linux-kernel - Re: [PATCH v4 1/2] perf parse: Refactor struct perf_evsel_config

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Date:   Mon, 13 Jan 2020 23:21:03 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Mathieu Poirier <mathieu.poirier@...aro.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mike Leach <mike.leach@...aro.org>
Subject: Re: [PATCH v4 1/2] perf parse: Refactor struct perf_evsel_config_term

On Fri, Jan 10, 2020 at 04:04:10PM +0100, Jiri Olsa wrote:
> On Thu, Jan 09, 2020 at 09:34:24AM -0700, Mathieu Poirier wrote:
> 
> SNIP
> 
> > 
> > If we are to deal with all flields of the union, I think it should be as below:
> > 
> >         union {
> >                 bool            cfg_bool;
> >                 int             cfg_int;
> >                 unsigned long   cfg_ulong;
> >                 u32             cfg_u32;
> >                 char            *cfg_str;
> >         } val;
> > 
> > But just dealing with the "char *" as below would also be fine with me:
> > 
> >         union {
> >                 u64           period;
> >                 u64           freq;
> >                 bool          time;
> >                 u64           stack_user;
> >                 int           max_stack;
> >                 bool          inherit;
> >                 bool          overwrite;
> >                 unsigned long max_events;
> >                 bool          percore;
> >                 bool          aux_output;
> >                 u32           aux_sample_size;
> >                 u64           cfg_chg;
> >                 u64           num;
> >                 char          *str;
> >         } val;
> > 
> > > 
> > > struct perf_evsel_config_term {
> > >         struct list_head      list;
> > >         enum evsel_term_type  type;
> > >         union {
> > >                 u64           period;
> > >                 u64           freq;
> > >                 bool          time;
> > >                 char          *callgraph;
> > >                 char          *drv_cfg;
> > >                 u64           stack_user;
> > >                 int           max_stack;
> > >                 bool          inherit;
> > >                 bool          overwrite;
> > >                 char          *branch;
> > >                 unsigned long max_events;
> > >                 bool          percore;
> > >                 bool          aux_output;
> > >                 u32           aux_sample_size;
> > >                 u64           cfg_chg;
> > > +               u64           num;
> > > +               char          *str;
> > >         } val;
> > >         bool weak;
> > > };
> > > 
> > > > I will let Jiri make the
> > > > final call but if we are to proceed this way I think we should have a
> > > > member per type to avoid casting issues.
> > > 
> > > Yeah, let's see what's Jiri thinking.
> > > 
> > > Just note, with this change, I don't see any casting warning or errors
> > > when built perf on arm64/arm32.
> > 
> > At this time you may not, but they will happen and it will be very hard to
> > debug.
> 
> hi,
> sry for late reply..
> 
> I think ;-) we should either add all different types to the union
> or just add 'str' pointer to handle strings correctly.. which seems
> better, because it's less changes and there's no real issue that
> would need that other bigger change

Thanks for the suggestion, Jiri.

Have sent out patch v5 with following the ideas.

Thanks,
Leo Yan