21.02/files/target/linux/mediatek/patches-5.4/999-2709-fix-race-inside-napi-enable.patch

From f57826291fc2ff833c01b39c01fa5b74b69485da Mon Sep 17 00:00:00 2001
From: Sam Shih <sam.shih@mediatek.com>
Date: Fri, 2 Jun 2023 13:06:29 +0800
Subject: [PATCH] [networking][999-2709-fix-race-inside-napi-enable.patch]

---
 net/core/dev.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 81892cd83..503af0034 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6413,12 +6413,16 @@ EXPORT_SYMBOL(napi_disable);
  */
 void napi_enable(struct napi_struct *n)
 {
-	BUG_ON(!test_bit(NAPI_STATE_SCHED, &n->state));
-	smp_mb__before_atomic();
-	clear_bit(NAPI_STATE_SCHED, &n->state);
-	clear_bit(NAPI_STATE_NPSVC, &n->state);
-	if (n->dev->threaded && n->thread)
-		set_bit(NAPI_STATE_THREADED, &n->state);
+	unsigned long val, new;
+
+	do {
+		val = READ_ONCE(n->state);
+		BUG_ON(!test_bit(NAPI_STATE_SCHED, &val));
+
+		new = val & ~(NAPIF_STATE_SCHED | NAPIF_STATE_NPSVC);
+		if (n->dev->threaded && n->thread)
+			new |= NAPIF_STATE_THREADED;
+	} while (cmpxchg(&n->state, val, new) != val);
 }
 EXPORT_SYMBOL(napi_enable);
 
-- 
2.34.1