linux-kernel - [PATCH net v2] net: xilinx: axienet: Schedule NAPI in two steps

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Message-Id: <20240913145711.2284295-1-sean.anderson@linux.dev>
Date: Fri, 13 Sep 2024 10:57:11 -0400
From: Sean Anderson <sean.anderson@...ux.dev>
To: Radhey Shyam Pandey <radhey.shyam.pandey@....com>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org
Cc: linux-arm-kernel@...ts.infradead.org,
	Michal Simek <michal.simek@....com>,
	linux-kernel@...r.kernel.org,
	Robert Hancock <robert.hancock@...ian.com>,
	Sean Anderson <sean.anderson@...ux.dev>,
	Shannon Nelson <shannon.nelson@....com>
Subject: [PATCH net v2] net: xilinx: axienet: Schedule NAPI in two steps

As advised by Documentation/networking/napi.rst, masking IRQs after
calling napi_schedule can be racy. Avoid this by only masking/scheduling
if napi_schedule_prep returns true.

Fixes: 9e2bc267e780 ("net: axienet: Use NAPI for TX completion path")
Fixes: cc37610caaf8 ("net: axienet: implement NAPI and GRO receive")
Signed-off-by: Sean Anderson <sean.anderson@...ux.dev>
Reviewed-by: Shannon Nelson <shannon.nelson@....com>
---

Changes in v2:
- Don't use the irqoff variant of __napi_schedule

 drivers/net/ethernet/xilinx/xilinx_axienet_main.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
index 9eb300fc3590..3de6559ceea6 100644
--- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
+++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
@@ -1222,9 +1222,10 @@ static irqreturn_t axienet_tx_irq(int irq, void *_ndev)
 		u32 cr = lp->tx_dma_cr;
 
 		cr &= ~(XAXIDMA_IRQ_IOC_MASK | XAXIDMA_IRQ_DELAY_MASK);
-		axienet_dma_out32(lp, XAXIDMA_TX_CR_OFFSET, cr);
-
-		napi_schedule(&lp->napi_tx);
+		if (napi_schedule_prep(&lp->napi_tx)) {
+			axienet_dma_out32(lp, XAXIDMA_TX_CR_OFFSET, cr);
+			__napi_schedule(&lp->napi_tx);
+		}
 	}
 
 	return IRQ_HANDLED;
@@ -1266,9 +1267,10 @@ static irqreturn_t axienet_rx_irq(int irq, void *_ndev)
 		u32 cr = lp->rx_dma_cr;
 
 		cr &= ~(XAXIDMA_IRQ_IOC_MASK | XAXIDMA_IRQ_DELAY_MASK);
-		axienet_dma_out32(lp, XAXIDMA_RX_CR_OFFSET, cr);
-
-		napi_schedule(&lp->napi_rx);
+		if (napi_schedule_prep(&lp->napi_rx)) {
+			axienet_dma_out32(lp, XAXIDMA_RX_CR_OFFSET, cr);
+			__napi_schedule(&lp->napi_rx);
+		}
 	}
 
 	return IRQ_HANDLED;
-- 
2.35.1.1320.gc452695387.dirty