From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH 1/2] lockdep: improve current->(hard|soft)irqs_enabled synchronisation with actual irq state Date: Thu, 23 Jul 2020 16:59:04 +0200 Message-ID: <20200723145904.GU5523@worktop.programming.kicks-ass.net> References: <20200723105615.1268126-1-npiggin@gmail.com> <20200723114010.GO5523@worktop.programming.kicks-ass.net> <1595506730.3mvrxktem5.astroid@bobo.none> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53912 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727885AbgGWO7N (ORCPT ); Thu, 23 Jul 2020 10:59:13 -0400 Content-Disposition: inline In-Reply-To: <1595506730.3mvrxktem5.astroid@bobo.none> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Nicholas Piggin Cc: Alexey Kardashevskiy , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Ingo Molnar , Will Deacon 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: > > 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. 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.