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    SubjectRe: [PATCH 3/3] tracing: Tracers that use CALLER_ADDR macros should select FRAME_POINTER
    From
    2009/2/4 Anton Vorontsov <avorontsov@ru.mvista.com>:
    > Irqsoff, switch and preempt tracers use CALLER_ADDR macros, so they
    > should select FRAME_POINTER. Otherwise traces are meaningless.
    >
    > Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
    > ---
    > kernel/trace/Kconfig | 3 +++
    > 1 files changed, 3 insertions(+), 0 deletions(-)
    >
    > diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
    > index e2a4ff6..48f7a37 100644
    > --- a/kernel/trace/Kconfig
    > +++ b/kernel/trace/Kconfig
    > @@ -86,6 +86,7 @@ config IRQSOFF_TRACER
    > select TRACE_IRQFLAGS
    > select TRACING
    > select TRACER_MAX_TRACE
    > + select FRAME_POINTER
    > help
    > This option measures the time spent in irqs-off critical
    > sections, with microsecond accuracy.
    > @@ -108,6 +109,7 @@ config PREEMPT_TRACER
    > depends on DEBUG_KERNEL
    > select TRACING
    > select TRACER_MAX_TRACE
    > + select FRAME_POINTER
    > help
    > This option measures the time spent in preemption off critical
    > sections, with microsecond accuracy.
    > @@ -136,6 +138,7 @@ config SCHED_TRACER
    > select TRACING
    > select CONTEXT_SWITCH_TRACER
    > select TRACER_MAX_TRACE
    > + select FRAME_POINTER
    > help
    > This tracer tracks the latency of the highest priority task
    > to be scheduled in, starting from the point it has woken up.
    > --


    Looks right.

    BTW, how behaves builtin_return_address in case of !FRAME_POINTERS ?
    I guess it would only work with the first caller builtin_return_address(0)


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