On Thu, 06 Mar 2008 11:03:31 +1100 Benjamin Herrenschmidt <[EMAIL PROTECTED]> wrote:
> > > Yes, we are - it's the semaphore rewrite which is doing this in > > start_kernel(). It's being discussed. > > > > Enabling interrupts too early on powerpc was discovered to be fatal on > > powerpc years ago. It looks like that remains the case. > > Regarding these issues. I could make it non fatal and just WARN_ON, > provided that I have a way to differentiate legal vs. illegal calls > to local_irq_enable(). And local_irq_restore() and various other things. > We already have that function mostly out of > line in C code due to our lazy irq disabling scheme, so the overhead of > testing some global kernel state would be minimum here. > > However, I don't see anything around init/main.c:start_kernel() that I > can use. What do you reckon here we should do ? Add some kind of global > we set before calling local_irq_enable() ? Or make early_boot_irqs_on() > do that generically > > It's currently defined as an empty inline without CONFIG_TRACE_IRQFLAGS > but we could make it set a flag instead. > > I'm pretty sure other archs have similar problems, especially in the > embedded world where you are booted with random junk firmwares that may > leave devices, interrupt controllers etc... in random state, and > enabling incoming IRQs before the arch code properly initializes the > main interrupt controller can be fatal. I know at least of an ARM board > I worked on a while ago that had a similar issues. > > On ppc32, unfortunately, our local_irq_enable/restore are nice inlines > that whack the appropriate MSR bits directly, thus adding a test for a > global flag would add some bloat/overhead that I'd like to avoid, at > least until we decide to also do lazy disabling on those, if ever... I'd have thought that the way to do this would be to add it to lockdep - lockdep already has all the infrastructure and code sites to do this. Set some special flag saying its-ok-to-enable-interrupts-now and test that in lockdep. akpm:/usr/src/25> grep LOCKDEP arch/powerpc/Kconfig akpm:/usr/src/25> losers ;) Still, doing it for akpm:/usr/src/25> grep -l LOCKDEP arch/*/Kconfig arch/arm/Kconfig arch/avr32/Kconfig arch/mips/Kconfig arch/s390/Kconfig arch/sh/Kconfig arch/sparc64/Kconfig arch/um/Kconfig arch/x86/Kconfig should give pretty good coverage. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
