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.
This caused hv_netvsc getting hung at napi_disable, when netvsc_probe()
has finished running but nvdev->subchan_work has not started yet.
netvsc_subchan_work() -> rndis_set_subchannel() has not created the
sub-channels and because of that netvsc_sc_open() is not running.
netvsc_remove() calls cancel_work_sync(&nvdev->subchan_work), for which
netvsc_subchan_work did not run.
netif_napi_add() sets the bit NAPI_STATE_SCHED because it ensures NAPI
cannot be scheduled. Then netvsc_sc_open() -> napi_enable will clear the
NAPIF_STATE_SCHED bit, so it can be scheduled. napi_disable() does the
opposite.
Now during netvsc_device_remove(), when napi_disable is called for those
subchannels, napi_disable gets stuck on infinite msleep.
This fix addresses this problem by ensuring that napi_disable() is not
getting called for non-enabled NAPI struct.
But netif_napi_del() is still necessary for these non-enabled NAPI struct
for cleanup purpose.
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]
Cc: [email protected]
Fixes: ac5047671758 ("hv_netvsc: Disable NAPI before closing the VMBus channel")
Signed-off-by: Souradeep Chakrabarti <[email protected]>
Reviewed-by: Dexuan Cui <[email protected]>
Reviewed-by: Haiyang Zhang <[email protected]>
---
V1 -> V2:
Changed commit message, added some more details on
napi NAPIF_STATE_SCHED bit set and reset.
---
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
On Tue, Jan 30, 2024 at 11:35:51PM -0800, Souradeep Chakrabarti wrote:
> 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.
>
> This caused hv_netvsc getting hung at napi_disable, when netvsc_probe()
> has finished running but nvdev->subchan_work has not started yet.
> netvsc_subchan_work() -> rndis_set_subchannel() has not created the
> sub-channels and because of that netvsc_sc_open() is not running.
> netvsc_remove() calls cancel_work_sync(&nvdev->subchan_work), for which
> netvsc_subchan_work did not run.
>
> netif_napi_add() sets the bit NAPI_STATE_SCHED because it ensures NAPI
> cannot be scheduled. Then netvsc_sc_open() -> napi_enable will clear the
> NAPIF_STATE_SCHED bit, so it can be scheduled. napi_disable() does the
> opposite.
>
> Now during netvsc_device_remove(), when napi_disable is called for those
> subchannels, napi_disable gets stuck on infinite msleep.
>
> This fix addresses this problem by ensuring that napi_disable() is not
> getting called for non-enabled NAPI struct.
> But netif_napi_del() is still necessary for these non-enabled NAPI struct
> for cleanup purpose.
>
> 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]
>
> Cc: [email protected]
> Fixes: ac5047671758 ("hv_netvsc: Disable NAPI before closing the VMBus channel")
> Signed-off-by: Souradeep Chakrabarti <[email protected]>
> Reviewed-by: Dexuan Cui <[email protected]>
> Reviewed-by: Haiyang Zhang <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Hello:
This patch was applied to netdev/net.git (main)
by Jakub Kicinski <[email protected]>:
On Tue, 30 Jan 2024 23:35:51 -0800 you wrote:
> 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.
>
> This caused hv_netvsc getting hung at napi_disable, when netvsc_probe()
> has finished running but nvdev->subchan_work has not started yet.
> netvsc_subchan_work() -> rndis_set_subchannel() has not created the
> sub-channels and because of that netvsc_sc_open() is not running.
> netvsc_remove() calls cancel_work_sync(&nvdev->subchan_work), for which
> netvsc_subchan_work did not run.
>
> [...]
Here is the summary with links:
- [V2,net] hv_netvsc: Fix race condition between netvsc_probe and netvsc_remove
https://git.kernel.org/netdev/net/c/e0526ec5360a
You are awesome, thank you!
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