From ed00495333ccc80fc8fb86fb43773c3c2a499466 Mon Sep 17 00:00:00 2001 From: "peterz@infradead.org" Date: Mon, 27 Jul 2020 14:48:52 +0200 Subject: locking/lockdep: Fix TRACE_IRQFLAGS vs. NMIs Prior to commit: 859d069ee1dd ("lockdep: Prepare for NMI IRQ state tracking") IRQ state tracking was disabled in NMIs due to nmi_enter() doing lockdep_off() -- with the obvious requirement that NMI entry call nmi_enter() before trace_hardirqs_off(). [ AFAICT, PowerPC and SH violate this order on their NMI entry ] However, that commit explicitly changed lockdep_hardirqs_*() to ignore lockdep_off() and breaks every architecture that has irq-tracing in it's NMI entry that hasn't been fixed up (x86 being the only fixed one at this point). The reason for this change is that by ignoring lockdep_off() we can: - get rid of 'current->lockdep_recursion' in lockdep_assert_irqs*() which was going to to give header-recursion issues with the seqlock rework. - allow these lockdep_assert_*() macros to function in NMI context. Restore the previous state of things and allow an architecture to opt-in to the NMI IRQ tracking support, however instead of relying on lockdep_off(), rely on in_nmi(), both are part of nmi_enter() and so over-all entry ordering doesn't need to change. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20200727124852.GK119549@hirez.programming.kicks-ass.net --- arch/x86/Kconfig.debug | 3 +++ kernel/locking/lockdep.c | 8 +++++++- lib/Kconfig.debug | 6 ++++++ 3 files changed, 16 insertions(+), 1 deletion(-) diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug index 0dd319e6e5b4..ee1d3c5834c6 100644 --- a/arch/x86/Kconfig.debug +++ b/arch/x86/Kconfig.debug @@ -3,6 +3,9 @@ config TRACE_IRQFLAGS_SUPPORT def_bool y +config TRACE_IRQFLAGS_NMI_SUPPORT + def_bool y + config EARLY_PRINTK_USB bool diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index d595623c4b34..8b0b28b4546b 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -3712,6 +3712,9 @@ void noinstr lockdep_hardirqs_on(unsigned long ip) * and not rely on hardware state like normal interrupts. */ if (unlikely(in_nmi())) { + if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI)) + return; + /* * Skip: * - recursion check, because NMI can hit lockdep; @@ -3773,7 +3776,10 @@ void noinstr lockdep_hardirqs_off(unsigned long ip) * they will restore the software state. This ensures the software * state is consistent inside NMIs as well. */ - if (unlikely(!in_nmi() && (current->lockdep_recursion & LOCKDEP_RECURSION_MASK))) + if (in_nmi()) { + if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI)) + return; + } else if (current->lockdep_recursion & LOCKDEP_RECURSION_MASK) return; /* diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 9ad9210d70a1..fa964b51f066 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1325,11 +1325,17 @@ config WW_MUTEX_SELFTEST endmenu # lock debugging config TRACE_IRQFLAGS + depends on TRACE_IRQFLAGS_SUPPORT bool help Enables hooks to interrupt enabling and disabling for either tracing or lock debugging. +config TRACE_IRQFLAGS_NMI + def_bool y + depends on TRACE_IRQFLAGS + depends on TRACE_IRQFLAGS_NMI_SUPPORT + config STACKTRACE bool "Stack backtrace support" depends on STACKTRACE_SUPPORT -- cgit v1.2.3