linux-kernel - Re: [PATCH 1/2] ftrace/selftests: workaround cgroup RT scheduling issues

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Message-ID: <20200210171801.521e5faa@gandalf.local.home>
Date:   Mon, 10 Feb 2020 17:18:01 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Alan Maguire <alan.maguire@...cle.com>, shuah@...nel.org,
        mingo@...hat.com, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org, naveen.n.rao@...ux.vnet.ibm.com,
        colin.king@...onical.com
Subject: Re: [PATCH 1/2] ftrace/selftests: workaround cgroup RT scheduling
 issues

On Fri, 7 Feb 2020 15:14:56 +0900
Masami Hiramatsu <mhiramat@...nel.org> wrote:

> On Thu,  6 Feb 2020 15:09:19 +0000
> Alan Maguire <alan.maguire@...cle.com> wrote:
> 
> > wakeup_rt.tc and wakeup.tc tests in tracers/ subdirectory
> > fail due to the chrt command returning:
> > 
> >  chrt: failed to set pid 0's policy: Operation not permitted.
> > 
> > To work around this, temporarily disable grout RT scheduling
> > during ftracetest execution.  Restore original value on
> > test run completion.  With these changes in place, both
> > tests consistently pass.  
> 
> OK, this looks good to me.
> 
> Acked-by: Masami Hiramatsu <mhiramat@...nel.org>
> 
> Thanks!
> 
> > 
> > Fixes: c575dea2c1a5 ("selftests/ftrace: Add wakeup_rt tracer testcase")
> > Fixes: c1edd060b413 ("selftests/ftrace: Add wakeup tracer testcase")
> > Signed-off-by: Alan Maguire <alan.maguire@...cle.com>
> > ---
> >  tools/testing/selftests/ftrace/ftracetest | 23 +++++++++++++++++++++++
> >  1 file changed, 23 insertions(+)
> > 
> > diff --git a/tools/testing/selftests/ftrace/ftracetest b/tools/testing/selftests/ftrace/ftracetest
> > index 063ecb2..3207bbf 100755
> > --- a/tools/testing/selftests/ftrace/ftracetest
> > +++ b/tools/testing/selftests/ftrace/ftracetest
> > @@ -29,8 +29,26 @@ err_ret=1
> >  # kselftest skip code is 4
> >  err_skip=4
> >  
> > +# cgroup RT scheduling prevents chrt commands from succeeding, which
> > +# induces failures in test wakeup tests.  Disable for the duration of
> > +# the tests.
> > +sched_rt_runtime=$(sysctl -n kernel.sched_rt_runtime_us)  
> 
> OK, but can you 

??

Masami?

-- Steve

> 
> > +
> > +set_sysctl() {
> > +  sysctl -qw ${1}=${2} >/dev/null 2>&1
> > +}
> > +