netdev - [PATCH net-next 5/6] net: adopt try_cmpxchg() in napi

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Date:   Tue, 15 Nov 2022 09:11:00 +0000
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com,
        Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 5/6] net: adopt try_cmpxchg() in napi_{enable|disable}()

This makes code a bit cleaner.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/core/dev.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 0c12c7ad04f21da05fef4c60ca5570bff48ec491..fb943dad96513e0f9eb1c3ce30c5bb7170edea5e 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6397,8 +6397,8 @@ void napi_disable(struct napi_struct *n)
 	might_sleep();
 	set_bit(NAPI_STATE_DISABLE, &n->state);
 
-	for ( ; ; ) {
-		val = READ_ONCE(n->state);
+	val = READ_ONCE(n->state);
+	do {
 		if (val & (NAPIF_STATE_SCHED | NAPIF_STATE_NPSVC)) {
 			usleep_range(20, 200);
 			continue;
@@ -6406,10 +6406,7 @@ void napi_disable(struct napi_struct *n)
 
 		new = val | NAPIF_STATE_SCHED | NAPIF_STATE_NPSVC;
 		new &= ~(NAPIF_STATE_THREADED | NAPIF_STATE_PREFER_BUSY_POLL);
-
-		if (cmpxchg(&n->state, val, new) == val)
-			break;
-	}
+	} while (!try_cmpxchg(&n->state, &val, new));
 
 	hrtimer_cancel(&n->timer);
 
@@ -6426,16 +6423,15 @@ EXPORT_SYMBOL(napi_disable);
  */
 void napi_enable(struct napi_struct *n)
 {
-	unsigned long val, new;
+	unsigned long new, val = READ_ONCE(n->state);
 
 	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);
+	} while (!try_cmpxchg(&n->state, &val, new));
 }
 EXPORT_SYMBOL(napi_enable);
 
-- 
2.38.1.431.g37b22c650d-goog