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Date:   Fri, 15 Nov 2019 16:14:20 +0100
From:   Adrian Reber <areber@redhat.com>
To:     Andrei Vagin <avagin@gmail.com>
Cc:     Christian Brauner <christian.brauner@ubuntu.com>,
        Eric Biederman <ebiederm@xmission.com>,
        Pavel Emelyanov <ovzxemul@gmail.com>,
        Jann Horn <jannh@google.com>, Oleg Nesterov <oleg@redhat.com>,
        Dmitry Safonov <0x7f454c46@gmail.com>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        linux-kernel@vger.kernel.org, Mike Rapoport <rppt@linux.ibm.com>,
        Radostin Stoyanov <rstoyanov1@gmail.com>
Subject: Re: [PATCH v10 2/2] selftests: add tests for clone3() with *set_tid
Message-ID: <20191115151420.GC20767@dcbz.redhat.com>
References: <20191114142707.1608679-1-areber@redhat.com>
 <20191114142707.1608679-2-areber@redhat.com>
 <20191114183421.GA171963@gmail.com>
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On Thu, Nov 14, 2019 at 10:34:21AM -0800, Andrei Vagin wrote:
> > +=09=09/*
> > +=09=09 * This should work and from the parent we should see
> > +=09=09 * something like 'NSpid:=09pid=0942=091'.
> > +=09=09 */
> > +=09=09test_clone3_set_tid(set_tid, 3, CLONE_NEWPID, 0, 42, true);
> > +
> > +=09=09_exit(ksft_cnt.ksft_pass);
> > +=09}
> > +
> > +=09close(pipe_1[1]);
> > +=09close(pipe_2[0]);
> > +=09while (read(pipe_1[0], &buf, 1) > 0) {
>=20
> If a child process will crash, this will be a busyloop.

No. To be honest the whole loop is unnecessary. If the loop is entered
there is immediately a break.

> > +=09=09ksft_print_msg("[%d] Child is ready and waiting\n", getpid());
> > +=09=09break;
> > +=09}

If the loop is not entered it does not loop. So the whole thing is
useless. I think I was expecting it to block, but it doesn't work that
way.

> > +=09snprintf(proc_path, sizeof(proc_path), "/proc/%d/status", pid);
> > +=09f =3D fopen(proc_path, "r");
> > +=09if (f =3D=3D NULL)
> > +=09=09ksft_exit_fail_msg(
> > +=09=09=09"%s - Could not open %s\n",
> > +=09=09=09strerror(errno), proc_path);

If the child does not exist anymore, the test will fail here and exit.

Besides this while() I tried to address all your comments in v11. Any
further comments on the test?

=09=09Adrian