RE: [PATCH net] hv_netvsc: Fix race condition between netvsc_probe and netvsc_remove

[Haiyang Zhang]

> -----Original Message-----
> From: Souradeep Chakrabarti <schakrabarti@xxxxxxxxxxxxxxxxxxx>
> Sent: Tuesday, January 30, 2024 5:16 AM
> To: KY Srinivasan <kys@xxxxxxxxxxxxx>; Haiyang Zhang
> <haiyangz@xxxxxxxxxxxxx>; wei.liu@xxxxxxxxxx; Dexuan Cui
> <decui@xxxxxxxxxxxxx>; davem@xxxxxxxxxxxxx; edumazet@xxxxxxxxxx;
> kuba@xxxxxxxxxx; pabeni@xxxxxxxxxx; Long Li <longli@xxxxxxxxxxxxx>;
> yury.norov@xxxxxxxxx; leon@xxxxxxxxxx; cai.huoqing@xxxxxxxxx;
> ssengar@xxxxxxxxxxxxxxxxxxx; vkuznets@xxxxxxxxxx; tglx@xxxxxxxxxxxxx;
> linux-hyperv@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; linux-rdma@xxxxxxxxxxxxxxx
> Cc: Souradeep Chakrabarti <schakrabarti@xxxxxxxxxxxxx>; Souradeep
> Chakrabarti <schakrabarti@xxxxxxxxxxxxxxxxxxx>
> 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 <schakrabarti@xxxxxxxxxxxxxxxxxxx>

Please add:
Cc: stable@xxxxxxxxxxxxxxx

Otherwise, all look good!

Reviewed-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>

> ---
>  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