SMP.
We used to route all PIC based interrupts to cpu 0, and used the per-CPU
interrupt mask to enable/disable interrupts. But the interrupt threads can
run on any cpu on SMP, and the interrupt thread will re-enable the interrupts
on the CPU it runs on when it is done, and not on cpu0 where the PIC will
still send interrupts to.
The fix is move the disable/enable for PIC based interrupts to PIC, we will
ack on PIC only when the interrupt thread is done, and we do not use the
per-CPU interrupt mask.
The changes also introduce a way for subsystems to add a function that
will be called to clear the interrupt on the subsystem. Currently This is
used by the PCI/PCIe for doing additional work during the interrupt
handling.
b47f51b4a0