diff options
| author | peterz@infradead.org <peterz@infradead.org> | 2020-07-27 14:48:52 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2020-07-27 15:13:29 +0200 |
| commit | ed00495333ccc80fc8fb86fb43773c3c2a499466 (patch) | |
| tree | 64882e5a738ab148341521d4ac598038ce8afd81 | |
| parent | ba1f2b2eaa2a529dba722507c55ff3d761d325dd (diff) | |
| download | lwn-ed00495333ccc80fc8fb86fb43773c3c2a499466.tar.gz lwn-ed00495333ccc80fc8fb86fb43773c3c2a499466.zip | |
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) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200727124852.GK119549@hirez.programming.kicks-ass.net
| -rw-r--r-- | arch/x86/Kconfig.debug | 3 | ||||
| -rw-r--r-- | kernel/locking/lockdep.c | 8 | ||||
| -rw-r--r-- | lib/Kconfig.debug | 6 |
3 files changed, 16 insertions, 1 deletions
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 |