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

[Masami Hiramatsu]

On Mon, 10 Feb 2020 17:18:01 -0500
Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:

> On Fri, 7 Feb 2020 15:14:56 +0900
> Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote:
> 
> > On Thu,  6 Feb 2020 15:09:19 +0000
> > Alan Maguire <alan.maguire@xxxxxxxxxx> 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@xxxxxxxxxx>
> > 
> > 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@xxxxxxxxxx>
> > > ---
> > >  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?

Oops, I missed to fill the comment. I meant

"but can you consider to use /proc/sys directly instead of sysctl command,
because other test cases uses /proc/sys (ftrace/fgraph-filter-stack.tc and
ftrace/func_stack_tracer.tc)?"

Thank you,

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


-- 
Masami Hiramatsu <mhiramat@xxxxxxxxxx>