[Jaunty] [Karmic] Fix hostap interrupt handler oops on bootup

Tim Gardner tim.gardner at canonical.com
Wed Aug 19 15:42:35 UTC 2009

Colin Ian King wrote:
> https://bugs.launchpad.net/ubuntu/+bug/254837
> SRU Justification:
> Impact: Booting with the Senao NL-2511CD (PRISM II compatible) wireless
> card can generate a kernel oops in the hostap interrupt handler.
> Spurious shared interrupts or early probing interrupts can cause the
> hostap interrupt handler to oops before the driver has fully configured
> the IO base port addresses. In some cases the oops can be because
> the hardware shares an interrupt line, on other cases it is due to a
> race condition between probing for the hardware and configuring
> the IO base port. The latter occurs because the probing is required to
> determine the hardware port address which is only determined when the
> probe can interrupt the hardware (catch 22).
> Fix: This patch catches this pre-configured condition in the interrupt
> handler to avoid the oops.
> Testcase: Without the patch a kernel oops occurs on boot when the card
> is installed. With the patch, there is no kernel oops and the wireless
> card works.
> I originally started debugging this with a user on a Jaunty kernel, and
> now they have moved to Karmic. This patch will has been tested on Karmic
> by Dan Taylor Jr. and the patch will fix the problem for Jaunty too,
> c.f. https://bugs.launchpad.net/ubuntu/+bug/254837/comments/56
> Attached: The patch.

Does this really handle the case where the IRQ is shared? For example,
if hostap is chained in the front of the IRQ handlers list, it will
return IRQ_HANDLED every time. The next device in the chain will never
get an opportunity to service its devices and drive the IRQ level down.

Maybe you need some kind of counter that indicates "I've been here N
times, so I maybe its not my IRQ to dismiss".

Tim Gardner tim.gardner at canonical.com

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