I am not familiar with other architecture, but for ARM, Linux Kernel
2.6.35, i checked the function handle_level_irq()and handle_edge_irq() in
chip.c, both of them will call handle_IRQ_event() which is in handle.c. and
the function handle_IRQ_event() will call the interrupt handler written by
user. Kernel does not open interrupt(ARM CPSR I bit)when calling interrupt
handler in handle_IRQ_event() function. this is only for top-half interrupt
handling.? for bottom-half, it is no doubt that the interrupt will be
opened.

The same applies to 3.3.0 as I see from the code of handle_irq_event_percpu()
and its friends...

--- KostaZ