> -----Original Message-----
> From: Souradeep Chakrabarti <[email protected]>
> Sent: Tuesday, January 30, 2024 5:16 AM
> To: KY Srinivasan <[email protected]>; Haiyang Zhang
> <[email protected]>; [email protected]; Dexuan Cui
> <[email protected]>; [email protected]; [email protected];
> [email protected]; [email protected]; Long Li <[email protected]>;
> [email protected]; [email protected]; [email protected];
> [email protected]; [email protected]; [email protected];
> [email protected]; [email protected]; linux-
> [email protected]; [email protected]
> Cc: Souradeep Chakrabarti <[email protected]>; Souradeep
> Chakrabarti <[email protected]>
> Subject: [PATCH net] hv_netvsc: Fix race condition between netvsc_probe
> and netvsc_remove
>
> In commit ac5047671758 ("hv_netvsc: Disable NAPI before closing the
> VMBus channel"), napi_disable was getting called for all channels,
> including all subchannels without confirming if they are enabled or not.
>
> Which caused hv_netvsc getting hung at napi_disable, when netvsc_probe()
> and netvsc_remove() are happening simultaneously and netvsc_remove()
> calls cancel_work_sync(&nvdev->subchan_work) before netvsc_sc_open()
> calls napi_enable for the sub channels. Which causes NAPIF_STATE_SCHED
> bit not getting cleared for the subchannels.
>
> Now during netvsc_device_remove(), when napi_disable is called for those
> subchannels, napi_disable gets stuck on infinite msleep.
>
> Call trace:
> [ 654.559417] task:modprobe state:D stack: 0 pid: 2321 ppid:
> 1091 flags:0x00004002
> [ 654.568030] Call Trace:
> [ 654.571221] <TASK>
> [ 654.573790] __schedule+0x2d6/0x960
> [ 654.577733] schedule+0x69/0xf0
> [ 654.581214] schedule_timeout+0x87/0x140
> [ 654.585463] ? __bpf_trace_tick_stop+0x20/0x20
> [ 654.590291] msleep+0x2d/0x40
> [ 654.593625] napi_disable+0x2b/0x80
> [ 654.597437] netvsc_device_remove+0x8a/0x1f0 [hv_netvsc]
> [ 654.603935] rndis_filter_device_remove+0x194/0x1c0 [hv_netvsc]
> [ 654.611101] ? do_wait_intr+0xb0/0xb0
> [ 654.615753] netvsc_remove+0x7c/0x120 [hv_netvsc]
> [ 654.621675] vmbus_remove+0x27/0x40 [hv_vmbus]
>
> Fixes: ac5047671758 ("hv_netvsc: Disable NAPI before closing the VMBus
> channel")
> Signed-off-by: Souradeep Chakrabarti <[email protected]>
Please add:
Cc: [email protected]
Otherwise, all look good!
Reviewed-by: Haiyang Zhang <[email protected]>
> ---
> drivers/net/hyperv/netvsc.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
> index 1dafa44155d0..a6fcbda64ecc 100644
> --- a/drivers/net/hyperv/netvsc.c
> +++ b/drivers/net/hyperv/netvsc.c
> @@ -708,7 +708,10 @@ void netvsc_device_remove(struct hv_device *device)
> /* Disable NAPI and disassociate its context from the device. */
> for (i = 0; i < net_device->num_chn; i++) {
> /* See also vmbus_reset_channel_cb(). */
> - napi_disable(&net_device->chan_table[i].napi);
> + /* only disable enabled NAPI channel */
> + if (i < ndev->real_num_rx_queues)
> + napi_disable(&net_device->chan_table[i].napi);
> +
> netif_napi_del(&net_device->chan_table[i].napi);
> }
>
> --
> 2.34.1
