In the Linux kernel, the following vulnerability has been resolved:
ipv6: mcast: remove one synchronizenet() barrier in ipv6mc_down()
As discussed in the past (commit 2d3916f31891 ("ipv6: fix skb drops in igmp6eventquery() and igmp6eventreport()")) I think the synchronizenet() call in ipv6mc_down() is not needed.
Under load, synchronize_net() can last between 200 usec and 5 ms.
KASAN seems to agree as well.