netdev - [PATCH v4 net 12/17] net: Fix a data-race around netdev_budget

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Message-ID: <20220823174700.88411-13-kuniyu@amazon.com>
Date:   Tue, 23 Aug 2022 10:46:55 -0700
From:   Kuniyuki Iwashima <kuniyu@...zon.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
CC:     Kuniyuki Iwashima <kuniyu@...zon.com>,
        Kuniyuki Iwashima <kuni1840@...il.com>,
        <netdev@...r.kernel.org>, Matthew Whitehead <tedheadster@...il.com>
Subject: [PATCH v4 net 12/17] net: Fix a data-race around netdev_budget_usecs.

While reading netdev_budget_usecs, it can be changed concurrently.
Thus, we need to add READ_ONCE() to its reader.

Fixes: 7acf8a1e8a28 ("Replace 2 jiffies with sysctl netdev_budget_usecs to enable softirq tuning")
Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
CC: Matthew Whitehead <tedheadster@...il.com>
---
 net/core/dev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index c83e23cfc57d..8221322d86db 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6665,7 +6665,7 @@ static __latent_entropy void net_rx_action(struct softirq_action *h)
 {
 	struct softnet_data *sd = this_cpu_ptr(&softnet_data);
 	unsigned long time_limit = jiffies +
-		usecs_to_jiffies(netdev_budget_usecs);
+		usecs_to_jiffies(READ_ONCE(netdev_budget_usecs));
 	int budget = READ_ONCE(netdev_budget);
 	LIST_HEAD(list);
 	LIST_HEAD(repoll);
-- 
2.30.2