libteam September 2020

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[PATCH] Revert "teamd: Disregard current state when considering port enablement"
by Xin Long 16 Sep '20

16 Sep '20

This reverts commit deadb5b715227429a1879b187f5906b39151eca9. As Patrick noticed, with that commit, teamd_port_check_enable() would set the team port to the new state unconditionally, which triggers another change message from kernel to userspace, then teamd_port_check_enable() is called again to set the team port to the new state. This would go around and around to update the team port state, and even cause teamd to consume 100% cpu. As the issue caused by that commit is serious, it has to be reverted. As for the issued fixed by that commit, I would propose a new fix later. --- teamd/teamd_per_port.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/teamd/teamd_per_port.c b/teamd/teamd_per_port.c index 166da57..d429753 100644 --- a/teamd/teamd_per_port.c +++ b/teamd/teamd_per_port.c @@ -442,14 +442,18 @@ int teamd_port_check_enable(struct teamd_context *ctx, bool should_enable, bool should_disable) { bool new_enabled_state; + bool curr_enabled_state; int err; if (!teamd_port_present(ctx, tdport)) return 0; + err = teamd_port_enabled(ctx, tdport, &curr_enabled_state); + if (err) + return err; - if (should_enable) + if (!curr_enabled_state && should_enable) new_enabled_state = true; - else if (should_disable) + else if (curr_enabled_state && should_disable) new_enabled_state = false; else return 0; -- 2.1.0

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Re: [PATCH] teamd: Disregard current state when considering port enablement
by Xin Long 10 Sep '20

10 Sep '20

On Wed, Sep 2, 2020 at 9:25 PM Petr Machata <petrm(a)nvidia.com> wrote: > > > Xin Long <lucien.xin(a)gmail.com> writes: > > > do you have a reproducer for this race issue? > > I think they were spurious failures in > tools/testing/selftests/net/forwarding/mirror_gre_lag_lacp.sh run on a > simulated switch under qemu. This might work as an approximation: > > ./mirror_gre_lag_lacp.sh veth{5..12} > Hi, Petr, I couldn't reproduce it on my env. Can you please try with this kernel commit? commit 1c0522b4a2e143fa6e55e4bd2308415c81184ec7 Author: Petr Machata <petrm at mellanox.com> Date: Fri May 29 14:16:53 2020 +0300 selftests: forwarding: mirror_lib: Use mausezahn Thanks.

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Re: [PATCH] teamd: Disregard current state when considering port enablement
by Jiri Pirko 09 Sep '20

09 Sep '20

Wed, Nov 13, 2019 at 02:26:47PM CET, petrm(a)mellanox.com wrote: >On systems where carrier is gained very quickly, there is a race between >teamd and the kernel that sometimes leads to all team slaves being stuck in >enabled=false state. > >When a port is enslaved to a team device, the kernel sends a netlink >message marking the port as enabled. teamd's lb_event_watch_port_added() >calls team_set_port_enabled(false), because link is down at that point. The >kernel responds with a message marking the port as disabled. At this point, >there are two outstanding messages: the initial one marking port as >enabled, and the second one marking it as disabled. teamd has not processed >either of these. > >Next teamd gets the netlink message that sets enabled=true, and updates its >internal cache accordingly. If at this point ethtool link-watch wakes up, >teamd considers (in teamd_port_check_enable()) enabling the port. After >consulting the cache, it concludes the port is already up, and neglects to >do so. Only then does teamd get the netlink message informing it of setting >enabled=false. > >The problem is that the teamd cache is not synchronous with respect to the >kernel state. If the carrier takes a while to come up (as is normally the >case), this is not a problem, because teamd caches up quickly enough. But >this may not always be the case, and particularly on a simulated system, >the carrier is gained almost immediately. > >Fix this by not suppressing the enablement message. > >Signed-off-by: Petr Machata <petrm(a)mellanox.com> applied. Thanks!

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libteam September 2020