Question about NIOS's irq line hold duration

Hello everyone,

I'm now working on a NIOS II project and something about NIOS Irq bothers me.

Just as the image shows, my questions are :

• How long should we keep the irq line high?
• Will irq handler quit if we let down the irq signal in the middle?(like t1)
• What would happen at t2?

I'm not sure if my question is clear enough. Tell me if you need further information.

Thanks a lot.