On Fri, Aug 09, 2019 at 10:28:15PM +0200, Lukas Wunner wrote: > On Fri, Aug 09, 2019 at 01:32:16PM -0600, Keith Busch wrote: > > On Fri, Aug 09, 2019 at 12:28:43PM +0200, Lukas Wunner wrote: > > > A sysfs request to enable or disable a PCIe hotplug slot should not > > > return before it has been carried out. That is sought to be achieved > > > by waiting until the controller's "pending_events" have been cleared. > > > > > > However the IRQ thread pciehp_ist() clears the "pending_events" before > > > it acts on them. If pciehp_sysfs_enable_slot() / _disable_slot() happen > > > to check the "pending_events" after they have been cleared but while > > > pciehp_ist() is still running, the functions may return prematurely > > > with an incorrect return value. > > > > > > Fix by introducing an "ist_running" flag which must be false before a > > > sysfs request is allowed to return. > > > > Can you instead just call synchronize_irq(ctrl->pcie->irq) after the > > pending events is cleared? > > You mean call synchronize_irq() from pciehp_sysfs_enable_slot() / > disable_slot()? That's a good idea, let me think that through and > try to make it work that way. After a bit of thinking: synchronize_irq() doesn't work for poll mode. A secondary concern is that if the IRQ is shared, synchronize_irq() waits for all the other (unrelated) IRQ threads to finish, i.e. longer than necessary. So I can't think of a better way to solve this. Thanks, Lukas
