split out flag manipulation from general context manipulation in iflib

[kmacy]

Summary

To avoid blocking on the context lock in the swi thread and risk potential deadlocks, this change protects lighter weight updates that only need to be consistent with each other with their own lock.

[erj]

I don't see the console hanging on the version of ixl-iflib where I did see them when watchdogs happened, so this appears to fix the deadlock in that situation.

[kmacy]

In D14967#315442, @erj wrote:

I don't see the console hanging on the version of ixl-iflib where I did see them when watchdogs happened, so this appears to fix the deadlock in that situation.

Thanks for testing. +1

[sbruno]

Y'all want this committed?

[erj]

In D14967#315794, @sbruno wrote:

Y'all want this committed?

It looks like it!

[shurd]

Minor nit... I'm not sure if a race is actually possible here though.

sys/net/iflib.c

3738 ↗

(On Diff #41119)

This test should be inside the lock.

[kmacy]

• check watchdog and reset flags with lock held
• clear watchdog flag