In D22154#788672, @hselasky wrote:

If you look at:

void
_epoch_enter_preempt(epoch_t epoch, epoch_tracker_t et EPOCH_FILE_LINE)
{
...
        THREAD_NO_SLEEPING();

You find that in_epoch() implies THREAD_CAN_SLEEP() == 0 .

--HPS

In D22154#788671, @hselasky wrote:

I think a delmultitask would be appropriate to avoid races on the if_ioctl handler, adding and removing multicast addresses.

Regarding in_epoch() in non-sleepable context, this is not an issue. Entering and exiting epoch should not block or sleep.

Shouldn't the THREAD_CAN_SLEEP also check for in_epoch() test? I have come across threads that have the td_no_sleeping set to 0 and are inside an epoch section.

Shouldn't there be a similar fix for if_delmulti? This change only addresses if_addmulti. If the change is not required for if_delmulti, can you add the justification for why it is not required.

Shouldn't the state->flags be set before invoking print_instruction from inside print_address, i.e. before 2076?

Why is the function show_prerequisites removed?

The ifnet_sxlock lock is still present. Isn't that grabbed during the multicast code path? If so, shouldn't that be added to the lock order?

How about the lock order in subr_witness.c for IPv4 and Ipv6 multicast. Is it still required in the lock order?