Re: [PATCH] PCI: dwc: Fix interrupt race in when handling MSI

[Trent Piepho <tpiepho@impinj.com>]

On Tue, 2018-11-13 at 10:36 +0000, Lorenzo Pieralisi wrote:
> On Tue, Nov 13, 2018 at 01:18:41AM +0000, Trent Piepho wrote:
> 
> [...]
> 
> > > Based on the information provided, its very likely that I should
> > > use the
> > > PCIE_MSI_INTR0_MASK register instead of PCIE_MSI_INTR0_ENABLE on
> > > the
> > > dw_pci_bottom_mask() and dw_pci_bottom_unmask() callbacks. As
> > > soon as I return
> > > from Linux plumbers conference, I will test the system using the
> > > PCIE_MSI_INTR0_MASK register.
> > 
> > Using enable to mask the interrupt is broken.  It will allow an MSI
> > to
> > be lost if it arrives while the MSI in not enabled.  It is
> > impossible
> > to prevent that from racing against the pci device driver's final
> > check
> > that no MSI-signaled condition in the hardware is present.
> 
> That's exactly why I raised the point. I would like to understand if
> this means that this revert is not enough to fix the underlying issue
> or we need this revert AND correct mask/unmask operations.

Looks like _another_ bug added to the driver, this time in 4.17.