Commit 61014292 authored by Committed by Linus TorvaldsBrowse files
[PATCH] x86_64 irq: Safely cleanup an irq after moving it.
The problem: After moving an interrupt when is it safe to teardown the data structures for receiving the interrupt at the old location? With a normal pci device it is possible to issue a read to a device to flush all posted writes. This does not work for the oldest ioapics because they are on a 3-wire apic bus which is a completely different data path. For some more modern ioapics when everything is using front side bus delivery you can flush interrupts by simply issuing a read to the ioapic. For other modern ioapics emperical testing has shown that this does not work. So it appears the only reliable way to know the last of the irqs from an ioapic have been received from before the ioapic was reprogrammed is to received the first irq from the ioapic from after it was reprogrammed. Once we know the last irq message has been received from an ioapic into a local apic we then need to know that irq message has been processed through the local apics. Signed-off-by: Eric W. Biederman <firstname.lastname@example.org> Signed-off-by: Linus Torvalds <email@example.com>
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