Interrupt Service Routines and Interrupt Enable Flag

Projects Programming
1

so gentlemen,

could you please confirm my understanding

so at the moment when program entering in ISR, all interrupts are disabled ISR(INT0_vect){ //here already cli(); ?

and when we exiting from ISR

ISR(){
...
} //here already sei(); ?
2

could someone answer to this question please ?

3

alexblade:
could you please confirm my understanding

Could you please not hijack?

alexblade:
so at the moment when program entering in ISR, all interrupts are disabled

Correct.

alexblade:
and when we exiting from ISR //here already sei(); ?

Practically speaking that is correct.

However, I believe disabling interrupts is delayed until after the next machine instruction completes which would make it possible for interrupts to be restored to a disabled state when the interrupt service routine returns.