On Thu, Jul 01, 2021 at 12:09:58AM +0200, Javier Martinez Canillas wrote: > On 6/30/21 10:30 PM, Bjorn Helgaas wrote: > > On Wed, Jun 30, 2021 at 09:59:58PM +0200, Javier Martinez Canillas wrote: > > [snip] > > >> But maybe you can also add a paragraph that mentions the > >> CONFIG_DEBUG_SHIRQ option and shared interrupts? That way, other > >> driver authors could know that by enabling this an underlying > >> problem might be exposed for them to fix. > > > > Good idea, thanks! I added this; is it something like what you > > had in mind? > > Thanks a lot for doing this rewording. I just have a small nit for > the text. > > > Found by enabling CONFIG_DEBUG_SHIRQ, which calls the IRQ > > handler when it is being unregistered. An error during the > > probe path might cause this unregistration and IRQ handler > > execution before the device or data structure init has > > finished. > > The IRQ handler is not called when unregistered, but it is called > when another handler for the shared IRQ is unregistered. In this > particular driver, both a "pcie-sys" and "pcie-client" handlers are > registered, then an error leads to "pcie-sys" being unregistered and > the handler for "pcie-client" being called. Is this really true? I think that would mean CONFIG_DEBUG_SHIRQ would not find this kind of bug unless we actually registered two or more handlers for the shared IRQ, but it's still a bug even only one handler is registered. Looking at __free_irq() [1], my impression is that "action" is what we're removing and action->handler() is the IRQ handler we call when CONFIG_DEBUG_SHIRQ, so it doesn't look like it's calling the remaining handlers after removing one of them. > So maybe the following instead? > > Found by enabling CONFIG_DEBUG_SHIRQ, which calls the IRQ > handlers when a handler for the shared IRQ is unregistered. An > error during the probe path might cause this unregistration and > handler execution before the device or data structure init has > finished. [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/irq/manage.c?id=v5.13#n1805
