From 7a8174b7914912ccf6c327076d617a98a3a51667 Mon Sep 17 00:00:00 2001
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Wed, 16 Feb 2022 18:50:46 +0100
Subject: [PATCH] net: Correct wrong BH disable in hard-interrupt.

References: SLE Realtime Extension
Patch-mainline: v5.18-rc1
Git-commit: 167053f8dd0ed60287858448696b4784d7e1d899

I missed the obvious case where netif_ix() is invoked from hard-IRQ
context.

Disabling bottom halves is only needed in process context. This ensures
that the code remains on the current CPU and that the soft-interrupts
are processed at local_bh_enable() time.
In hard- and soft-interrupt context this is already the case and the
soft-interrupts will be processed once the context is left (at irq-exit
time).

Disable bottom halves if neither hard-interrupts nor soft-interrupts are
disabled. Update the kernel-doc, mention that interrupts must be enabled
if invoked from process context.

Fixes: baebdf48c3600 ("net: dev: Makes sure netif_rx() can be invoked in any context.")
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/r/Yg05duINKBqvnxUc@linutronix.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
 net/core/dev.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index a35de53e4c10..1d16cdede814 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5021,7 +5021,9 @@ EXPORT_SYMBOL(__netif_rx);
  *	congestion control or by the protocol layers.
  *	The network buffer is passed via the backlog NAPI device. Modern NIC
  *	driver should use NAPI and GRO.
- *	This function can used from any context.
+ *	This function can used from interrupt and from process context. The
+ *	caller from process context must not disable interrupts before invoking
+ *	this function.
  *
  *	return values:
  *	NET_RX_SUCCESS	(no congestion)
@@ -5030,13 +5032,16 @@ EXPORT_SYMBOL(__netif_rx);
  */
 int netif_rx(struct sk_buff *skb)
 {
+	bool need_bh_off = !(hardirq_count() | softirq_count());
 	int ret;
 
-	local_bh_disable();
+	if (need_bh_off)
+		local_bh_disable();
 	trace_netif_rx_entry(skb);
 	ret = netif_rx_internal(skb);
 	trace_netif_rx_exit(ret);
-	local_bh_enable();
+	if (need_bh_off)
+		local_bh_enable();
 	return ret;
 }
 EXPORT_SYMBOL(netif_rx);