bonding: annotate data-races arcound churn variables

bonding: annotate data-races arcound churn variables

These fields are updated asynchronously by the bonding state machine
in ad_churn_machine() while holding bond->mode_lock.

bond_info_show_slave() and bond_fill_slave_info() read them without
bond->mode_lock being held, we need to add READ_ONCE() and
WRITE_ONCE() annotations.

Note that AD_CHURN_MONITOR, AD_CHURN, and AD_NO_CHURN are defined
exclusively in (kernel private) include/net/bond_3ad.h header.

They should be moved to include/uapi/linux/if_bonding.h or userspace
tools will have to hardcode their values.

Fixes: 4916f2e2f3fc ("bonding: print churn state via netlink")
Fixes: 14c9551a32eb ("bonding: Implement port churn-machine (AD standard 43.4.17).")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260603123514.388226-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>