From: Tao Liu <thomas.liu@ucloud.cn>
To: pshelar@ovn.org
Cc: dev@openvswitch.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, i.maximets@ovn.org,
jean.tourrilhes@hpe.com, kuba@kernel.org, davem@davemloft.net,
thomas.liu@ucloud.cn, wenxu@ucloud.cn
Subject: [ovs-dev] [PATCH net v2] openvswitch: meter: fix race when getting now_ms.
Date: Thu, 13 May 2021 21:08:00 +0800 [thread overview]
Message-ID: <20210513130800.31913-1-thomas.liu@ucloud.cn> (raw)
We have observed meters working unexpected if traffic is 3+Gbit/s
with multiple connections.
now_ms is not pretected by meter->lock, we may get a negative
long_delta_ms when another cpu updated meter->used, then:
delta_ms = (u32)long_delta_ms;
which will be a large value.
band->bucket += delta_ms * band->rate;
then we get a wrong band->bucket.
OpenVswitch userspace datapath has fixed the same issue[1] some
time ago, and we port the implementation to kernel datapath.
[1] https://patchwork.ozlabs.org/project/openvswitch/patch/20191025114436.9746-1-i.maximets@ovn.org/
Fixes: 96fbc13d7e77 ("openvswitch: Add meter infrastructure")
Signed-off-by: Tao Liu <thomas.liu@ucloud.cn>
Suggested-by: Ilya Maximets <i.maximets@ovn.org>
---
Changelog:
v2: just set negative long_delta_ms to zero in case of race for meter lock.
v1: make now_ms protected by meter lock.
---
net/openvswitch/meter.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/net/openvswitch/meter.c b/net/openvswitch/meter.c
index 96b524c..896b8f5 100644
--- a/net/openvswitch/meter.c
+++ b/net/openvswitch/meter.c
@@ -611,6 +611,14 @@ bool ovs_meter_execute(struct datapath *dp, struct sk_buff *skb,
spin_lock(&meter->lock);
long_delta_ms = (now_ms - meter->used); /* ms */
+ if (long_delta_ms < 0) {
+ /* This condition means that we have several threads fighting
+ * for a meter lock, and the one who received the packets a
+ * bit later wins. Assuming that all racing threads received
+ * packets at the same time to avoid overflow.
+ */
+ long_delta_ms = 0;
+ }
/* Make sure delta_ms will not be too large, so that bucket will not
* wrap around below.
--
1.8.3.1
next reply other threads:[~2021-05-13 13:08 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-13 13:08 Tao Liu [this message]
2021-05-13 14:35 ` [ovs-dev] [PATCH net v2] openvswitch: meter: fix race when getting now_ms Ilya Maximets
2021-05-13 23:00 ` patchwork-bot+netdevbpf
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