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SubjectRe: [PATCH] softlockup: detect bottom-half lockups
Stumbled upon ftrace tracepoints while writing this patch. Should
make life a lot easier for debugging latency issues.

bhlockup should complement ftrace. Once you've found that there's a
problem, tracing can be a big help in debugging. But assertions are
nice for finding problems you didn't know exist.

Ingo Molnar (mingo@elte.hu) wrote:
>
> * Mandeep Singh Baines <msb@google.com> wrote:
>
> > The feature should be useful to real-time developers and developers of
> > network and other high-performance drivers.
>
> hm, did you know about the ftrace latency tracers:
>
> config IRQSOFF_TRACER
> bool "Interrupts-off Latency Tracer"
>
> config PREEMPT_TRACER
> bool "Preemption-off Latency Tracer"
>
> config SCHED_TRACER
> bool "Scheduling Latency Tracer"
>
> PREEMPT_TRACER would have shown you that softirqs-off section very nicely.
>
> (And if you also enable the function tracer then not just the latency
> endpoint is shown, but also all the function calls that happened in the
> critical section.)
>
> Ingo


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