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) <pet...@infradead.org>
---
arch/x86/Kconfig.debug | 3 +++
kernel/locking/lockdep.c | 8 +++++++-
lib/Kconfig.debug | 6 ++++++
3 files changed, 16 insertions(+), 1 deletion(-)
--- 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
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3712,6 +3712,9 @@ void noinstr lockdep_hardirqs_on(unsigne
* 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(unsign
* 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;
/*
--- 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
