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locking/lockdep: Fix TRACE_IRQFLAGS vs. NMIs 

Prior to commit:

  859d069ee1 ("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) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200727124852.GK119549@hirez.programming.kicks-ass.net
This commit is contained in:
peterz@infradead.org 2020-07-27 14:48:52 +02:00 committed by Ingo Molnar
parent ba1f2b2eaa
commit ed00495333
3 changed files with 16 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
arch/x86/Kconfig.debug
View File

@ -3,6 +3,9 @@
config TRACE_IRQFLAGS_SUPPORT
def_bool y
config TRACE_IRQFLAGS_NMI_SUPPORT
def_bool y
config EARLY_PRINTK_USB
bool

8
kernel/locking/lockdep.c
View File

@ -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;
/*

6
lib/Kconfig.debug
View File

@ -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