Re: [PATCH v2 2/2] trace-cmd: Reset CPU mask to its default value with "trace-cmd reset".

[Tzvetomir Stoyanov <tz.stoyanov@gmail.com>]

On Tue, Oct 1, 2019 at 6:32 PM Steven Rostedt <rostedt@goodmis.org> wrote:
>
> On Tue,  1 Oct 2019 17:57:40 +0300
> "Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com> wrote:
>
> > "trace-cmd reset" command should put all ftrace config to its default
> > state, but trace cpumask was not reseted. The patch sets cpumask to
> > its default value - all CPUs are enabled for tracing.
> >
> > Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
> > ---
> >  tracecmd/trace-record.c | 35 +++++++++++++++++++++++++++++++++++
> >  1 file changed, 35 insertions(+)
> >
> > diff --git a/tracecmd/trace-record.c b/tracecmd/trace-record.c
> > index 69de82a..6f3520c 100644
> > --- a/tracecmd/trace-record.c
> > +++ b/tracecmd/trace-record.c
> > @@ -4096,6 +4096,40 @@ static void reset_clock(void)
> >               write_instance_file(instance, "trace_clock", "local", "clock");
> >  }
> >
> > +static void reset_cpu_mask(void)
> > +{
> > +     struct buffer_instance *instance;
> > +     int cpus = count_cpus();
> > +     int fullwords;
> > +     char *buf;
> > +     int bits;
> > +     int len;
> > +
> > +     fullwords = cpus / 32;
> > +     bits = cpus % 32;
> > +     len = (fullwords + 1) * 9;
> > +
> > +     buf = malloc(len + 1);
> > +     if (!buf) {
> > +             warning("Unable to allocate %d bytes for cpu mask", len + 1);
> > +             return;
> > +     }
> > +     buf[0] = '\0';
> > +     if (bits) {
> > +             sprintf(buf, "%x", (1 << bits) - 1);
> > +     } else if (fullwords) {
> > +             strcat(buf, "ffffffff");
> > +             fullwords--;
> > +     }
> > +     while (fullwords-- > 0)
> > +             strcat(buf, ",ffffffff");
>
> I like my way because it's a little more condensed ;-)
>
> But this works too and it's far from a fast path. As it's probably
> more readable, I'll all this one.
>
> -- Steve
>
Actually the only change here is to handle the case when bits is 0,
not to put the leading ",".
The ftrace complains with "Invalid argument" in that case.

>
> > +
> > +     for_all_instances(instance)
> > +             write_instance_file(instance, "tracing_cpumask", buf, "cpumask");
> > +
> > +     free(buf);
> > +}
> > +
> >  static void reset_event_pid(void)
> >  {
> >       add_event_pid("");
> > @@ -4808,6 +4842,7 @@ void trace_reset(int argc, char **argv)
> >       reset_clock();
> >       reset_event_pid();
> >       reset_max_latency_instance();
> > +     reset_cpu_mask();
> >       tracecmd_remove_instances();
> >       clear_func_filters();
> >       /* restore tracing_on to 1 */
>


-- 
Tzvetomir (Ceco) Stoyanov
VMware Open Source Technology Center