netdev - [PATCH net 2/2] r8169: disable interrupts also for GRO-scheduled NAPI

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Date: Tue, 14 May 2024 08:52:02 +0200
From: Heiner Kallweit <hkallweit1@...il.com>
To: Paolo Abeni <pabeni@...hat.com>, Jakub Kicinski <kuba@...nel.org>,
 Eric Dumazet <edumazet@...gle.com>, David Miller <davem@...emloft.net>,
 Realtek linux nic maintainers <nic_swsd@...ltek.com>
Cc: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
 Ken Milmore <ken.milmore@...il.com>
Subject: [PATCH net 2/2] r8169: disable interrupts also for GRO-scheduled NAPI

Ken reported that RTL8125b can lock up if gro_flush_timeout has the
default value of 20000 and napi_defer_hard_irqs is set to 0.
In this scenario device interrupts aren't disabled, what seems to
trigger some silicon bug under heavy load. I was able to reproduce this
behavior on RTL8168h.
Disabling device interrupts if NAPI is scheduled from a place other than
the driver's interrupt handler is a necessity in r8169, for other
drivers it may still be a performance optimization.

Fixes: 7274c4147afb ("r8169: don't try to disable interrupts if NAPI is scheduled already")
Reported-by: Ken Milmore <ken.milmore@...il.com>
Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
---
 drivers/net/ethernet/realtek/r8169_main.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
index e5ea827a2..01f0ca53d 100644
--- a/drivers/net/ethernet/realtek/r8169_main.c
+++ b/drivers/net/ethernet/realtek/r8169_main.c
@@ -4639,6 +4639,7 @@ static irqreturn_t rtl8169_interrupt(int irq, void *dev_instance)
 {
 	struct rtl8169_private *tp = dev_instance;
 	u32 status = rtl_get_events(tp);
+	int ret;
 
 	if ((status & 0xffff) == 0xffff || !(status & tp->irq_mask))
 		return IRQ_NONE;
@@ -4657,10 +4658,11 @@ static irqreturn_t rtl8169_interrupt(int irq, void *dev_instance)
 		rtl_schedule_task(tp, RTL_FLAG_TASK_RESET_PENDING);
 	}
 
-	if (napi_schedule_prep(&tp->napi)) {
+	ret = __napi_schedule_prep(&tp->napi);
+	if (ret >= 0)
 		rtl_irq_disable(tp);
+	if (ret > 0)
 		__napi_schedule(&tp->napi);
-	}
 out:
 	rtl_ack_events(tp, status);
 
-- 
2.45.0