On Wed, Apr 24, 2024 at 06:30:06PM -0400, Alan Stern wrote:
> On Wed, Apr 24, 2024 at 12:59:51PM -0700, Guenter Roeck wrote:
> > Testing ohci functionality with qemu's pci-ohci emulation often results
> > in ohci interface stalls, resulting in hung task timeouts.
> >
> > The problem is caused by lost interrupts between the emulation and the
> > Linux kernel code. Additional interrupts raised while the ohci interrupt
> > handler in Linux is running and before the handler clears the interrupt
> > status are not handled. The fix for a similar problem in ehci suggests
> > that the problem is likely caused by edge-triggered MSI interrupts. See
> > commit 0b60557230ad ("usb: ehci: Prevent missed ehci interrupts with
> > edge-triggered MSI") for details.
> >
> > Ensure that the ohci interrupt code handles all pending interrupts before
> > returning to solve the problem.
> >
> > Cc: Gerd Hoffmann <kraxel@xxxxxxxxxx>
> > Fixes: 306c54d0edb6 ("usb: hcd: Try MSI interrupts on PCI devices")
> > Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> > ---
> > v2: Only repeat if the interface is still active
>
> Reviewed-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
>
> Greg might insist that the patch be CC'ed to stable@xxxxxxxxxxxxxxx since
> it contains a Fixes: tag.
I'll add that by hand, no worries.
