Re: [PATCH 1/2] lockdep: improve current->(hard|soft)irqs_enabled synchronisation with actual irq state
From: Peter Zijlstra <peterz@infradead.org>
Date: 2020-07-23 14:59:17
Also in:
linux-arch, lkml
On Thu, Jul 23, 2020 at 11:11:03PM +1000, Nicholas Piggin wrote:
Excerpts from Peter Zijlstra's message of July 23, 2020 9:40 pm:quoted
On Thu, Jul 23, 2020 at 08:56:14PM +1000, Nicholas Piggin wrote:quoted
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.
You sure, trace_hardirqs_{on,off}() calls into lockdep. (FWIW they're
also broken vs entry ordering, but that's another story).
trace_hardirqs_on/off implementation appears to expect to be called in NMI context though, for some reason.
Hurpm, not sure.. I'll have to go grep arch code now :/ The generic NMI code didn't touch that stuff. Argh, yes, there might be broken there... damn! I'll go frob around.