[PATCH net v2 2/2] net: usb: cdc_mbim: don't enable BHs in tx_fixup under netpoll

[Nicolai Buchwitz <nb@tipi-net.de>]

cdc_mbim_tx_fixup() has the same spin_unlock_bh() as cdc_ncm_tx_fixup().
Under netpoll it runs pending softirqs while the txq lock is held, and
a transmit from one of them spins on that lock.

Use spin_lock_irqsave() as in cdc_ncm.

Fixes: 9bf211a30b3f ("net: cdc_mbim: adding MBIM driver")
Signed-off-by: Nicolai Buchwitz <nb@tipi-net.de>
---
 drivers/net/usb/cdc_mbim.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/usb/cdc_mbim.c b/drivers/net/usb/cdc_mbim.c
index a7010a0664c7d..7158716c1f106 100644
--- a/drivers/net/usb/cdc_mbim.c
+++ b/drivers/net/usb/cdc_mbim.c
@@ -223,6 +223,7 @@ static struct sk_buff *cdc_mbim_tx_fixup(struct usbnet *dev, struct sk_buff *skb
 	struct cdc_mbim_state *info = (void *)&dev->data;
 	struct cdc_ncm_ctx *ctx = info->ctx;
 	__le32 sign = cpu_to_le32(USB_CDC_MBIM_NDP16_IPS_SIGN);
+	unsigned long irqflags;
 	u16 tci = 0;
 	bool is_ip;
 	u8 *c;
@@ -289,9 +290,10 @@ static struct sk_buff *cdc_mbim_tx_fixup(struct usbnet *dev, struct sk_buff *skb
 		}
 	}
 
-	spin_lock_bh(&ctx->mtx);
+	/* IRQs are off and BHs on under netpoll, see cdc_ncm_tx_fixup() */
+	spin_lock_irqsave(&ctx->mtx, irqflags);
 	skb_out = cdc_ncm_fill_tx_frame(dev, skb, sign);
-	spin_unlock_bh(&ctx->mtx);
+	spin_unlock_irqrestore(&ctx->mtx, irqflags);
 	return skb_out;
 
 error:

-- 
2.53.0