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SubjectRe: timers: Make flags output in the timer_start tracepoint useful
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?

-- Steve

> );
>
> /**

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