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[110.174.173.27]) by smtp.gmail.com with ESMTPSA id 204sm2598009pfx.3.2020.07.23.03.56.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Jul 2020 03:56:25 -0700 (PDT) From: Nicholas Piggin To: linux-kernel@vger.kernel.org Cc: Nicholas Piggin , linux-arch@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Peter Zijlstra , Ingo Molnar , Will Deacon , Alexey Kardashevskiy Subject: [PATCH 1/2] lockdep: improve current->(hard|soft)irqs_enabled synchronisation with actual irq state Date: Thu, 23 Jul 2020 20:56:14 +1000 Message-Id: <20200723105615.1268126-1-npiggin@gmail.com> X-Mailer: git-send-email 2.23.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If an interrupt is not masked by local_irq_disable (e.g., a powerpc perf interrupt), then it can hit in local_irq_enable() after trace_hardirqs_on() and before raw_local_irq_enable(). If that interrupt handler calls local_irq_save(), it will call trace_hardirqs_off() but the local_irq_restore() will not call trace_hardirqs_on() again because raw_irqs_disabled_flags(flags) is true. This can lead lockdep_assert_irqs_enabled() to trigger false positive warnings. Fix this by being careful to only enable and disable trace_hardirqs with the outer-most irq enable/disable. Reported-by: Alexey Kardashevskiy Signed-off-by: Nicholas Piggin --- I haven't tested on other architectures but I imagine NMIs in general might cause a similar problem. Other architectures might have to be updated for patch 2, but there's a lot of asm around interrupt/return, so I didn't have a very good lock. The warnings should be harmless enough and uncover most places that need updating. arch/powerpc/include/asm/hw_irq.h | 11 ++++------- include/linux/irqflags.h | 29 ++++++++++++++++++----------- 2 files changed, 22 insertions(+), 18 deletions(-) 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) #else #define powerpc_local_irq_pmu_save(flags) \ diff --git a/include/linux/irqflags.h b/include/linux/irqflags.h index 6384d2813ded..571ee29ecefc 100644 --- a/include/linux/irqflags.h +++ b/include/linux/irqflags.h @@ -163,26 +163,33 @@ do { \ * if !TRACE_IRQFLAGS. */ #ifdef CONFIG_TRACE_IRQFLAGS -#define local_irq_enable() \ - do { trace_hardirqs_on(); raw_local_irq_enable(); } while (0) -#define local_irq_disable() \ - do { raw_local_irq_disable(); trace_hardirqs_off(); } while (0) +#define local_irq_enable() \ + do { \ + trace_hardirqs_on(); \ + raw_local_irq_enable(); \ + } while (0) + +#define local_irq_disable() \ + do { \ + bool was_disabled = raw_irqs_disabled(); \ + raw_local_irq_disable(); \ + if (!was_disabled) \ + trace_hardirqs_off(); \ + } while (0) + #define local_irq_save(flags) \ do { \ raw_local_irq_save(flags); \ - trace_hardirqs_off(); \ + if (!raw_irqs_disabled_flags(flags)) \ + trace_hardirqs_off(); \ } while (0) #define local_irq_restore(flags) \ do { \ - if (raw_irqs_disabled_flags(flags)) { \ - raw_local_irq_restore(flags); \ - trace_hardirqs_off(); \ - } else { \ + if (!raw_irqs_disabled_flags(flags)) \ trace_hardirqs_on(); \ - raw_local_irq_restore(flags); \ - } \ + raw_local_irq_restore(flags); \ } while (0) #define safe_halt() \ -- 2.23.0