From 044d0d6de9f50192f9697583504a382347ee95ca Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Thu, 23 Jul 2020 20:56:14 +1000 Subject: [PATCH] lockdep: Only trace IRQ edges Problem: raw_local_irq_save(); // software state on local_irq_save(); // software state off ... local_irq_restore(); // software state still off, because we don't enable IRQs raw_local_irq_restore(); // software state still off, *whoopsie* existing instances: - lock_acquire() raw_local_irq_save() __lock_acquire() arch_spin_lock(&graph_lock) pv_wait() := kvm_wait() (same or worse for Xen/HyperV) local_irq_save() - trace_clock_global() raw_local_irq_save() arch_spin_lock() pv_wait() := kvm_wait() local_irq_save() - apic_retrigger_irq() raw_local_irq_save() apic->send_IPI() := default_send_IPI_single_phys() local_irq_save() Possible solutions: A) make it work by enabling the tracing inside raw_*() B) make it work by keeping tracing disabled inside raw_*() C) call it broken and clean it up now Now, given that the only reason to use the raw_* variant is because you don't want tracing. Therefore A) seems like a weird option (although it can be done). C) is tempting, but OTOH it ends up converting a _lot_ of code to raw just because there is one raw user, this strips the validation/tracing off for all the other users. So we pick B) and declare any code that ends up doing: raw_local_irq_save() local_irq_save() lockdep_assert_irqs_disabled(); broken. AFAICT this problem has existed forever, the only reason it came up is because commit: 859d069ee1dd ("lockdep: Prepare for NMI IRQ state tracking") changed IRQ tracing vs lockdep recursion and the first instance is fairly common, the other cases hardly ever happen. Signed-off-by: Nicholas Piggin [rewrote changelog] Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Steven Rostedt (VMware) Reviewed-by: Thomas Gleixner Acked-by: Rafael J. Wysocki Tested-by: Marco Elver Link: https://lkml.kernel.org/r/20200723105615.1268126-1-npiggin@gmail.com --- arch/powerpc/include/asm/hw_irq.h | 11 ++++------- include/linux/irqflags.h | 15 +++++++-------- 2 files changed, 11 insertions(+), 15 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 00d553d77911..3ed4e8771b64 100644 --- a/include/linux/irqflags.h +++ b/include/linux/irqflags.h @@ -191,25 +191,24 @@ do { \ #define local_irq_disable() \ do { \ + bool was_disabled = raw_irqs_disabled();\ raw_local_irq_disable(); \ - trace_hardirqs_off(); \ + 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() \