Re: [PATCH net] net: stmmac: fix call trace when stmmac_xdp_xmit() is invoked

[Simon Horman]

On Wed, May 24, 2023 at 08:57:14PM +0800, wei.fang@xxxxxxx wrote:
> From: Wei Fang <wei.fang@xxxxxxx>
> 
> We encountered a kernel call trace issue which was related to
> ndo_xdp_xmit callback on our i.MX8MP platform. The reproduce
> steps show as follows.
> 1. The FEC port (eth0) connects to a PC port, and the PC uses
> pktgen_sample03_burst_single_flow.sh to generate packets and
> send these packets to the FEC port. Notice that the script must
> be executed before step 2.
> 2. Run the "./xdp_redirect eth0 eth1" command on i.MX8MP, the
> eth1 interface is the dwmac. Then there will be a call trace
> issue soon. Please see the log for more details.
> The root cause is that the NETDEV_XDP_ACT_NDO_XMIT feature is
> enabled by default, so when the step 2 command is exexcuted
> and packets have already been sent to eth0, the stmmac_xdp_xmit()
> starts running before the stmmac_xdp_set_prog() finishes. To
> resolve this issue, we disable the NETDEV_XDP_ACT_NDO_XMIT
> feature by default and turn on/off this feature when the bpf
> program is installed/uninstalled which just like the other
> ethernet drivers.
> 
> Call Trace log:
> [  306.311271] ------------[ cut here ]------------
> [  306.315910] WARNING: CPU: 0 PID: 15 at lib/timerqueue.c:55 timerqueue_del+0x68/0x70
> [  306.323590] Modules linked in:
> [  306.326654] CPU: 0 PID: 15 Comm: ksoftirqd/0 Not tainted 6.4.0-rc1+ #37
> [  306.333277] Hardware name: NXP i.MX8MPlus EVK board (DT)
> [  306.338591] pstate: 600000c5 (nZCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [  306.345561] pc : timerqueue_del+0x68/0x70
> [  306.349577] lr : __remove_hrtimer+0x5c/0xa0
> [  306.353777] sp : ffff80000b7c3920
> [  306.357094] x29: ffff80000b7c3920 x28: 0000000000000000 x27: 0000000000000001
> [  306.364244] x26: ffff80000a763a40 x25: ffff0000d0285a00 x24: 0000000000000001
> [  306.371390] x23: 0000000000000001 x22: ffff000179389a40 x21: 0000000000000000
> [  306.378537] x20: ffff000179389aa0 x19: ffff0000d2951308 x18: 0000000000001000
> [  306.385686] x17: f1d3000000000000 x16: 00000000c39c1000 x15: 55e99bbe00001a00
> [  306.392835] x14: 09000900120aa8c0 x13: e49af1d300000000 x12: 000000000000c39c
> [  306.399987] x11: 100055e99bbe0000 x10: ffff8000090b1048 x9 : ffff8000081603fc
> [  306.407133] x8 : 000000000000003c x7 : 000000000000003c x6 : 0000000000000001
> [  306.414284] x5 : ffff0000d2950980 x4 : 0000000000000000 x3 : 0000000000000000
> [  306.421432] x2 : 0000000000000001 x1 : ffff0000d2951308 x0 : ffff0000d2951308
> [  306.428585] Call trace:
> [  306.431035]  timerqueue_del+0x68/0x70
> [  306.434706]  __remove_hrtimer+0x5c/0xa0
> [  306.438549]  hrtimer_start_range_ns+0x2bc/0x370
> [  306.443089]  stmmac_xdp_xmit+0x174/0x1b0
> [  306.447021]  bq_xmit_all+0x194/0x4b0
> [  306.450612]  __dev_flush+0x4c/0x98
> [  306.454024]  xdp_do_flush+0x18/0x38
> [  306.457522]  fec_enet_rx_napi+0x6c8/0xc68
> [  306.461539]  __napi_poll+0x40/0x220
> [  306.465038]  net_rx_action+0xf8/0x240
> [  306.468707]  __do_softirq+0x128/0x3a8
> [  306.472378]  run_ksoftirqd+0x40/0x58
> [  306.475961]  smpboot_thread_fn+0x1c4/0x288
> [  306.480068]  kthread+0x124/0x138
> [  306.483305]  ret_from_fork+0x10/0x20
> [  306.486889] ---[ end trace 0000000000000000 ]---
> 
> Fixes: 66c0e13ad236 ("drivers: net: turn on XDP features")
> Signed-off-by: Wei Fang <wei.fang@xxxxxxx>

This looks good to me.

Reviewed-by: Simon Horman <simon.horman@xxxxxxxxxxxx>

Alexandre, is there any feedback from your side?