Clearing the pending state only has an effect if the IRQ state is
active-and-pending, which happens for edge-triggered interrupts if
another edge happens on the IRQ line for the currently active
interrupt. This window is small enough to ignore, at worst user
space will get another notification, which is harmless.
If unnecessary notifications are unwanted, the pending state should
be cleared during seL4_IRQHandler_Ack(), as that covers a much bigger
window. However, edge-triggered interrupts are not expected to happen
often. Making all interrupt handling slightly faster and the code
simpler is the better trade-off.
Reading the GIC config word is very slow for GICv2, see pull #1107.
Signed-off-by: Indan Zupancic <indan@nul.nu>
b4592ebc97