Re: [PATCH 3/3] selftests/ftrace: Use /bin/echo instead of built-in echo

[Xiao Yang]

On 2020/5/7 17:15, Masami Hiramatsu wrote:
> On Thu, 7 May 2020 14:45:16 +0800
> Xiao Yang<yangx.jy@xxxxxxxxxxxxxx>  wrote:
>
> > On 2020/5/1 21:38, Masami Hiramatsu wrote:
> > > Since the built-in echo has different behavior in POSIX shell
> > > (dash) and bash, we forcibly use /bin/echo -E (not interpret
> > > backslash escapes) by default.
> > >
> > > This also fixes some test cases which expects built-in
> > > echo command.
> > >
> > > Reported-by: Liu Yiding<yidingx.liu@xxxxxxxxx>
> > > Signed-off-by: Masami Hiramatsu<mhiramat@xxxxxxxxxx>
> > > ---
> > >    tools/testing/selftests/ftrace/test.d/functions    |    3 +++
> > >    .../test.d/trigger/trigger-trace-marker-hist.tc    |    2 +-
> > >    .../trigger-trace-marker-synthetic-kernel.tc       |    4 ++++
> > >    .../trigger/trigger-trace-marker-synthetic.tc      |    4 ++--
> > >    4 files changed, 10 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/tools/testing/selftests/ftrace/test.d/functions b/tools/testing/selftests/ftrace/test.d/functions
> > > index 5d4550591ff9..ea59b6ea2c3e 100644
> > > --- a/tools/testing/selftests/ftrace/test.d/functions
> > > +++ b/tools/testing/selftests/ftrace/test.d/functions
> > > @@ -1,3 +1,6 @@
> > > +# Since the built-in echo has different behavior in POSIX shell (dash) and
> > > +# bash, we forcibly use /bin/echo -E (not interpret backslash escapes).
> > > +alias echo="/bin/echo -E"
> > Hi Masami, Steven
> >
> > It seems that only kprobe_syntax_errors.tc is impacted by the issue
> > currently.  Is it necessary for all tests to use /bin/echo and could we
> > just make kprobe_syntax_errors.tc use /bin/echo?
>
> Yes, I would like to unify the "echo"'s behavior among the testcases
> instead of patching each failure in the future.
> Or would you have any concern on it?
Hi Masami,

Very sorry for the late reply.

We may not avoid fixing related failures after your change:
1) We have to reuse built-in echo (do alias echo=echo) if we want to 
test common_pid for histogram.
2) We have to reuse built-in echo if some new tests want to interpret 
backslash escapes in future.

Is it simple to provide two implementations of echo?(built-in echo and 
echo command?) and then just apply echo command for kprobe_syntax_errors.tc?

BTW: My suggestion may not be correct.

Best Regards,
Xiao Yang
> Thank you,
>
> > Best Regards,
> > Xiao Yang
> >
> > >    clear_trace() { # reset trace output
> > >        echo>   trace
> > > diff --git a/tools/testing/selftests/ftrace/test.d/trigger/trigger-trace-marker-hist.tc b/tools/testing/selftests/ftrace/test.d/trigger/trigger-trace-marker-hist.tc
> > > index ab6bedb25736..b3f70f53ee69 100644
> > > --- a/tools/testing/selftests/ftrace/test.d/trigger/trigger-trace-marker-hist.tc
> > > +++ b/tools/testing/selftests/ftrace/test.d/trigger/trigger-trace-marker-hist.tc
> > > @@ -30,7 +30,7 @@ fi
> > >
> > >    echo "Test histogram trace_marker tigger"
> > >
> > > -echo 'hist:keys=common_pid'>   events/ftrace/print/trigger
> > > +echo 'hist:keys=ip'>   events/ftrace/print/trigger
> > >    for i in `seq 1 10` ; do echo "hello">   trace_marker; done
> > >    grep 'hitcount: *10$' events/ftrace/print/hist>   /dev/null || \
> > >        fail "hist trigger did not trigger correct times on trace_marker"
> > > diff --git a/tools/testing/selftests/ftrace/test.d/trigger/trigger-trace-marker-synthetic-kernel.tc b/tools/testing/selftests/ftrace/test.d/trigger/trigger-trace-marker-synthetic-kernel.tc
> > > index 18b4d1c2807e..c1625d945f4d 100644
> > > --- a/tools/testing/selftests/ftrace/test.d/trigger/trigger-trace-marker-synthetic-kernel.tc
> > > +++ b/tools/testing/selftests/ftrace/test.d/trigger/trigger-trace-marker-synthetic-kernel.tc
> > > @@ -44,6 +44,10 @@ echo 'latency u64 lat'>   synthetic_events
> > >    echo 'hist:keys=pid:ts0=common_timestamp.usecs'>   events/sched/sched_waking/trigger
> > >    echo 'hist:keys=common_pid:lat=common_timestamp.usecs-$ts0:onmatch(sched.sched_waking).latency($lat)'>   events/ftrace/print/trigger
> > >    echo 'hist:keys=common_pid,lat:sort=lat'>   events/synthetic/latency/trigger
> > > +
> > > +# We have to use the built-in echo here because waking up pid must be same
> > > +# as echoing pid.
> > > +alias echo=echo
> > >    sleep 1
> > >    echo "hello">   trace_marker
> > >
> > > diff --git a/tools/testing/selftests/ftrace/test.d/trigger/trigger-trace-marker-synthetic.tc b/tools/testing/selftests/ftrace/test.d/trigger/trigger-trace-marker-synthetic.tc
> > > index dd262d6d0db6..23e52c8d71de 100644
> > > --- a/tools/testing/selftests/ftrace/test.d/trigger/trigger-trace-marker-synthetic.tc
> > > +++ b/tools/testing/selftests/ftrace/test.d/trigger/trigger-trace-marker-synthetic.tc
> > > @@ -36,8 +36,8 @@ fi
> > >    echo "Test histogram trace_marker to trace_marker latency histogram trigger"
> > >
> > >    echo 'latency u64 lat'>   synthetic_events
> > > -echo 'hist:keys=common_pid:ts0=common_timestamp.usecs if buf == "start"'>   events/ftrace/print/trigger
> > > -echo 'hist:keys=common_pid:lat=common_timestamp.usecs-$ts0:onmatch(ftrace.print).latency($lat) if buf == "end"'>>   events/ftrace/print/trigger
> > > +echo 'hist:keys=ip:ts0=common_timestamp.usecs if buf == "start"'>   events/ftrace/print/trigger
> > > +echo 'hist:keys=ip:lat=common_timestamp.usecs-$ts0:onmatch(ftrace.print).latency($lat) if buf == "end"'>>   events/ftrace/print/trigger
> > >    echo 'hist:keys=common_pid,lat:sort=lat'>   events/synthetic/latency/trigger
> > >    echo -n "start">   trace_marker
> > >    echo -n "end">   trace_marker
> > >
> > >
> > >
> > > .