net: Fix a data-race around netdev_budget_usecs.

BugLink: https://bugs.launchpad.net/bugs/1991717
[ Upstream commit fa45d484c52c73f79db2c23b0cdfc6c6455093ad ]

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@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/net/core/dev.c b/net/core/dev.c
index fefe8ddd282fd05d28cc95cec9f8933a087ea342..276cca563325e1f52c04c8e9887bcdbc0e9e0589 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -7137,7 +7137,7 @@ 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);