I have been using higher MTU for performance reasons successfully with earlier L4T releases, for example with 32.4.4. However in L4T 32.5.1 the kernel panics quite soon after MTU is increased. Is this a known problem/is there a fix or workaround available?
Most of the time it’s something related to SKB (some buffer size mismatches as MTU is increased?). Example session:
sudo ifconfig eth0 mtu 5000 dmesg|tail
[ 31.814700] vdd-3v3: disabling
[ 31.814711] en-vdd-vcm-2v8: disabling
[ 31.814722] vdd-sys-bl: disabling
[ 31.814731] en-vdd-sys: disabling
[ 48.754054] eqos 2490000.ether_qos: changing MTU from 1500 to 5000
[ 48.754389] bcm54xx_low_power_mode(): put phy in iddq-lp mode
[ 48.836876] gpio tegra-gpio wake18 for gpio=101(M:5)
[ 52.308129] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
[ 52.375521] eqos 2490000.ether_qos eth0: Link is Up - 1Gbps/Full - flow control off
[ 52.376847] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
In this case it crashes only four seconds after link is back up:
[ 56.782076] kernel BUG at /dvs/git/dirty/git-master_linux/kernel/kernel-4.9/mm/slub.c:3873!
[ 56.790680] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
[ 56.796320] Modules linked in: zram 8021q garp mrp spidev ov5693 overlay userspace_alert nvgpu bluedroid_pm ip_tables x_tables
[ 56.808394] CPU: 0 PID: 3 Comm: ksoftirqd/0 Not tainted 4.9.201-tegra #1
[ 56.815269] Hardware name: lightning (DT)
[ 56.819397] task: ffffffc0f0f11c00 task.stack: ffffffc0f0f34000
[ 56.825487] PC is at kfree+0x254/0x2a8
[ 56.829351] LR is at skb_free_head+0x28/0x48
[ 56.833741] pc : [] lr : [] pstate: 40400045
[ 56.841324] sp : ffffffc0f0f377b0
[ 56.844734] x29: ffffffc0f0f377b0 x28: ffffffc0ef3ea900
[ 56.850246] x27: ffffffc0e59a9700 x26: 0000000000000000
[ 56.855756] x25: ffffff800a077100 x24: ffffffc0c1fcc064
[ 56.861262] x23: ffffffc0d0f89a28 x22: ffffffc0c1fcc000
[ 56.866767] x21: ffffffc0d0f89a00 x20: ffffff8008d96710
[ 56.872271] x19: ffffffbf0307f300 x18: 000000000000088e
[ 56.877776] x17: 0000000000000000 x16: 0000000000000000
[ 56.883281] x15: 000000000003d20a x14: 0000000000000001
[ 56.888784] x13: 0000000000000000 x12: 0000000000000008
[ 56.894286] x11: ffffff800917c030 x10: 0000000000000008
[ 56.899793] x9 : 0000000000000000 x8 : 00000000000000c8
[ 56.905299] x7 : 0000000000000001 x6 : ffffffc0d7d6ec80
[ 56.910806] x5 : ffffffc0f0f11c00 x4 : ffffffc0f5f80140
[ 56.916313] x3 : ffffffc0c1fcc000 x2 : 0000000000001ec0
[ 56.921816] x1 : 0000000000000000 x0 : 0000000000000000
[ 56.927319]
[ 56.928868] Process ksoftirqd/0 (pid: 3, stack limit = 0xffffffc0f0f34000)
[ 56.935919] Call trace:
[ 56.938453] [] kfree+0x254/0x2a8
[ 56.943379] [] skb_free_head+0x28/0x48
[ 56.948837] [] skb_release_data+0x100/0x130
[ 56.954736] [] skb_release_all+0x30/0x40
[ 56.960369] [] kfree_skb+0x40/0x120
[ 56.965560] [] __udp4_lib_rcv+0x6a8/0xaa8
[ 56.971282] [] udp_rcv+0x30/0x40
[ 56.976207] [] ip_local_deliver_finish+0x80/0x280
[ 56.982639] [] ip_local_deliver+0x54/0xf0
[ 56.988360] [] ip_rcv_finish+0x1f8/0x380
[ 56.993992] [] ip_rcv+0x284/0x390
[ 56.999007] [] __netif_receive_skb_core+0x3b8/0xad8
[ 57.005620] [] __netif_receive_skb+0x28/0x78
[ 57.011612] [] netif_receive_skb_internal+0x2c/0xb0
[ 57.018226] [] napi_gro_receive+0x15c/0x188
[ 57.024131] [] eqos_napi_poll_rx+0x368/0x4f8
[ 57.030120] [] net_rx_action+0xf4/0x358
[ 57.035666] [] __do_softirq+0x13c/0x3b0
[ 57.041215] [] run_ksoftirqd+0x48/0x58
[ 57.046676] [] smpboot_thread_fn+0x160/0x248
[ 57.052663] [] kthread+0xec/0xf0
[ 57.065283] [] ret_from_fork+0x10/0x30
[ 57.078292] —[ end trace c485d8a89eef9e66 ]—
[ 57.120358] Kernel panic - not syncing: Fatal exception in interrupt
[ 57.134340] SMP: stopping secondary CPUs
[ 57.145782] Kernel Offset: disabled
[ 57.156661] Memory Limit: none
[ 57.167064] trusty-log panic notifier - trusty version Built: 19:52:41 Mar 2 2021 [ 57.204251] Rebooting in 5 seconds…