Re: [tip:core/debug] debug lockups: Improve lockup detection

Andrew Morton
2009-08-02T19:41:13Z

On Sun, 2 Aug 2009 21:26:57 +0200 Ingo Molnar <mingo@elte.hu> wrote:

> > I think this just broke all non-x86 non-sparc SMP architectures.
>
> Yeah - it 'broke' them in the sense of them not having a working
> trigger_all_cpu_backtrace() implementation to begin with.

c'mon. It broke them in the sense that sysrq-l went from "works" to
"doesn't work".

It would take months for the relevant arch maintainers to even find out
about this, after which they're left with dud kernels out in the field.

It's better to break the build or to emit warnings than to silently and
secretly break their stuff.

--- a/include/linux/nmi.h~a
+++ a/include/linux/nmi.h
@@ -29,6 +29,9 @@ static inline void acpi_nmi_enable(void)
#endif

#ifndef trigger_all_cpu_backtrace
+#ifdef CONFIG_SMP
+#warning This architecture is missing a trigger_all_cpu_backtrace() implementation
+#endif
#define trigger_all_cpu_backtrace() do { } while (0)
#endif

_