[RFC][PATCH] lockdep: WARN about local_irq_{en,dis}able in NMI context
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From: Peter Zijlstra on 6 Apr 2010 07:20 On Tue, 2010-04-06 at 02:50 -0700, David Miller wrote: > From: Frederic Weisbecker <fweisbec(a)gmail.com> > Date: Mon, 5 Apr 2010 21:40:58 +0200 > > > It happens without CONFIG_FUNCTION_TRACER as well (but it happens > > when the function tracer runs). And I hadn't your > > perf_arch_save_caller_regs() when I triggered this. > > I figured out the problem, it's NMIs. As soon as I disable all of the > NMI watchdog code, the problem goes away. > > This is because some parts of the NMI interrupt handling path are not > marked with "notrace" and the various tracer code paths use > local_irq_disable() (either directly or indirectly) which doesn't work > with sparc64's NMI scheme. These essentially turn NMIs back on in the > NMI handler before the NMI condition has been cleared, and thus we can > re-enter with another NMI interrupt. > > We went through this for perf events, and we just made sure that > local_irq_{enable,disable}() never occurs in any of the code paths in > perf events that can be reached via the NMI interrupt handler. (the > only one we had was sched_clock() and that was easily fixed) One thing we can do is make the code WARN about this, how about something like the below --- Subject: lockdep: WARN about local_irq_{en,dis}able in NMI context Some architectures implement NMIs by using IRQ priority levels and mixing local_irq_{en,dis}able() with NMIs will give unexpected results. Hence disallow this in general and WARN about it. Signed-off-by: Peter Zijlstra <a.p.zijlstra(a)chello.nl> --- kernel/lockdep.c | 10 ++++++++++ 1 files changed, 10 insertions(+), 0 deletions(-) diff --git a/kernel/lockdep.c b/kernel/lockdep.c index 08e6f76..06ec1c7 100644 --- a/kernel/lockdep.c +++ b/kernel/lockdep.c @@ -2341,6 +2341,11 @@ EXPORT_SYMBOL(trace_hardirqs_on_caller); void trace_hardirqs_on(void) { + /* + * Some architectures can't deal with local_irq_{enable,disable} + * from NMI context (SPARC), enforce this. + */ + WARN_ON_ONCE(in_nmi()); trace_hardirqs_on_caller(CALLER_ADDR0); } EXPORT_SYMBOL(trace_hardirqs_on); @@ -2375,6 +2380,11 @@ EXPORT_SYMBOL(trace_hardirqs_off_caller); void trace_hardirqs_off(void) { + /* + * Some architectures can't deal with local_irq_{enable,disable} + * from NMI context (SPARC), enforce this. + */ + WARN_ON_ONCE(in_nmi()); trace_hardirqs_off_caller(CALLER_ADDR0); } EXPORT_SYMBOL(trace_hardirqs_off); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |