| Message ID | 20210513130800.31913-1-thomas.liu@ucloud.cn (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | e4df1b0c24350a0f00229ff895a91f1072bd850d |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [ovs-dev,net,v2] openvswitch: meter: fix race when getting now_ms. | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | success | Link |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Clearly marked for net |
| netdev/subject_prefix | success | Link |
| netdev/cc_maintainers | fail | 1 blamed authors not CCed: azhou@ovn.org; 1 maintainers not CCed: azhou@ovn.org |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 0 this patch: 0 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 14 lines checked |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 0 this patch: 0 |
| netdev/header_inline | success | Link |
On 5/13/21 3:08 PM, Tao Liu wrote: > 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. > --- Thanks! I didn't test it, but the change looks good to me. Reviewed-by: Ilya Maximets <i.maximets@ovn.org> > 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. >
Hello: This patch was applied to netdev/net.git (refs/heads/master): On Thu, 13 May 2021 21:08:00 +0800 you wrote: > 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. > > [...] Here is the summary with links: - [ovs-dev,net,v2] openvswitch: meter: fix race when getting now_ms. https://git.kernel.org/netdev/net/c/e4df1b0c2435 You are awesome, thank you! -- Deet-doot-dot, I am a bot. https://korg.docs.kernel.org/patchwork/pwbot.html
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.
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(+)