On Fri, May 29, 2020 at 11:45:53AM -0700, Doug Anderson wrote: > Hi, > > On Fri, May 29, 2020 at 11:21 AM Frank Mori Hess <fmh6jj@xxxxxxxxx> wrote: > > > > On Fri, May 29, 2020 at 1:53 PM Doug Anderson <dianders@xxxxxxxxxxxx> wrote: > > > > > > > > I don't get it. A hypothetical machine could have literally anything > > > > sharing the IRQ line, right? > > > > > > It's not a real physical line, though? I don't think it's common to > > > have a shared interrupt between different IP blocks in a given SoC. > > > Even if it existed, all the drivers should disable their interrupts? > > > > I don't know, it's a hypothetical machine so it can be whatever you > > want. The driver requests shared irqs, if it doesn't actually support > > irq sharing, it shouldn't request them. > > I guess? As I understood it drivers have to be very carefully coded > up to support sharing their IRQ with someone else and I'm not > convinced dwc2 does that anyway. Certainly it doesn't hurt to keep > dwc2 clean, but until I see someone that's actually sharing dwc2's > interrupt and I can actually see an example I'm not sure I'm going to > spend too much time thinking about it. This is silly. If the driver says it supports shared IRQs, then it should actually support them. > > > > Anyways, my screaming interrupt occurs after a a new kernel has been > > > > booted with kexec. In this case, it doesn't matter if the old kernel > > > > called disable_irq or not. As soon as the new kernel re-enables the > > > > interrupt line, the kernel immediately disables it again with a > > > > backtrace due to the unhandled screaming interrupt. That's why the > > > > dwc2 hardware needs to have its interrupts turned off when the old > > > > kernel is shutdown. > > > > > > Isn't that a bug with your new kernel? I've seen plenty of bugs where > > > drivers enable their interrupt before their interrupt handler is set > > > to handle it. You never know what state the bootloader (or previous > > > kernel) might have left things in and if an interrupt was pending it > > > shouldn't kill you. > > > > It wouldn't hurt to add disabling of the dwc2 irq early in dwc2 > > initialization, > > More than it not hurting, I'd consider it a bug in the driver (and a > much more serious one than shutdown not disabling the interrupt). Normally the first thing a driver would do is reset the hardware, and that reset should disable any interrupt source. > > but why leave the irq screaming after shutdown? > > Sure. So I guess the answer is to just do both disable the interrupt > and make sure that the interrupt handler has finished. > > dwc2_disable_global_interrupts(hsotg); > disable_irq(hsotg->irq); Drivers with shared IRQs don't call disable_irq(); they call synchronize_irq(). It will do what you want (wait until all running handlers have returned). Alan Stern
