From: Nicholas Piggin <npiggin@gmail.com>
To: linux-kernel@vger.kernel.org
Cc: linux-arch@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>,
linuxppc-dev@lists.ozlabs.org,
Nicholas Piggin <npiggin@gmail.com>,
Alexey Kardashevskiy <aik@ozlabs.ru>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>
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 [thread overview]
Message-ID: <20200723105615.1268126-1-npiggin@gmail.com> (raw)
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 <aik@ozlabs.ru>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
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
next reply other threads:[~2020-07-23 10:58 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-23 10:56 Nicholas Piggin [this message]
2020-07-23 10:56 ` [PATCH 2/2] lockdep: warn on redundant or incorrect irq state changes Nicholas Piggin
2020-07-24 2:57 ` kernel test robot
2020-08-04 10:00 ` Alexey Kardashevskiy
2020-07-23 11:40 ` [PATCH 1/2] lockdep: improve current->(hard|soft)irqs_enabled synchronisation with actual irq state Peter Zijlstra
2020-07-23 13:11 ` Nicholas Piggin
2020-07-23 14:59 ` Peter Zijlstra
2020-07-23 16:20 ` Nicholas Piggin
2020-07-24 4:16 ` Alexey Kardashevskiy
2020-07-24 5:59 ` Nicholas Piggin
2020-07-26 7:40 ` Alexey Kardashevskiy
2020-07-24 6:16 ` Athira Rajeev
2020-07-24 2:19 ` kernel test robot
2020-07-24 3:15 ` kernel test robot
2020-07-25 20:26 ` Peter Zijlstra
2020-07-26 4:14 ` Nicholas Piggin
2020-07-26 11:59 ` peterz
2020-07-26 12:11 ` peterz
2020-07-28 11:22 ` Nicholas Piggin
2020-08-07 11:11 ` peterz
2020-08-12 8:18 ` Nicholas Piggin
2020-08-12 10:35 ` peterz
2020-08-18 7:22 ` Nicholas Piggin
2020-08-18 15:41 ` peterz
2020-08-18 23:54 ` Nicholas Piggin
2020-08-19 10:39 ` Alexey Kardashevskiy
2020-08-19 15:32 ` peterz
2020-08-19 15:39 ` peterz
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