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SubjectRe: timers: Make flags output in the timer_start tracepoint useful
On Fri, 10 Feb 2017, Steven Rostedt wrote:

> On Fri, 10 Feb 2017 14:25:03 +0100 (CET)
> Thomas Gleixner <tglx@linutronix.de> wrote:
>
> > The timer flags in the timer_start trace event contain lots of useful
> > information, but the meaning is not clear in the trace output because its
> > just printed as a hex value. Making tools rely on the bit positions is bad
> > as they might change over time.
> >
> > Decode the flags in the printout. Tools can retrieve the bits and their
> > meaning from the trace format file.
> >
> > Example output:
> > kworker/2:1-47 <SNIP> [timeout=592] cpu=2 idx=170 flags=D|I
> >
> > So the timer is Deferrable and Interruptsafe, queued on CPU 2 into bucket
> > 170.
> >
> > Requested-by: Arjan van de Ven <arjan@linux.intel.com>
> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> > ---
> > include/trace/events/timer.h | 14 ++++++++++++--
> > 1 file changed, 12 insertions(+), 2 deletions(-)
> >
> > --- a/include/trace/events/timer.h
> > +++ b/include/trace/events/timer.h
> > @@ -36,6 +36,13 @@ DEFINE_EVENT(timer_class, timer_init,
> > TP_ARGS(timer)
> > );
> >
> > +#define decode_timer_flags(flags) \
> > + __print_flags(flags, "|", \
> > + { TIMER_MIGRATING, "M" }, \
> > + { TIMER_DEFERRABLE, "D" }, \
> > + { TIMER_PINNED, "P" }, \
> > + { TIMER_IRQSAFE, "I" })
> > +
> > /**
> > * timer_start - called when the timer is started
> > * @timer: pointer to struct timer_list
> > @@ -65,9 +72,12 @@ TRACE_EVENT(timer_start,
> > __entry->flags = flags;
> > ),
> >
> > - TP_printk("timer=%p function=%pf expires=%lu [timeout=%ld] flags=0x%08x",
> > + TP_printk("timer=%p function=%pf expires=%lu [timeout=%ld] cpu=%u idx=%u flags=%s",
> > __entry->timer, __entry->function, __entry->expires,
> > - (long)__entry->expires - __entry->now, __entry->flags)
> > + (long)__entry->expires - __entry->now,
> > + __entry->flags & TIMER_CPUMASK,
> > + __entry->flags >> TIMER_ARRAYSHIFT,
> > + decode_timer_flags(__entry->flags & TIMER_TRACE_FLAGMASK))
>
> Hi Thomas,
>
> This all looks good, but I can't find TIMER_TRACE_FLAGMASK. Was that
> added by another patch?

-ENO_QUILT_REFRESH ....

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