Re: 2.6.9-rc4-mm1 : oops when rmmod uhci_hcd [was: 2.6.9-rc3-mm2 : oops...]

Alan Stern
2004-10-15T16:20:07Z

On Fri, 15 Oct 2004, Paul Fulghum wrote:

> This looks like it is related to the generic-irq-subsystem patches.
> Specifically, adding and removing proc entries for each interrupt.
>
> Laurent's configuration has two controllers sharing the same interrupt.
> The hcd->description for both controllers are identical: "uhci_hcd"
>
> This string is used when requesting the irq (hcd-pci.c).
> request_irq() creates a /proc/irq/nn/uhci_hcd entry.
> The IRQ action->dir (one for each device) is a pointer to this entry.
> There does not appear to be a check for name collision
> when creating this entry. So two identical entries are created,
> one for each device. The proc entries are added to the head of
> a list so the second entry is 1st in the list.
>
> When unloading the module, the proc entry is removed when free_irq()
> is called. Removal of the proc entry is based on name matching
> starting at the head of the list so the 2nd entry is found 1st.
> It looks like the proc entry of the second device is removed
> when calling free_irq() for the first device. When the
> second device is removed, the action->dir has already
> been freed causing the oops.
>
> Comments?

Your explanation sounds entirely reasonable to me. Can you pass it on to
the people responsible for the generic-irq subsystem?

Alan Stern