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    SubjectRe: [PATCH v7 2/2] tracing: Add support for preempt and irq enable/disable events
    On Fri, Sep 29, 2017 at 02:22:45PM -0700, Joel Fernandes wrote:
    > diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
    > index 0e3033c00474..515ac851841a 100644
    > --- a/kernel/trace/trace_irqsoff.c
    > +++ b/kernel/trace/trace_irqsoff.c
    > @@ -16,6 +16,9 @@
    >
    > #include "trace.h"
    >
    > +#define CREATE_TRACE_POINTS
    > +#include <trace/events/preemptirq.h>
    > +
    > #if defined(CONFIG_IRQSOFF_TRACER) || defined(CONFIG_PREEMPT_TRACER)
    > static struct trace_array *irqsoff_trace __read_mostly;
    > static int tracer_enabled __read_mostly;
    > @@ -776,27 +779,60 @@ static inline void tracer_preempt_on(unsigned long a0, unsigned long a1) { }
    > static inline void tracer_preempt_off(unsigned long a0, unsigned long a1) { }
    > #endif
    >
    > +/*
    > + * trace_hardirqs_off can be called even when IRQs are already off.

    In fact it must be.. otherwise you'll get a complaint.

    > It is
    > + * pointless and inconsistent with trace_preempt_enable and
    > + * trace_preempt_disable to trace this, lets prevent double counting it with a
    > + * per-cpu variable. Also reuse the per-cpu variable for other trace_hardirqs_*
    > + * functions since we already define it.

    Lockdep ignores redundant calls. But I'm not entirely sure what the
    above is trying to say.

    > + */
    > +static DEFINE_PER_CPU(int, tracing_irq_cpu);
    > +
    > #if defined(CONFIG_TRACE_IRQFLAGS) && !defined(CONFIG_PROVE_LOCKING)
    > void trace_hardirqs_on(void)
    > {
    > + if (!this_cpu_read(tracing_irq_cpu))
    > + return;
    > +
    > + trace_irq_enable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);
    > tracer_hardirqs_on();
    > +
    > + this_cpu_write(tracing_irq_cpu, 0);
    > }
    > EXPORT_SYMBOL(trace_hardirqs_on);
    >
    > void trace_hardirqs_off(void)
    > {
    > + if (this_cpu_read(tracing_irq_cpu))
    > + return;
    > +
    > + this_cpu_write(tracing_irq_cpu, 1);
    > +
    > + trace_irq_disable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);
    > tracer_hardirqs_off();
    > }
    > EXPORT_SYMBOL(trace_hardirqs_off);
    >
    > __visible void trace_hardirqs_on_caller(unsigned long caller_addr)
    > {
    > + if (!this_cpu_read(tracing_irq_cpu))
    > + return;
    > +
    > + trace_irq_enable_rcuidle(CALLER_ADDR0, caller_addr);
    > tracer_hardirqs_on_caller(caller_addr);
    > +
    > + this_cpu_write(tracing_irq_cpu, 0);
    > }
    > EXPORT_SYMBOL(trace_hardirqs_on_caller);
    >
    > __visible void trace_hardirqs_off_caller(unsigned long caller_addr)
    > {
    > + if (this_cpu_read(tracing_irq_cpu))
    > + return;
    > +
    > + this_cpu_write(tracing_irq_cpu, 1);
    > +
    > + trace_irq_disable_rcuidle(CALLER_ADDR0, caller_addr);
    > tracer_hardirqs_off_caller(caller_addr);
    > }
    > EXPORT_SYMBOL(trace_hardirqs_off_caller);

    lockdep implements the trace_hardirq_*() in terms of *_caller(). Would
    that make sense here?

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