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Date:   Wed, 23 Nov 2022 10:33:26 -0300
From:   Arnaldo Carvalho de Melo <acme@kernel.org>
To:     Ian Rogers <irogers@google.com>
Cc:     Christophe Leroy <christophe.leroy@csgroup.eu>,
        "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>,
        Ravi Bangoria <ravi.bangoria@amd.com>,
        "linux-perf-users@vger.kernel.org" <linux-perf-users@vger.kernel.org>,
        Disha Goel <disgoel@linux.vnet.ibm.com>,
        "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] perf test: Skip watchpoint tests if no watchpoints
 available
Message-ID: <Y34hJrqCzSE+W+X9@kernel.org>
References: <20221121102747.208289-1-naveen.n.rao@linux.vnet.ibm.com>
 <a9f0f8f1-96cd-f6a8-9dda-d4744b938f97@csgroup.eu>
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Em Tue, Nov 22, 2022 at 12:57:05PM -0800, Ian Rogers escreveu:
> On Tue, Nov 22, 2022 at 11:19 AM Christophe Leroy
> <christophe.leroy@csgroup.eu> wrote:
> >
> >
> >
> > Le 21/11/2022 ? 11:27, Naveen N. Rao a ?crit :
> > > On IBM Power9, perf watchpoint tests fail since no hardware breakpoints
> > > are available. Detect this by checking the error returned by
> > > perf_event_open() and skip the tests in that case.
> > >
> > > Reported-by: Disha Goel <disgoel@linux.vnet.ibm.com>
> > > Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
> > > ---
> > >   tools/perf/tests/wp.c | 12 +++++++-----
> > >   1 file changed, 7 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/tools/perf/tests/wp.c b/tools/perf/tests/wp.c
> > > index 56455da30341b4..cc8719609b19ea 100644
> > > --- a/tools/perf/tests/wp.c
> > > +++ b/tools/perf/tests/wp.c
> > > @@ -59,8 +59,10 @@ static int __event(int wp_type, void *wp_addr, unsigned long wp_len)
> > >       get__perf_event_attr(&attr, wp_type, wp_addr, wp_len);
> > >       fd = sys_perf_event_open(&attr, 0, -1, -1,
> > >                                perf_event_open_cloexec_flag());
> > > -     if (fd < 0)
> > > +     if (fd < 0) {
> > > +             fd = -errno;
> > >               pr_debug("failed opening event %x\n", attr.bp_type);
> > > +     }
> >
> > Do you really need that ?
> >
> > Can't you directly check errno in the caller ?
> 
> errno is very easily clobbered and not clearly set on success - ie,
> it'd be better not to do that.
> 
> Acked-by: Ian Rogers <irogers@google.com>

Thanks, applied.

- Arnaldo