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Date: Tue, 10 Jan 2017 15:36:47 +0100
From: Mason <slash.tmp@...e.fr>
To: netdev <netdev@...r.kernel.org>
Cc: Mans Rullgard <mans@...sr.com>,
Thibaud Cornic <thibaud_cornic@...madesigns.com>,
Thomas Gambier <thomas_gambier@...madesigns.com>
Subject: Setting link down hangs the kernel
Hello,
I'm using kernel v4.9 on a dev board.
I built a small kernel + rootfs with buildroot 2016.11.1
eth0 is driven by drivers/net/ethernet/aurora/nb8800.c
After booting, I just run udhcpc (busybox version)
Then I set the link down, and the kernel hangs.
Here's the console output:
[ 1.116707] Freeing unused kernel memory: 3072K (c0600000 - c0900000)
Starting logging: OK
Initializing random number generator... [ 1.217335] random: dd: uninitialized urandom read (512 bytes read)
done.
Starting network: OK
Welcome to Buildroot
buildroot login: root
# udhcpc
udhcpc: started, v1.25.1
udhcpc: sending discover
udhcpc: sending discover
[ 13.840512] nb8800 26000.ethernet eth0: Link is Up - 1Gbps/Full - flow control rx/tx
udhcpc: sending discover
udhcpc: sending select for 172.27.64.51
udhcpc: lease of 172.27.64.51 obtained, lease time 604800
deleting routers
adding dns 172.27.0.17
# ip link set dev eth0 down
[ 65.520187] nb8800 26000.ethernet eth0: Link is Down
^C^C^C
[ 85.790557] sysrq: SysRq : Show backtrace of all active CPUs
[ 85.796260] NMI backtrace for cpu 0
[ 85.799773] CPU: 0 PID: 866 Comm: ip Not tainted 4.9.0 #143
[ 85.805376] Hardware name: Sigma Tango DT
[ 85.809405] Backtrace:
[ 85.811893] [<c010ad6c>] (dump_backtrace) from [<c010b00c>] (show_stack+0x18/0x1c)
[ 85.819510] r7:00000000 r6:600c0193 r5:00000000 r4:c0910af4
[ 85.825216] [<c010aff4>] (show_stack) from [<c029264c>] (dump_stack+0x84/0xa0)
[ 85.832491] [<c02925c8>] (dump_stack) from [<c0295c60>] (nmi_cpu_backtrace+0x98/0xb8)
[ 85.840370] r7:00000000 r6:c010c9e4 r5:00000000 r4:00000000
[ 85.846074] [<c0295bc8>] (nmi_cpu_backtrace) from [<c0295d44>] (nmi_trigger_cpumask_backtrace+0xc4/0x17c)
[ 85.855696] r5:00000000 r4:c09032e4
[ 85.859304] [<c0295c80>] (nmi_trigger_cpumask_backtrace) from [<c010d3a4>] (arch_trigger_cpumask_backtrace+0x14/0x1c)
[ 85.869981] r9:00000100 r8:00000001 r7:0000006c r6:0000000a r5:c090ac48 r4:c0911458
[ 85.877783] [<c010d390>] (arch_trigger_cpumask_backtrace) from [<c02caea4>] (sysrq_handle_showallcpus+0x18/0x20)
[ 85.888027] [<c02cae8c>] (sysrq_handle_showallcpus) from [<c02cb5c0>] (__handle_sysrq+0x90/0x12c)
[ 85.896958] [<c02cb530>] (__handle_sysrq) from [<c02cb684>] (handle_sysrq+0x28/0x2c)
[ 85.904751] r9:00000100 r8:00000000 r7:0000006c r6:00000061 r5:00000061 r4:0000006c
[ 85.912553] [<c02cb65c>] (handle_sysrq) from [<c02de4e4>] (serial8250_rx_chars+0x178/0x1d8)
[ 85.920952] r5:00000061 r4:c094e654
[ 85.924557] [<c02de36c>] (serial8250_rx_chars) from [<c02dfe40>] (serial8250_handle_irq+0x8c/0xdc)
[ 85.933575] r10:00000014 r9:cfbea6cc r8:cfbea6c0 r7:600c0193 r6:00000061 r5:000000cc
[ 85.941448] r4:c094e654
[ 85.944002] [<c02dfdb4>] (serial8250_handle_irq) from [<c02dff28>] (serial8250_default_handle_irq+0x30/0x44)
[ 85.953888] r7:00000000 r6:00000000 r5:00000000 r4:c094e654
[ 85.959588] [<c02dfef8>] (serial8250_default_handle_irq) from [<c02dce6c>] (serial8250_interrupt+0x3c/0xbc)
[ 85.969383] r5:00000000 r4:c094e768
[ 85.972993] [<c02dce30>] (serial8250_interrupt) from [<c01582e8>] (__handle_irq_event_percpu+0x40/0x10c)
[ 85.982534] r10:c090c7b5 r9:cfa57c54 r8:cf866a00 r7:00000001 r6:00000014 r5:00000000
[ 85.990409] r4:cfbea680 r3:c02dce30
[ 85.994015] [<c01582a8>] (__handle_irq_event_percpu) from [<c01583d8>] (handle_irq_event_percpu+0x24/0x60)
[ 86.003730] r10:ffffffff r9:cfa56000 r8:00000002 r7:00000001 r6:cf866a10 r5:cf866a00
[ 86.011602] r4:cf866a00
[ 86.014159] [<c01583b4>] (handle_irq_event_percpu) from [<c0158454>] (handle_irq_event+0x40/0x64)
[ 86.023082] r5:cf866a60 r4:cf866a00
[ 86.026686] [<c0158414>] (handle_irq_event) from [<c015bc68>] (handle_level_irq+0xdc/0x118)
[ 86.035087] r7:00000001 r6:cf866a10 r5:cf866a60 r4:cf866a00
[ 86.040787] [<c015bb8c>] (handle_level_irq) from [<c015768c>] (generic_handle_irq+0x20/0x30)
[ 86.049275] r7:00000001 r6:00000000 r5:cf802600 r4:00000001
[ 86.054976] [<c015766c>] (generic_handle_irq) from [<c02b537c>] (tangox_dispatch_irqs+0x4c/0x58)
[ 86.063820] [<c02b5330>] (tangox_dispatch_irqs) from [<c02b5404>] (tangox_irq_handler+0x7c/0xa4)
[ 86.072662] r9:cfa56000 r8:cf802400 r7:00000000 r6:c0903310 r5:cf802600 r4:cf804010
[ 86.080458] [<c02b5388>] (tangox_irq_handler) from [<c015768c>] (generic_handle_irq+0x20/0x30)
[ 86.089121] r7:00000010 r6:c0866edc r5:00000000 r4:00000000
[ 86.094822] [<c015766c>] (generic_handle_irq) from [<c0157c14>] (__handle_domain_irq+0x94/0xbc)
[ 86.103578] [<c0157b80>] (__handle_domain_irq) from [<c010142c>] (gic_handle_irq+0x50/0x7c)
[ 86.111984] r9:cfa56000 r8:00000000 r7:f0701100 r6:cfa57d60 r5:c0903310 r4:f0700100
[ 86.119778] [<c01013dc>] (gic_handle_irq) from [<c010bb0c>] (__irq_svc+0x6c/0xa8)
[ 86.127303] Exception stack(0xcfa57d60 to 0xcfa57da8)
[ 86.132390] 7d60: cfb2f800 00000000 f0026000 00240aff cfb2f800 cfbe1400 00001042 00001003
[ 86.140621] 7d80: 00000000 00000000 ffffffff cfa57dbc cfa57dc0 cfa57db0 c0312e8c c0310ad4
[ 86.148843] 7da0: 200c0013 ffffffff
[ 86.152354] r7:cfa57d94 r6:ffffffff r5:200c0013 r4:c0310ad4
[ 86.158058] [<c0310ac8>] (nb8800_mac_tx) from [<c0312e8c>] (nb8800_stop+0x60/0x84)
[ 86.165683] [<c0312e2c>] (nb8800_stop) from [<c033e094>] (__dev_close_many+0x9c/0xc0)
[ 86.173558] r5:cfa57df0 r4:cfb2f800
[ 86.177160] [<c033dff8>] (__dev_close_many) from [<c033e1c8>] (__dev_close+0x30/0x48)
[ 86.185035] r5:00000001 r4:cfb2f800
[ 86.188639] [<c033e198>] (__dev_close) from [<c0345898>] (__dev_change_flags+0x94/0x138)
[ 86.196781] [<c0345804>] (__dev_change_flags) from [<c034595c>] (dev_change_flags+0x20/0x50)
[ 86.205273] r9:00000000 r8:00000000 r7:00000000 r6:cfb2f944 r5:00001003 r4:cfb2f800
[ 86.213072] [<c034593c>] (dev_change_flags) from [<c039e8f4>] (devinet_ioctl+0x308/0x67c)
[ 86.221303] r9:00000000 r8:cfa1c20c r7:00000000 r6:cfb2f800 r5:cfa1c200 r4:cfada500
[ 86.229098] [<c039e5ec>] (devinet_ioctl) from [<c03a09f8>] (inet_ioctl+0xc4/0xf8)
[ 86.236630] r10:00000000 r9:cfa56000 r8:be97dc80 r7:00008914 r6:be97dc80 r5:00008914
[ 86.244502] r4:c03a0934
[ 86.247062] [<c03a0934>] (inet_ioctl) from [<c032a9ec>] (sock_ioctl+0x24c/0x29c)
[ 86.254500] r5:00008914 r4:c03a0934
[ 86.258108] [<c032a7a0>] (sock_ioctl) from [<c01db9d0>] (vfs_ioctl+0x28/0x3c)
[ 86.265288] r7:00008914 r6:cfa61900 r5:cf43a0a0 r4:be97dc80
[ 86.270989] [<c01db9a8>] (vfs_ioctl) from [<c01dc270>] (do_vfs_ioctl+0x764/0x8b8)
[ 86.278523] [<c01dbb0c>] (do_vfs_ioctl) from [<c01dc400>] (SyS_ioctl+0x3c/0x64)
[ 86.285881] r10:00000000 r9:cfa56000 r8:be97dc80 r7:00008914 r6:cfa61900 r5:cfa61900
[ 86.293753] r4:00000003
[ 86.296309] [<c01dc3c4>] (SyS_ioctl) from [<c0107260>] (ret_fast_syscall+0x0/0x3c)
[ 86.303929] r9:cfa56000 r8:c0107424 r7:00000036 r6:00000003 r5:00000001 r4:000a15bb
^C^C^C^C^C
Looks like the kernel is wedged in nb8800_mac_tx.
static void nb8800_mac_tx(struct net_device *dev, bool enable)
{
struct nb8800_priv *priv = netdev_priv(dev);
while (nb8800_readl(priv, NB8800_TXC_CR) & TCR_EN)
cpu_relax();
nb8800_modb(priv, NB8800_TX_CTL1, TX_EN, enable);
}
c0310ac8 <nb8800_mac_tx>:
c0310ac8: e1a0c00d mov ip, sp
c0310acc: e92dd800 push {fp, ip, lr, pc}
c0310ad0: e24cb004 sub fp, ip, #4
c0310ad4: e5902530 ldr r2, [r0, #1328] ; 0x530
c0310ad8: e5923100 ldr r3, [r2, #256] ; 0x100
c0310adc: e3130001 tst r3, #1
c0310ae0: 0a000000 beq c0310ae8 <nb8800_mac_tx+0x20>
c0310ae4: eafffffa b c0310ad4 <nb8800_mac_tx+0xc>
c0310ae8: e5d23000 ldrb r3, [r2]
c0310aec: e6ef3073 uxtb r3, r3
c0310af0: e0211003 eor r1, r1, r3
c0310af4: e2011001 and r1, r1, #1
c0310af8: e0211003 eor r1, r1, r3
c0310afc: e1530001 cmp r3, r1
c0310b00: 089da800 ldmeq sp, {fp, sp, pc}
c0310b04: e5c21000 strb r1, [r2]
c0310b08: e89da800 ldm sp, {fp, sp, pc}
If I'm reading the exception stack correctly, the CPU was at c0310ad4,
i.e. it's stuck in the while loop.
Time for me to hit the data sheet, I guess :-(
While investigating this bug, I also hit a different symptom:
# ip link set dev eth0 down
# ip link set dev eth0 up
# [ 252.560722] nb8800 26000.ethernet eth0: Link is Down
[ 254.587431] nb8800 26000.ethernet eth0: Link is Up - 1Gbps/Full - flow control rx/tx
# ip link set dev eth0 down
[ 257.673295] nb8800 26000.ethernet eth0: RX Status FIFO overflow
[ 257.773613] nb8800 26000.ethernet eth0: RX Status FIFO overflow
[ 257.873807] nb8800 26000.ethernet eth0: RX Status FIFO overflow
[ 257.973981] nb8800 26000.ethernet eth0: RX Status FIFO overflow
[ 258.074160] nb8800 26000.ethernet eth0: RX Status FIFO overflow
# ip link set dev eth0 up
# [ 261.787381] nb8800 26000.ethernet eth0: Link is Down
[ 263.814093] nb8800 26000.ethernet eth0: Link is Up - 1Gbps/Full - flow control rx/tx
# ip link set dev eth0 down
[ 268.723656] nb8800 26000.ethernet eth0: RX Status FIFO overflow
[ 268.823980] nb8800 26000.ethernet eth0: RX Status FIFO overflow
[ 268.880451] nb8800 26000.ethernet eth0: Link is Down
^C^C^C^C
Regards.
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