Messages in this thread |  | | Date | Thu, 23 Jul 2020 23:11:03 +1000 | From | Nicholas Piggin <> | Subject | Re: [PATCH 1/2] lockdep: improve current->(hard|soft)irqs_enabled synchronisation with actual irq state |
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Excerpts from Peter Zijlstra's message of July 23, 2020 9:40 pm: > On Thu, Jul 23, 2020 at 08:56:14PM +1000, Nicholas Piggin wrote: > >> diff --git a/arch/powerpc/include/asm/hw_irq.h b/arch/powerpc/include/asm/hw_irq.h >> index 3a0db7b0b46e..35060be09073 100644 >> --- a/arch/powerpc/include/asm/hw_irq.h >> +++ b/arch/powerpc/include/asm/hw_irq.h >> @@ -200,17 +200,14 @@ static inline bool arch_irqs_disabled(void) >> #define powerpc_local_irq_pmu_save(flags) \ >> do { \ >> raw_local_irq_pmu_save(flags); \ >> - trace_hardirqs_off(); \ >> + if (!raw_irqs_disabled_flags(flags)) \ >> + trace_hardirqs_off(); \ >> } while(0) >> #define powerpc_local_irq_pmu_restore(flags) \ >> do { \ >> - if (raw_irqs_disabled_flags(flags)) { \ >> - raw_local_irq_pmu_restore(flags); \ >> - trace_hardirqs_off(); \ >> - } else { \ >> + if (!raw_irqs_disabled_flags(flags)) \ >> trace_hardirqs_on(); \ >> - raw_local_irq_pmu_restore(flags); \ >> - } \ >> + raw_local_irq_pmu_restore(flags); \ >> } while(0) > > You shouldn't be calling lockdep from NMI context!
After this patch it doesn't.
trace_hardirqs_on/off implementation appears to expect to be called in NMI context though, for some reason.
> That is, I recently > added suport for that on x86: > > https://lkml.kernel.org/r/20200623083721.155449112@infradead.org > https://lkml.kernel.org/r/20200623083721.216740948@infradead.org > > But you need to be very careful on how you order things, as you can see > the above relies on preempt_count() already having been incremented with > NMI_MASK.
Hmm. My patch seems simpler.
I don't know this stuff very well, I don't really understand what your patch enables for x86 but at least it shouldn't be incompatible with this one AFAIKS.
Thanks, Nick
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