On Mon, Oct 16, 2023 at 12:56:24PM -0400, Steven Rostedt wrote:
> On Fri, 13 Oct 2023 13:17:52 -0400
> Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
>
> > --- a/drivers/usb/core/hcd-pci.c
> > +++ b/drivers/usb/core/hcd-pci.c
> > @@ -292,6 +292,14 @@ void usb_hcd_pci_remove(struct pci_dev *dev)
> > if (!hcd)
> > return;
> >
> > + /* Fake an interrupt request in order to give the driver a chance
> > + * to test whether the controller hardware has been removed (e.g.,
> > + * cardbus physical eject).
> > + */
> > + local_irq_disable();
> > + usb_hcd_irq(0, hcd);
> > + local_irq_enable();
> > +
> > usb_remove_hcd(hcd);
> > if (hcd->driver->flags & HCD_MEMORY) {
> > iounmap(hcd->regs);
> >
> > The local_irq_disable() is there so that the irq handler will be invoked
> > in the state that it expects (i.e., with interrupts disabled).
> > Apparently Meng's RT kernel doesn't like it when the handler then
> > calls spin_lock(); I don't know why.
>
> Because in RT, spin_lock()s are actually mutexes.
>
> In RT, interrupt handlers do not even run with interrupts disabled (they
> run as threads), so the assumption that they run with interrupts disabled
> on RT is incorrect. One hack would simply be:
>
> if (!IS_ENABLED(CONFIG_PREEMPT_RT))
> local_irq_disable();
> usb_hcd_irq(0, hcd);
> if (!IS_ENABLED(CONFIG_PREEMPT_RT))
> local_irq_enable();
>
> But that's rather ugly. We use to have that as a wrapper of just:
>
> local_irq_disable_nort();
>
> but I don't know if we removed that or not.
>
> Sebastian?
Thanks for the information. I guess a simple approach would be to add
the wrapper back in, since it's not present in the current kernel.
Alan Stern
