From: Tycho Andersen <tycho@tycho.ws>
To: Christian Brauner <christian@brauner.io>
Cc: "Serge E. Hallyn" <serge@hallyn.com>,
linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
luto@kernel.org, arnd@arndb.de, keescook@chromium.org,
akpm@linux-foundation.org, jannh@google.com, oleg@redhat.com,
cyphar@cyphar.com, viro@zeniv.linux.org.uk,
linux-fsdevel@vger.kernel.org, dancol@google.com,
timmurray@google.com, fweimer@redhat.com, tglx@linutronix.de,
x86@kernel.org, ebiederm@xmission.com
Subject: Re: [PATCH v7 2/2] selftests: add tests for pidfd_send_signal()
Date: Tue, 8 Jan 2019 11:25:54 -0700 [thread overview]
Message-ID: <20190108182554.GB28330@cisco> (raw)
In-Reply-To: <20190108182444.e6kq2gqftde23jou@brauner.io>
On Tue, Jan 08, 2019 at 07:24:46PM +0100, Christian Brauner wrote:
> On Tue, Jan 08, 2019 at 11:20:23AM -0700, Tycho Andersen wrote:
> > On Tue, Jan 08, 2019 at 12:17:42PM -0600, Serge E. Hallyn wrote:
> > > On Tue, Jan 08, 2019 at 10:58:43AM -0700, Tycho Andersen wrote:
> > > > On Tue, Jan 08, 2019 at 11:54:15AM -0600, Serge E. Hallyn wrote:
> > > > > On Tue, Jan 08, 2019 at 10:53:06AM -0700, Tycho Andersen wrote:
> > > > > > On Wed, Jan 02, 2019 at 05:16:54PM +0100, Christian Brauner wrote:
> > > > > > > + /*
> > > > > > > + * Stop the child so we can inspect whether we have
> > > > > > > + * recycled pid PID_RECYCLE.
> > > > > > > + */
> > > > > > > + close(pipe_fds[0]);
> > > > > > > + ret = kill(recycled_pid, SIGSTOP);
> > > > > > > + close(pipe_fds[1]);
> > > > > > > + if (ret) {
> > > > > > > + (void)wait_for_pid(recycled_pid);
> > > > > > > + _exit(PIDFD_ERROR);
> > > > > > > + }
> > > > > >
> > > > > > Sorry for being late to the party, but I wonder if this whole thing
> > > > > > couldn't be simplified with /proc/sys/kenrel/ns_last_pid?
> > > > >
> > > > > no, bc it's not namespaced :)
> > > >
> > > > Huh? It looks like it is...
> > > >
> > > > static int pid_ns_ctl_handler(struct ctl_table *table, int write,
> > > > void __user *buffer, size_t *lenp, loff_t *ppos)
> > > > {
> > > > struct pid_namespace *pid_ns = task_active_pid_ns(current);
> > > > struct ctl_table tmp = *table;
> > > > int ret, next;
> > > >
> > > > if (write && !ns_capable(pid_ns->user_ns, CAP_SYS_ADMIN))
> > > > return -EPERM;
> > > >
> > > > ...
> > >
> > > Oh - hah, but that's ns_last_pid. You'd want pid_max. And that one
> > > is not namespaced.
> >
> > Perhaps I'm misunderstanding, but isn't the point of all this code to
> > get the same pid again? So can't we just fork(), kill(), then set
> > ns_last_pid to pid-1, and fork() again to re-use?
>
> Maybe. It's just a selftest that works reliably as it is so unless
> there's a technical issue with the patch I'm not going to do another
> version just because of that unless people feel super strongly about
> this.
> Another advantage is that the code we have right now works even when
> CONFIG_CHECKPOINT_RESTORE is not selected.
No, it's fine as is. Just a lot less code if we do it the other way.
Cheers,
Tycho
next prev parent reply other threads:[~2019-01-08 18:25 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-02 16:16 [PATCH v7 1/2] signal: add pidfd_send_signal() syscall Christian Brauner
2019-01-02 16:16 ` [PATCH v7 2/2] selftests: add tests for pidfd_send_signal() Christian Brauner
2019-01-08 17:53 ` Tycho Andersen
2019-01-08 17:54 ` Serge E. Hallyn
2019-01-08 17:58 ` Tycho Andersen
2019-01-08 18:17 ` Serge E. Hallyn
2019-01-08 18:20 ` Tycho Andersen
2019-01-08 18:21 ` Serge E. Hallyn
2019-01-08 18:24 ` Christian Brauner
2019-01-08 18:25 ` Tycho Andersen [this message]
2019-01-08 23:47 ` [PATCH v7 1/2] signal: add pidfd_send_signal() syscall Christian Brauner
2019-02-15 5:00 ` Tycho Andersen
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