From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nicholas Piggin Subject: Re: [PATCH 1/2] lockdep: improve current->(hard|soft)irqs_enabled synchronisation with actual irq state Date: Thu, 23 Jul 2020 23:11:03 +1000 Message-ID: <1595506730.3mvrxktem5.astroid@bobo.none> References: <20200723105615.1268126-1-npiggin@gmail.com> <20200723114010.GO5523@worktop.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <20200723114010.GO5523@worktop.programming.kicks-ass.net> Sender: linux-kernel-owner@vger.kernel.org To: Peter Zijlstra Cc: Alexey Kardashevskiy , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Ingo Molnar , Will Deacon List-Id: linux-arch.vger.kernel.org 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: >=20 >> diff --git a/arch/powerpc/include/asm/hw_irq.h b/arch/powerpc/include/as= m/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) >=20 > 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=20 context though, for some reason. > That is, I recently > added suport for that on x86: >=20 > https://lkml.kernel.org/r/20200623083721.155449112@infradead.org > https://lkml.kernel.org/r/20200623083721.216740948@infradead.org >=20 > 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 patc= h=20 enables for x86 but at least it shouldn't be incompatible with this one=20 AFAIKS. Thanks, Nick From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37164 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727859AbgGWNLK (ORCPT ); Thu, 23 Jul 2020 09:11:10 -0400 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 References: <20200723105615.1268126-1-npiggin@gmail.com> <20200723114010.GO5523@worktop.programming.kicks-ass.net> In-Reply-To: <20200723114010.GO5523@worktop.programming.kicks-ass.net> MIME-Version: 1.0 Message-ID: <1595506730.3mvrxktem5.astroid@bobo.none> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: linux-arch-owner@vger.kernel.org List-ID: To: Peter Zijlstra Cc: Alexey Kardashevskiy , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Ingo Molnar , Will Deacon Message-ID: <20200723131103.-SvThe4PFX6IAdo3Ye9sbLr66Nr-CiBgd_afT9IidHk@z> 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: >=20 >> diff --git a/arch/powerpc/include/asm/hw_irq.h b/arch/powerpc/include/as= m/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) >=20 > 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=20 context though, for some reason. > That is, I recently > added suport for that on x86: >=20 > https://lkml.kernel.org/r/20200623083721.155449112@infradead.org > https://lkml.kernel.org/r/20200623083721.216740948@infradead.org >=20 > 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 patc= h=20 enables for x86 but at least it shouldn't be incompatible with this one=20 AFAIKS. Thanks, Nick