64_stats_sync.h b/include/linux/u64_stats_sync.h
index 5bdbd9f49395f883ca2dc5aa0d7bbde11f379063..07ee0f84a46caa9e2b1c446f96009f63b3b99f50 100644
--- a/include/linux/u64_stats_sync.h
+++ b/include/linux/u64_stats_sync.h
@@ -90,6 +90,28 @@ static inline void u64_stats_update_end(struct u64_stats_sync *syncp)
 #endif
 }
 
+static inline unsigned long
+u64_stats_update_begin_irqsave(struct u64_stats_sync *syncp)
+{
+	unsigned long flags = 0;
+
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
+	local_irq_save(flags);
+	write_seqcount_begin(&syncp->seq);
+#endif
+	return flags;
+}
+
+static inline void
+u64_stats_update_end_irqrestore(struct u64_stats_sync *syncp,
+				unsigned long flags)
+{
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
+	write_seqcount_end(&syncp->seq);
+	local_irq_restore(flags);
+#endif
+}
+
 static inline void u64_stats_update_begin_raw(struct u64_stats_sync *syncp)
 {
 #if BITS_PER_LONG==32 && defined(CONFIG_SMP)

Re: inconsistent lock state with usbnet/asix usb ethernet and xhci

[Marek Szyprowski]

Hi Eric,

On 2018-02-27 15:07, Eric Dumazet wrote:
> On Tue, 2018-02-27 at 08:26 +0100, Marek Szyprowski wrote:
>> I've noticed that USBnet/ASIX AX88772B USB driver produces deplock kernel
>> warning ("inconsistent lock state") on Chromebook2 Peach-PIT board. No
>> special activity is needed to reproduce this issue, it happens almost
>> on every boot. ASIX USB ethernet is connected to XHCI USB host controller
>> on that board. Is it a known issue? Frankly I have no idea where to look
>> to fix it. The same adapter connected to EHCI ports on other boards based
>> on the same SoC works fine without any warnings.
>>
>> Here are some more information from that board:
>> # lsusb
>> Bus 006 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
>> Bus 005 Device 002: ID 0b95:772b ASIX Electronics Corp. AX88772B
>> Bus 005 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
>> Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
>> Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
>> Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
>> Bus 001 Device 002: ID 2232:1056 Silicon Motion
>> Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
>>
>> # lsusb -t
>> /:  Bus 06.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 5000M
>> /:  Bus 05.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 480M
>>       |__ Port 1: Dev 2, If 0, Class=Vendor Specific Class, Driver=asix, 480M
>> /:  Bus 04.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 5000M
>> /:  Bus 03.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 480M
>> /:  Bus 02.Port 1: Dev 1, Class=root_hub, Driver=exynos-ohci/3p, 12M
>> /:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=exynos-ehci/3p, 480M
>>       |__ Port 1: Dev 2, If 0, Class=Video, Driver=, 480M
>>       |__ Port 1: Dev 2, If 1, Class=Video, Driver=, 480M
>>
>>
>> And the log with mentioned warning:
>>
>> [   17.768040] ================================
>> [   17.772239] WARNING: inconsistent lock state
>> [   17.776511] 4.16.0-rc3-next-20180227-00007-g876c53a7493c #453 Not tainted
>> [   17.783329] --------------------------------
>> [   17.787580] inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
>> [   17.793607] swapper/0/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
>> [   17.798751]  (&syncp->seq#5){?.-.}, at: [<9b22e5f0>]
>> asix_rx_fixup_internal+0x188/0x288
>> [   17.806790] {IN-HARDIRQ-W} state was registered at:
>> [   17.811677]   tx_complete+0x100/0x208
>> [   17.815319]   __usb_hcd_giveback_urb+0x60/0xf0
>> [   17.819770]   xhci_giveback_urb_in_irq+0xa8/0x240
>> [   17.824469]   xhci_td_cleanup+0xf4/0x16c
>> [   17.828367]   xhci_irq+0xe74/0x2240
>> [   17.831827]   usb_hcd_irq+0x24/0x38
>> [   17.835343]   __handle_irq_event_percpu+0x98/0x510
>> [   17.840111]   handle_irq_event_percpu+0x1c/0x58
>> [   17.844623]   handle_irq_event+0x38/0x5c
>> [   17.848519]   handle_fasteoi_irq+0xa4/0x138
>> [   17.852681]   generic_handle_irq+0x18/0x28
>> [   17.856760]   __handle_domain_irq+0x6c/0xe4
>> [   17.860941]   gic_handle_irq+0x54/0xa0
>> [   17.864666]   __irq_svc+0x70/0xb0
>> [   17.867964]   arch_cpu_idle+0x20/0x3c
>> [   17.871578]   arch_cpu_idle+0x20/0x3c
>> [   17.875190]   do_idle+0x144/0x218
>> [   17.878468]   cpu_startup_entry+0x18/0x1c
>> [   17.882454]   start_kernel+0x394/0x400
>> [   17.886177] irq event stamp: 161912
>> [   17.889616] hardirqs last  enabled at (161912): [<7bedfacf>]
>> __netdev_alloc_skb+0xcc/0x140
>> [   17.897893] hardirqs last disabled at (161911): [<d58261d0>]
>> __netdev_alloc_skb+0x94/0x140
>> [   17.904903] exynos5-hsi2c 12ca0000.i2c: tx timeout
>> [   17.906116] softirqs last  enabled at (161904): [<387102ff>]
>> irq_enter+0x78/0x80
>> [   17.906123] softirqs last disabled at (161905): [<cf4c628e>]
>> irq_exit+0x134/0x158
>> [   17.925722].
>> [   17.925722] other info that might help us debug this:
>> [   17.933435]  Possible unsafe locking scenario:
>> [   17.933435].
>> [   17.940331]        CPU0
>> [   17.942488]        ----
>> [   17.944894]   lock(&syncp->seq#5);
>> [   17.948274]   <Interrupt>
>> [   17.950847]     lock(&syncp->seq#5);
>> [   17.954386].
>> [   17.954386]  *** DEADLOCK ***
>> [   17.954386].
>> [   17.962422] no locks held by swapper/0/0.
>> [   17.966011].
>> [   17.966011] stack backtrace:
>> [   17.971333] CPU: 0 PID: 0 Comm: swapper/0 Not tainted
>> 4.16.0-rc3-next-20180227-00007-g876c53a7493c #453
>> [   17.980312] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
>> [   17.986380] [<c0111548>] (unwind_backtrace) from [<c010dbd8>]
>> (show_stack+0x10/0x14)
>> [   17.994128] [<c010dbd8>] (show_stack) from [<c09bd418>]
>> (dump_stack+0x90/0xc8)
>> [   18.001339] [<c09bd418>] (dump_stack) from [<c017fdf8>]
>> (print_usage_bug+0x25c/0x2cc)
>> [   18.009161] [<c017fdf8>] (print_usage_bug) from [<c017c14c>]
>> (mark_lock+0x290/0x698)
>> [   18.014952] exynos5-hsi2c 12ca0000.i2c: tx timeout
>> [   18.016899] [<c017c14c>] (mark_lock) from [<c017c9a8>]
>> (__lock_acquire+0x454/0x1850)
>> [   18.029449] [<c017c9a8>] (__lock_acquire) from [<c017e6e0>]
>> (lock_acquire+0xc8/0x2b8)
>> [   18.037272] [<c017e6e0>] (lock_acquire) from [<c05be98c>]
>> (usbnet_skb_return+0x7c/0x1a0)
>> [   18.045356] [<c05be98c>] (usbnet_skb_return) from [<c05b185c>]
>> (asix_rx_fixup_internal+0x188/0x288)
>> [   18.054420] [<c05b185c>] (asix_rx_fixup_internal) from [<c05bfe40>]
>> (usbnet_bh+0xf8/0x2e4)
>> [   18.062694] [<c05bfe40>] (usbnet_bh) from [<c012d6b4>]
>> (tasklet_action+0x8c/0x13c)
>> [   18.070259] [<c012d6b4>] (tasklet_action) from [<c0102214>]
>> (__do_softirq+0xd4/0x6d4)
>> [   18.078089] [<c0102214>] (__do_softirq) from [<c012cf34>]
>> (irq_exit+0x134/0x158)
>> [   18.085480] [<c012cf34>] (irq_exit) from [<c018c444>]
>> (__handle_domain_irq+0x70/0xe4)
>> [   18.093314] [<c018c444>] (__handle_domain_irq) from [<c046400c>]
>> (gic_handle_irq+0x54/0xa0)
>> [   18.101670] [<c046400c>] (gic_handle_irq) from [<c01019f0>]
>> (__irq_svc+0x70/0xb0)
>> [   18.109163] Exception stack(0xc0f01eb8 to 0xc0f01f00)
>> [   18.114202] 1ea0: 00000001 00000001
>> [   18.122397] 1ec0: 00000000 c0f0ba80 eef3a540 eef3a540 ee8d2700
>> c0f088b4 00000402 c09d23e0
>> [   18.124980] exynos5-hsi2c 12ca0000.i2c: tx timeout
>> [   18.130611] 1ee0: c0f0ba80 c0f01f4c 00000000 c0f01f08 c017ea54
>> c09d92d4 20000013 ffffffff
>> [   18.135504] cpu cpu0: _set_opp_voltage: failed to set voltage
>> (1250000 1250000 1250000 mV): -110
>> [   18.143690] [<c01019f0>] (__irq_svc) from [<c09d92d4>]
>> (_raw_spin_unlock_irq+0x28/0x5c)
>> [   18.152671] cpufreq: __target_index: Failed to change cpu frequency: -110
>> [   18.160683] [<c09d92d4>] (_raw_spin_unlock_irq) from [<c0152684>]
>> (finish_task_switch+0xb4/0x254)
>> [   18.160696] [<c0152684>] (finish_task_switch) from [<c09d23e0>]
>> (__schedule+0x290/0xb10)
>> [   18.160704] [<c09d23e0>] (__schedule) from [<c09d3134>]
>> (schedule_idle+0x2c/0x78)
>> [   18.160711] [<c09d3134>] (schedule_idle) from [<c01703a0>]
>> (cpu_startup_entry+0x18/0x1c)
>> [   18.200726] [<c01703a0>] (cpu_startup_entry) from [<c0e00c74>]
>> (start_kernel+0x394/0x400)
>>
>> Best regards
> Please try the attached patch, thanks.

Thanks for the patch. It fixes the deplock warning. However IMHO the same
fix should be also applied to complete_tx function for modifying stats64
there:

diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index 7f5bda0ec9e8..d9eea8cfe6cb 100644
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -1249,11 +1249,12 @@ static void tx_complete (struct urb *urb)

         if (urb->status == 0) {
                 struct pcpu_sw_netstats *stats64 = 
this_cpu_ptr(dev->stats64);
+               unsigned long flags;

-               u64_stats_update_begin(&stats64->syncp);
+               flags = u64_stats_update_begin_irqsave(&stats64->syncp);
                 stats64->tx_packets += entry->packets;
                 stats64->tx_bytes += entry->length;
-               u64_stats_update_end(&stats64->syncp);
+ u64_stats_update_end_irqrestore(&stats64->syncp, flags);
         } else {
                 dev->net->stats.tx_errors++;


I've did that and it also works fine without deplock warning.

>   drivers/net/usb/usbnet.c       |    5 +++--
>   include/linux/u64_stats_sync.h |   22 ++++++++++++++++++++++
>   2 files changed, 25 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
> index 8a22ff67b0268a588428c61c6a6211e3c6c2a02a..7f5bda0ec9e8520e6db327b713152afdb250255f 100644
> --- a/drivers/net/usb/usbnet.c
> +++ b/drivers/net/usb/usbnet.c
> @@ -315,6 +315,7 @@ static void __usbnet_status_stop_force(struct usbnet *dev)
>   void usbnet_skb_return (struct usbnet *dev, struct sk_buff *skb)
>   {
>   	struct pcpu_sw_netstats *stats64 = this_cpu_ptr(dev->stats64);
> +	unsigned long flags;
>   	int	status;
>   
>   	if (test_bit(EVENT_RX_PAUSED, &dev->flags)) {
> @@ -326,10 +327,10 @@ void usbnet_skb_return (struct usbnet *dev, struct sk_buff *skb)
>   	if (skb->protocol == 0)
>   		skb->protocol = eth_type_trans (skb, dev->net);
>   
> -	u64_stats_update_begin(&stats64->syncp);
> +	flags = u64_stats_update_begin_irqsave(&stats64->syncp);
>   	stats64->rx_packets++;
>   	stats64->rx_bytes += skb->len;
> -	u64_stats_update_end(&stats64->syncp);
> +	u64_stats_update_end_irqrestore(&stats64->syncp, flags);
>   
>   	netif_dbg(dev, rx_status, dev->net, "< rx, len %zu, type 0x%x\n",
>   		  skb->len + sizeof (struct ethhdr), skb->protocol);
> diff --git a/include/linux/u64_stats_sync.h b/include/linux/u64_stats_sync.h
> index 5bdbd9f49395f883ca2dc5aa0d7bbde11f379063..07ee0f84a46caa9e2b1c446f96009f63b3b99f50 100644
> --- a/include/linux/u64_stats_sync.h
> +++ b/include/linux/u64_stats_sync.h
> @@ -90,6 +90,28 @@ static inline void u64_stats_update_end(struct u64_stats_sync *syncp)
>   #endif
>   }
>   
> +static inline unsigned long
> +u64_stats_update_begin_irqsave(struct u64_stats_sync *syncp)
> +{
> +	unsigned long flags = 0;
> +
> +#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
> +	local_irq_save(flags);
> +	write_seqcount_begin(&syncp->seq);
> +#endif
> +	return flags;
> +}
> +
> +static inline void
> +u64_stats_update_end_irqrestore(struct u64_stats_sync *syncp,
> +				unsigned long flags)
> +{
> +#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
> +	write_seqcount_end(&syncp->seq);
> +	local_irq_restore(flags);
> +#endif
> +}
> +
>   static inline void u64_stats_update_begin_raw(struct u64_stats_sync *syncp)
>   {
>   #if BITS_PER_LONG==32 && defined(CONFIG_SMP)
>
>
>
>

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

Re: inconsistent lock state with usbnet/asix usb ethernet and xhci

[Eric Dumazet]

On Tue, 2018-02-27 at 15:42 +0100, Marek Szyprowski wrote:
> Hi Eric,
> 
> On 2018-02-27 15:07, Eric Dumazet wrote:
> > On Tue, 2018-02-27 at 08:26 +0100, Marek Szyprowski wrote:
> > > I've noticed that USBnet/ASIX AX88772B USB driver produces deplock kernel
> > > warning ("inconsistent lock state") on Chromebook2 Peach-PIT board. No
> > > special activity is needed to reproduce this issue, it happens almost
> > > on every boot. ASIX USB ethernet is connected to XHCI USB host controller
> > > on that board. Is it a known issue? Frankly I have no idea where to look
> > > to fix it. The same adapter connected to EHCI ports on other boards based
> > > on the same SoC works fine without any warnings.
> > > 
> > > Here are some more information from that board:
> > > # lsusb
> > > Bus 006 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
> > > Bus 005 Device 002: ID 0b95:772b ASIX Electronics Corp. AX88772B
> > > Bus 005 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
> > > Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
> > > Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
> > > Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
> > > Bus 001 Device 002: ID 2232:1056 Silicon Motion
> > > Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
> > > 
> > > # lsusb -t
> > > /:  Bus 06.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 5000M
> > > /:  Bus 05.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 480M
> > >       |__ Port 1: Dev 2, If 0, Class=Vendor Specific Class, Driver=asix, 480M
> > > /:  Bus 04.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 5000M
> > > /:  Bus 03.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 480M
> > > /:  Bus 02.Port 1: Dev 1, Class=root_hub, Driver=exynos-ohci/3p, 12M
> > > /:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=exynos-ehci/3p, 480M
> > >       |__ Port 1: Dev 2, If 0, Class=Video, Driver=, 480M
> > >       |__ Port 1: Dev 2, If 1, Class=Video, Driver=, 480M
> > > 
> > > 
> > > And the log with mentioned warning:
> > > 
> > > [   17.768040] ================================
> > > [   17.772239] WARNING: inconsistent lock state
> > > [   17.776511] 4.16.0-rc3-next-20180227-00007-g876c53a7493c #453 Not tainted
> > > [   17.783329] --------------------------------
> > > [   17.787580] inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
> > > [   17.793607] swapper/0/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
> > > [   17.798751]  (&syncp->seq#5){?.-.}, at: [<9b22e5f0>]
> > > asix_rx_fixup_internal+0x188/0x288
> > > [   17.806790] {IN-HARDIRQ-W} state was registered at:
> > > [   17.811677]   tx_complete+0x100/0x208
> > > [   17.815319]   __usb_hcd_giveback_urb+0x60/0xf0
> > > [   17.819770]   xhci_giveback_urb_in_irq+0xa8/0x240
> > > [   17.824469]   xhci_td_cleanup+0xf4/0x16c
> > > [   17.828367]   xhci_irq+0xe74/0x2240
> > > [   17.831827]   usb_hcd_irq+0x24/0x38
> > > [   17.835343]   __handle_irq_event_percpu+0x98/0x510
> > > [   17.840111]   handle_irq_event_percpu+0x1c/0x58
> > > [   17.844623]   handle_irq_event+0x38/0x5c
> > > [   17.848519]   handle_fasteoi_irq+0xa4/0x138
> > > [   17.852681]   generic_handle_irq+0x18/0x28
> > > [   17.856760]   __handle_domain_irq+0x6c/0xe4
> > > [   17.860941]   gic_handle_irq+0x54/0xa0
> > > [   17.864666]   __irq_svc+0x70/0xb0
> > > [   17.867964]   arch_cpu_idle+0x20/0x3c
> > > [   17.871578]   arch_cpu_idle+0x20/0x3c
> > > [   17.875190]   do_idle+0x144/0x218
> > > [   17.878468]   cpu_startup_entry+0x18/0x1c
> > > [   17.882454]   start_kernel+0x394/0x400
> > > [   17.886177] irq event stamp: 161912
> > > [   17.889616] hardirqs last  enabled at (161912): [<7bedfacf>]
> > > __netdev_alloc_skb+0xcc/0x140
> > > [   17.897893] hardirqs last disabled at (161911): [<d58261d0>]
> > > __netdev_alloc_skb+0x94/0x140
> > > [   17.904903] exynos5-hsi2c 12ca0000.i2c: tx timeout
> > > [   17.906116] softirqs last  enabled at (161904): [<387102ff>]
> > > irq_enter+0x78/0x80
> > > [   17.906123] softirqs last disabled at (161905): [<cf4c628e>]
> > > irq_exit+0x134/0x158
> > > [   17.925722].
> > > [   17.925722] other info that might help us debug this:
> > > [   17.933435]  Possible unsafe locking scenario:
> > > [   17.933435].
> > > [   17.940331]        CPU0
> > > [   17.942488]        ----
> > > [   17.944894]   lock(&syncp->seq#5);
> > > [   17.948274]   <Interrupt>
> > > [   17.950847]     lock(&syncp->seq#5);
> > > [   17.954386].
> > > [   17.954386]  *** DEADLOCK ***
> > > [   17.954386].
> > > [   17.962422] no locks held by swapper/0/0.
> > > [   17.966011].
> > > [   17.966011] stack backtrace:
> > > [   17.971333] CPU: 0 PID: 0 Comm: swapper/0 Not tainted
> > > 4.16.0-rc3-next-20180227-00007-g876c53a7493c #453
> > > [   17.980312] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
> > > [   17.986380] [<c0111548>] (unwind_backtrace) from [<c010dbd8>]
> > > (show_stack+0x10/0x14)
> > > [   17.994128] [<c010dbd8>] (show_stack) from [<c09bd418>]
> > > (dump_stack+0x90/0xc8)
> > > [   18.001339] [<c09bd418>] (dump_stack) from [<c017fdf8>]
> > > (print_usage_bug+0x25c/0x2cc)
> > > [   18.009161] [<c017fdf8>] (print_usage_bug) from [<c017c14c>]
> > > (mark_lock+0x290/0x698)
> > > [   18.014952] exynos5-hsi2c 12ca0000.i2c: tx timeout
> > > [   18.016899] [<c017c14c>] (mark_lock) from [<c017c9a8>]
> > > (__lock_acquire+0x454/0x1850)
> > > [   18.029449] [<c017c9a8>] (__lock_acquire) from [<c017e6e0>]
> > > (lock_acquire+0xc8/0x2b8)
> > > [   18.037272] [<c017e6e0>] (lock_acquire) from [<c05be98c>]
> > > (usbnet_skb_return+0x7c/0x1a0)
> > > [   18.045356] [<c05be98c>] (usbnet_skb_return) from [<c05b185c>]
> > > (asix_rx_fixup_internal+0x188/0x288)
> > > [   18.054420] [<c05b185c>] (asix_rx_fixup_internal) from [<c05bfe40>]
> > > (usbnet_bh+0xf8/0x2e4)
> > > [   18.062694] [<c05bfe40>] (usbnet_bh) from [<c012d6b4>]
> > > (tasklet_action+0x8c/0x13c)
> > > [   18.070259] [<c012d6b4>] (tasklet_action) from [<c0102214>]
> > > (__do_softirq+0xd4/0x6d4)
> > > [   18.078089] [<c0102214>] (__do_softirq) from [<c012cf34>]
> > > (irq_exit+0x134/0x158)
> > > [   18.085480] [<c012cf34>] (irq_exit) from [<c018c444>]
> > > (__handle_domain_irq+0x70/0xe4)
> > > [   18.093314] [<c018c444>] (__handle_domain_irq) from [<c046400c>]
> > > (gic_handle_irq+0x54/0xa0)
> > > [   18.101670] [<c046400c>] (gic_handle_irq) from [<c01019f0>]
> > > (__irq_svc+0x70/0xb0)
> > > [   18.109163] Exception stack(0xc0f01eb8 to 0xc0f01f00)
> > > [   18.114202] 1ea0: 00000001 00000001
> > > [   18.122397] 1ec0: 00000000 c0f0ba80 eef3a540 eef3a540 ee8d2700
> > > c0f088b4 00000402 c09d23e0
> > > [   18.124980] exynos5-hsi2c 12ca0000.i2c: tx timeout
> > > [   18.130611] 1ee0: c0f0ba80 c0f01f4c 00000000 c0f01f08 c017ea54
> > > c09d92d4 20000013 ffffffff
> > > [   18.135504] cpu cpu0: _set_opp_voltage: failed to set voltage
> > > (1250000 1250000 1250000 mV): -110
> > > [   18.143690] [<c01019f0>] (__irq_svc) from [<c09d92d4>]
> > > (_raw_spin_unlock_irq+0x28/0x5c)
> > > [   18.152671] cpufreq: __target_index: Failed to change cpu frequency: -110
> > > [   18.160683] [<c09d92d4>] (_raw_spin_unlock_irq) from [<c0152684>]
> > > (finish_task_switch+0xb4/0x254)
> > > [   18.160696] [<c0152684>] (finish_task_switch) from [<c09d23e0>]
> > > (__schedule+0x290/0xb10)
> > > [   18.160704] [<c09d23e0>] (__schedule) from [<c09d3134>]
> > > (schedule_idle+0x2c/0x78)
> > > [   18.160711] [<c09d3134>] (schedule_idle) from [<c01703a0>]
> > > (cpu_startup_entry+0x18/0x1c)
> > > [   18.200726] [<c01703a0>] (cpu_startup_entry) from [<c0e00c74>]
> > > (start_kernel+0x394/0x400)
> > > 
> > > Best regards
> > 
> > Please try the attached patch, thanks.
> 
> Thanks for the patch. It fixes the deplock warning. However IMHO the same
> fix should be also applied to complete_tx function for modifying stats64
> there:
> 
> diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
> index 7f5bda0ec9e8..d9eea8cfe6cb 100644
> --- a/drivers/net/usb/usbnet.c
> +++ b/drivers/net/usb/usbnet.c
> @@ -1249,11 +1249,12 @@ static void tx_complete (struct urb *urb)
> 
>          if (urb->status == 0) {
>                  struct pcpu_sw_netstats *stats64 = 
> this_cpu_ptr(dev->stats64);
> +               unsigned long flags;
> 
> -               u64_stats_update_begin(&stats64->syncp);
> +               flags = u64_stats_update_begin_irqsave(&stats64->syncp);
>                  stats64->tx_packets += entry->packets;
>                  stats64->tx_bytes += entry->length;
> -               u64_stats_update_end(&stats64->syncp);
> + u64_stats_update_end_irqrestore(&stats64->syncp, flags);
>          } else {
>                  dev->net->stats.tx_errors++;
> 
> 
> I've did that and it also works fine without deplock warning.

Note that for this one, it seems we also could perform stats updates in
BH context, since skb is queued via defer_bh()

But simplicity wins I guess.

I'll send a formal patch including your change in tx_complete(),
thanks !

Re: inconsistent lock state with usbnet/asix usb ethernet and xhci

[Eric Dumazet]

On Tue, 2018-02-27 at 07:09 -0800, Eric Dumazet wrote:
> 
> Note that for this one, it seems we also could perform stats updates in
> BH context, since skb is queued via defer_bh()
> 
> But simplicity wins I guess.

Thinking more about this, I am not sure we have any guarantee that TX
and RX can not run on multiple cpus.

Using an unique syncp is not going to be safe, even if we make lockdep
happy enough with the local_irq save/restore.

Re: inconsistent lock state with usbnet/asix usb ethernet and xhci

[Oliver Neukum]

Am Dienstag, den 27.02.2018, 07:13 -0800 schrieb Eric Dumazet:
> On Tue, 2018-02-27 at 07:09 -0800, Eric Dumazet wrote:
> > 
> > 
> > Note that for this one, it seems we also could perform stats updates in
> > BH context, since skb is queued via defer_bh()
> > 
> > But simplicity wins I guess.
> 
> Thinking more about this, I am not sure we have any guarantee that TX
> and RX can not run on multiple cpus.
> 
> Using an unique syncp is not going to be safe, even if we make lockdep
> happy enough with the local_irq save/restore.

Unfortunately you are right. It is not guaranteed for some hardware.

	Regards
		Oliver

Re: inconsistent lock state with usbnet/asix usb ethernet and xhci

[Marek Szyprowski]

Hi Oliver,

On 2018-02-27 17:07, Oliver Neukum wrote:
> Am Dienstag, den 27.02.2018, 07:13 -0800 schrieb Eric Dumazet:
>> On Tue, 2018-02-27 at 07:09 -0800, Eric Dumazet wrote:
>>>
>>> Note that for this one, it seems we also could perform stats updates in
>>> BH context, since skb is queued via defer_bh()
>>>
>>> But simplicity wins I guess.
>> Thinking more about this, I am not sure we have any guarantee that TX
>> and RX can not run on multiple cpus.
>>
>> Using an unique syncp is not going to be safe, even if we make lockdep
>> happy enough with the local_irq save/restore.
> Unfortunately you are right. It is not guaranteed for some hardware.

Does it mean that the fix proposed by Eric is not the proper solution?

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

Re: inconsistent lock state with usbnet/asix usb ethernet and xhci

[Oliver Neukum]

On Mon, 2018-03-05 at 08:45 +0100, Marek Szyprowski wrote:
> Hi Oliver,
> 
> On 2018-02-27 17:07, Oliver Neukum wrote:
> > Am Dienstag, den 27.02.2018, 07:13 -0800 schrieb Eric Dumazet:
> >> On Tue, 2018-02-27 at 07:09 -0800, Eric Dumazet wrote:
> >>>
> >>> Note that for this one, it seems we also could perform stats updates in
> >>> BH context, since skb is queued via defer_bh()
> >>>
> >>> But simplicity wins I guess.
> >> Thinking more about this, I am not sure we have any guarantee that TX
> >> and RX can not run on multiple cpus.
> >>
> >> Using an unique syncp is not going to be safe, even if we make lockdep
> >> happy enough with the local_irq save/restore.
> > Unfortunately you are right. It is not guaranteed for some hardware.
> 
> Does it mean that the fix proposed by Eric is not the proper solution?

For asix it should work, but asix is unlikely to be the only driver
with that issue. 32 bit recieves less testing nowadays.

	Regards
		Oliver

Re: inconsistent lock state with usbnet/asix usb ethernet and xhci

[Eric Dumazet]

On Mon, 2018-03-05 at 12:46 +0100, Oliver Neukum wrote:
> On Mon, 2018-03-05 at 08:45 +0100, Marek Szyprowski wrote:
> > Hi Oliver,
> > 
> > On 2018-02-27 17:07, Oliver Neukum wrote:
> > > Am Dienstag, den 27.02.2018, 07:13 -0800 schrieb Eric Dumazet:
> > > > On Tue, 2018-02-27 at 07:09 -0800, Eric Dumazet wrote:
> > > > > 
> > > > > Note that for this one, it seems we also could perform stats
> > > > > updates in
> > > > > BH context, since skb is queued via defer_bh()
> > > > > 
> > > > > But simplicity wins I guess.
> > > > 
> > > > Thinking more about this, I am not sure we have any guarantee
> > > > that TX
> > > > and RX can not run on multiple cpus.
> > > > 
> > > > Using an unique syncp is not going to be safe, even if we make
> > > > lockdep
> > > > happy enough with the local_irq save/restore.
> > > 
> > > Unfortunately you are right. It is not guaranteed for some
> > > hardware.
> > 
> > Does it mean that the fix proposed by Eric is not the proper
> > solution?
> 
> For asix it should work, but asix is unlikely to be the only driver
> with that issue. 32 bit recieves less testing nowadays.

Yes, although the lockdep part could be enforced in 64bit if we really
care.

I will send a patch using two different sync (one for RX, one for TX)

[PATCH net] net: usbnet: fix potential deadlock on 32bit hosts

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

Marek reported a LOCKDEP issue occurring on 32bit host,
that we tracked down to the fact that usbnet could either
run from soft or hard irqs.

This patch adds u64_stats_update_begin_irqsave() and
u64_stats_update_end_irqrestore() helpers to solve this case.

[   17.768040] ================================
[   17.772239] WARNING: inconsistent lock state
[   17.776511] 4.16.0-rc3-next-20180227-00007-g876c53a7493c #453 Not tainted
[   17.783329] --------------------------------
[   17.787580] inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
[   17.793607] swapper/0/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
[   17.798751]  (&syncp->seq#5){?.-.}, at: [<9b22e5f0>] 
asix_rx_fixup_internal+0x188/0x288
[   17.806790] {IN-HARDIRQ-W} state was registered at:
[   17.811677]   tx_complete+0x100/0x208
[   17.815319]   __usb_hcd_giveback_urb+0x60/0xf0
[   17.819770]   xhci_giveback_urb_in_irq+0xa8/0x240
[   17.824469]   xhci_td_cleanup+0xf4/0x16c
[   17.828367]   xhci_irq+0xe74/0x2240
[   17.831827]   usb_hcd_irq+0x24/0x38
[   17.835343]   __handle_irq_event_percpu+0x98/0x510
[   17.840111]   handle_irq_event_percpu+0x1c/0x58
[   17.844623]   handle_irq_event+0x38/0x5c
[   17.848519]   handle_fasteoi_irq+0xa4/0x138
[   17.852681]   generic_handle_irq+0x18/0x28
[   17.856760]   __handle_domain_irq+0x6c/0xe4
[   17.860941]   gic_handle_irq+0x54/0xa0
[   17.864666]   __irq_svc+0x70/0xb0
[   17.867964]   arch_cpu_idle+0x20/0x3c
[   17.871578]   arch_cpu_idle+0x20/0x3c
[   17.875190]   do_idle+0x144/0x218
[   17.878468]   cpu_startup_entry+0x18/0x1c
[   17.882454]   start_kernel+0x394/0x400
[   17.886177] irq event stamp: 161912
[   17.889616] hardirqs last  enabled at (161912): [<7bedfacf>] 
__netdev_alloc_skb+0xcc/0x140
[   17.897893] hardirqs last disabled at (161911): [<d58261d0>] 
__netdev_alloc_skb+0x94/0x140
[   17.904903] exynos5-hsi2c 12ca0000.i2c: tx timeout
[   17.906116] softirqs last  enabled at (161904): [<387102ff>] 
irq_enter+0x78/0x80
[   17.906123] softirqs last disabled at (161905): [<cf4c628e>] 
irq_exit+0x134/0x158
[   17.925722].
[   17.925722] other info that might help us debug this:
[   17.933435]  Possible unsafe locking scenario:
[   17.933435].
[   17.940331]        CPU0
[   17.942488]        ----
[   17.944894]   lock(&syncp->seq#5);
[   17.948274]   <Interrupt>
[   17.950847]     lock(&syncp->seq#5);
[   17.954386].
[   17.954386]  *** DEADLOCK ***
[   17.954386].
[   17.962422] no locks held by swapper/0/0.

Fixes: c8b5d129ee29 ("net: usbnet: support 64bit stats")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Greg Ungerer <gerg@linux-m68k.org>
---
 drivers/net/usb/usbnet.c       |   10 ++++++----
 include/linux/u64_stats_sync.h |   22 ++++++++++++++++++++++
 2 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index 8a22ff67b0268a588428c61c6a6211e3c6c2a02a..d9eea8cfe6cb9a3bf8d0d4ce9198af9bccf9c757 100644
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -315,6 +315,7 @@ static void __usbnet_status_stop_force(struct usbnet *dev)
 void usbnet_skb_return (struct usbnet *dev, struct sk_buff *skb)
 {
 	struct pcpu_sw_netstats *stats64 = this_cpu_ptr(dev->stats64);
+	unsigned long flags;
 	int	status;
 
 	if (test_bit(EVENT_RX_PAUSED, &dev->flags)) {
@@ -326,10 +327,10 @@ void usbnet_skb_return (struct usbnet *dev, struct sk_buff *skb)
 	if (skb->protocol == 0)
 		skb->protocol = eth_type_trans (skb, dev->net);
 
-	u64_stats_update_begin(&stats64->syncp);
+	flags = u64_stats_update_begin_irqsave(&stats64->syncp);
 	stats64->rx_packets++;
 	stats64->rx_bytes += skb->len;
-	u64_stats_update_end(&stats64->syncp);
+	u64_stats_update_end_irqrestore(&stats64->syncp, flags);
 
 	netif_dbg(dev, rx_status, dev->net, "< rx, len %zu, type 0x%x\n",
 		  skb->len + sizeof (struct ethhdr), skb->protocol);
@@ -1248,11 +1249,12 @@ static void tx_complete (struct urb *urb)
 
 	if (urb->status == 0) {
 		struct pcpu_sw_netstats *stats64 = this_cpu_ptr(dev->stats64);
+		unsigned long flags;
 
-		u64_stats_update_begin(&stats64->syncp);
+		flags = u64_stats_update_begin_irqsave(&stats64->syncp);
 		stats64->tx_packets += entry->packets;
 		stats64->tx_bytes += entry->length;
-		u64_stats_update_end(&stats64->syncp);
+		u64_stats_update_end_irqrestore(&stats64->syncp, flags);
 	} else {
 		dev->net->stats.tx_errors++;
 
diff --git a/include/linux/u64_stats_sync.h b/include/linux/u64_stats_sync.h
index 5bdbd9f49395f883ca2dc5aa0d7bbde11f379063..07ee0f84a46caa9e2b1c446f96009f63b3b99f50 100644
--- a/include/linux/u64_stats_sync.h
+++ b/include/linux/u64_stats_sync.h
@@ -90,6 +90,28 @@ static inline void u64_stats_update_end(struct u64_stats_sync *syncp)
 #endif
 }
 
+static inline unsigned long
+u64_stats_update_begin_irqsave(struct u64_stats_sync *syncp)
+{
+	unsigned long flags = 0;
+
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
+	local_irq_save(flags);
+	write_seqcount_begin(&syncp->seq);
+#endif
+	return flags;
+}
+
+static inline void
+u64_stats_update_end_irqrestore(struct u64_stats_sync *syncp,
+				unsigned long flags)
+{
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
+	write_seqcount_end(&syncp->seq);
+	local_irq_restore(flags);
+#endif
+}
+
 static inline void u64_stats_update_begin_raw(struct u64_stats_sync *syncp)
 {
 #if BITS_PER_LONG==32 && defined(CONFIG_SMP)

Re: [PATCH net] net: usbnet: fix potential deadlock on 32bit hosts

[David Miller]

From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Mon, 05 Mar 2018 11:41:13 -0800

> From: Eric Dumazet <edumazet@google.com>
> 
> Marek reported a LOCKDEP issue occurring on 32bit host,
> that we tracked down to the fact that usbnet could either
> run from soft or hard irqs.
> 
> This patch adds u64_stats_update_begin_irqsave() and
> u64_stats_update_end_irqrestore() helpers to solve this case.
 ...
> Fixes: c8b5d129ee29 ("net: usbnet: support 64bit stats")
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
> Cc: Greg Ungerer <gerg@linux-m68k.org>

Applied and queued up for -stable, thanks Eric.