From mboxrd@z Thu Jan 1 00:00:00 1970 From: Athira Rajeev Subject: Re: [PATCH 1/2] lockdep: improve current->(hard|soft)irqs_enabled synchronisation with actual irq state Date: Fri, 24 Jul 2020 11:46:26 +0530 Message-ID: <6BAF6D26-A316-4F0A-AF10-5E43B2C09B90@linux.vnet.ibm.com> References: <20200723105615.1268126-1-npiggin@gmail.com> <20200723114010.GO5523@worktop.programming.kicks-ass.net> <1595506730.3mvrxktem5.astroid@bobo.none> <1884dcea-9ecd-a1f3-21bb-213c655e2480@ozlabs.ru> Mime-Version: 1.0 (Mac OS X Mail 13.4 \(3608.80.23.2.2\)) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Return-path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:38160 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726178AbgGXGQu (ORCPT ); Fri, 24 Jul 2020 02:16:50 -0400 In-Reply-To: <1884dcea-9ecd-a1f3-21bb-213c655e2480@ozlabs.ru> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Alexey Kardashevskiy Cc: Nicholas Piggin , Peter Zijlstra , linux-arch@vger.kernel.org, Will Deacon , Ingo Molnar , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org > On 24-Jul-2020, at 9:46 AM, Alexey Kardashevskiy wrote: > > > > 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 Hi Nicholas, Alexey I was able to reproduce the warning which Alexey reported using perf_fuzzer test suite. With the patch provided by Nick, I don’t see the issue anymore. This patch fixes the warnings I got with perf fuzzer run. Thanks Nick for the fix. Tested-by: Athira Rajeev > > >> >> 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