linux-kernel - Re: timers: Make flags output in the timer

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Message-ID: <alpine.DEB.2.20.1702101536451.4036@nanos>
Date:   Fri, 10 Feb 2017 15:37:11 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Steven Rostedt <rostedt@...dmis.org>
cc:     LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Arjan van de Ven <arjan@...ux.intel.com>
Subject: Re: 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@...utronix.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@...ux.intel.com>
> > Signed-off-by: Thomas Gleixner <tglx@...utronix.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 ....