Re: [PATCH RT] add pending in fasteoi for IOAPIC hack

[Jon Masters <jcm@redhat.com>]

On Wed, 2007-12-12 at 15:41 -0500, Steven Rostedt wrote:
> The IOAPIC hack that does a level=>edge to mask does not disable
> interrupts. So we can receive interrupts when masked, and this means
> that we can miss interrupts that arrive when the thread is handling
> them.
> 
> This patch adds the "IRQ_PENDING" logic of the edge irqs to be
> able to catch interrupts coming in when supposably "masked".

ACK on all of these. I've been using them internally for a bit in
pursuit of a later problem. Additionally, I am currently reworking the
level->edge->level hack because it's known to be in violation of a
number of errata from third parties. The "legacy mode" hack is actually
only need on certain systems, which have e.g. a PCIe host bridge with
integrated IO-APIC that snoops the APIC to determine mask status.

I'm going to add a blacklist and quirks instead, as doing
level->edge->level otherwise causes us to start losing interrupts on
other systems. I will supply more information later - this is a somewhat
involved problem that we (Red Hat) have been looking at for a while.

Jon.