"serious" foul by offended team during their advantage play

[Robert Goodman]

This is an offshoot of a thread in the football section.

Suppose one team knocks on, and while you're waiting to see if their opponents gain an advantage, the opposing team commits a foul of a more serious nature, some kind of dangerous play, but not enough to DQ or sin bin. Do you:

1. rule no advantage, go back to the knock-on and just warn the other player;
2. ignore the knock-on, and award the penalty kick at the spot of the dangerous play;
3. go back to the spot of the knock-on, and award the penalty for dangerous play there; or
4. something else?

Would you do the same thing if the original infraction were not an accidental knock-on but a non-dangerous obstruction?

Robert