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Date: Fri, 24 Jul 2020 14:16:39 +1000 From: Alexey Kardashevskiy <aik@...abs.ru> To: Nicholas Piggin <npiggin@...il.com>, Peter Zijlstra <peterz@...radead.org> Cc: linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org, Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org> Subject: Re: [PATCH 1/2] lockdep: improve current->(hard|soft)irqs_enabled synchronisation with actual irq state On 23/07/2020 23:11, Nicholas Piggin wrote: > 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. And your patches fix my error while Peter's do not: IRQs not enabled as expected WARNING: CPU: 0 PID: 1377 at /home/aik/p/kernel/kernel/softirq.c:169 __local_bh_enable_ip+0x118/0x190 > > 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 > -- Alexey
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