From: "Enrico Weigelt, metux IT consult" <lkml@metux.net>
To: Daniel Colascione <dancol@google.com>,
Christian Brauner <christian@brauner.io>
Cc: Joel Fernandes <joel@joelfernandes.org>,
Jann Horn <jannh@google.com>, Oleg Nesterov <oleg@redhat.com>,
Florian Weimer <fweimer@redhat.com>,
kernel list <linux-kernel@vger.kernel.org>,
Andy Lutomirski <luto@amacapital.net>,
Steven Rostedt <rostedt@goodmis.org>,
Suren Baghdasaryan <surenb@google.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Alexey Dobriyan <adobriyan@gmail.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Andrei Vagin <avagin@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Arnd Bergmann <arnd@arndb.de>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Kees Cook <keescook@chromium.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
"open list:KERNEL SELFTEST FRAMEWORK"
<linux-kselftest@vger.kernel.org>, Michal Hocko <mhocko@suse.com>,
Nadav Amit <namit@vmware.com>, Serge Hallyn <serge@hallyn.com>,
Shuah Khan <shuah@kernel.org>,
Stephen Rothwell <sfr@canb.auug.org.au>,
Taehee Yoo <ap420073@gmail.com>, Tejun Heo <tj@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
kernel-team <kernel-team@android.com>,
Tycho Andersen <tycho@tycho.ws>
Subject: Re: [PATCH RFC 1/2] Add polling support to pidfd
Date: Wed, 24 Apr 2019 10:20:34 +0200 [thread overview]
Message-ID: <f631a11b-bdaa-1b07-dda5-028bf9efbd58@metux.net> (raw)
In-Reply-To: <CAKOZueuBTwyrLtpVQaoTAgjGSgeHY7392sKv5uAYdy4XKNHKHQ@mail.gmail.com>
On 19.04.19 23:21, Daniel Colascione wrote:
>> EPOLLIN on a pidfd could very well mean that data can be read via
>> a read() on the pidfd *other* than the exit status. The read could e.g.
>> give you a lean struct that indicates the type of state transition: NOTIFY_EXIT,
>> NOTIFY_EXEC, etc.. This way we are not bound to a specific poll event indicating
>> a specific state.
>> Though there's a case to be made that EPOLLHUP could indicate process exit
>> and EPOLLIN a state change + read().
>
> And do you imagine making read() destructive? Does that read() then
> reset the POLLIN state? You're essentially proposing that a pidfd
> provide an "event stream" interface, delivering notifications packets
> that indicate state changes like "process exited" or "process stopped"
> or "process execed". While this sort of interface is powerful and has
> some nice properties that tools like debuggers and daemon monitors
> might want to use, I think it's too complicated and error prone for
> the overwhelmingly common case of wanting to monitor process lifetime.
I don't think it's so complicated. read() + comparing a few bits
(eg. strncmp(), if the packets are strings) really isn't a big deal.
Actually, I proposed quite the same (before I read this mail).
> I like Linus' idea of just making waitid(2) (not waitpid(2), as I
> mistakenly mentioned earlier) on a pidfd act *exactly* like a
> waitid(2) on the corresponding process and making POLLIN just mean
> "waitid will succeed". It's a nice simple model that's easy to reason
> about and that makes it easy to port existing code to pidfds.
Okay, that's probably a good starting point. We could add more
sophisticated monitoring later.
--mtx
--
Enrico Weigelt, metux IT consult
Free software and Linux embedded engineering
info@metux.net -- +49-151-27565287
next prev parent reply other threads:[~2019-04-24 8:22 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-11 17:50 [PATCH RFC 1/2] Add polling support to pidfd Joel Fernandes (Google)
2019-04-11 17:50 ` [PATCH RFC 2/2] Add selftests for pidfd polling Joel Fernandes (Google)
2019-04-12 14:51 ` Tycho Andersen
2019-04-11 20:00 ` [PATCH RFC 1/2] Add polling support to pidfd Joel Fernandes
2019-04-11 20:02 ` Christian Brauner
2019-04-11 20:20 ` Joel Fernandes
2019-04-12 21:32 ` Andy Lutomirski
2019-04-13 0:09 ` Joel Fernandes
[not found] ` <CAKOZuetX4jMPDtDqAvGgSNo4BHf9BOnu79ufEiULfM5X5nDyyQ@mail.gmail.com>
2019-04-13 0:56 ` Daniel Colascione
2019-04-14 18:19 ` Linus Torvalds
2019-04-16 12:04 ` Oleg Nesterov
2019-04-16 12:43 ` Oleg Nesterov
2019-04-16 19:20 ` Joel Fernandes
2019-04-16 19:32 ` Joel Fernandes
2019-04-17 13:09 ` Oleg Nesterov
2019-04-18 17:23 ` Jann Horn
2019-04-18 17:26 ` Christian Brauner
2019-04-18 17:53 ` Daniel Colascione
2019-04-19 19:02 ` Joel Fernandes
2019-04-19 19:18 ` Christian Brauner
2019-04-19 19:22 ` Christian Brauner
2019-04-19 19:42 ` Christian Brauner
2019-04-19 19:49 ` Joel Fernandes
2019-04-19 20:01 ` Christian Brauner
2019-04-19 21:13 ` Joel Fernandes
2019-04-19 20:34 ` Daniel Colascione
2019-04-19 20:57 ` Christian Brauner
2019-04-19 21:20 ` Joel Fernandes
2019-04-19 21:24 ` Daniel Colascione
2019-04-19 21:45 ` Joel Fernandes
2019-04-19 22:08 ` Daniel Colascione
2019-04-19 22:17 ` Christian Brauner
2019-04-19 22:37 ` Daniel Colascione
2019-04-24 8:04 ` Enrico Weigelt, metux IT consult
2019-04-19 21:59 ` Christian Brauner
2019-04-20 11:51 ` Oleg Nesterov
2019-04-20 12:26 ` Oleg Nesterov
2019-04-20 12:35 ` Christian Brauner
2019-04-19 23:11 ` Linus Torvalds
2019-04-19 23:20 ` Christian Brauner
2019-04-19 23:32 ` Linus Torvalds
2019-04-19 23:36 ` Daniel Colascione
2019-04-20 0:46 ` Joel Fernandes
2019-04-19 21:21 ` Daniel Colascione
2019-04-19 21:48 ` Christian Brauner
2019-04-19 22:02 ` Christian Brauner
2019-04-19 22:46 ` Daniel Colascione
2019-04-19 23:12 ` Christian Brauner
2019-04-19 23:46 ` Daniel Colascione
2019-04-20 0:17 ` Christian Brauner
2019-04-24 9:05 ` Enrico Weigelt, metux IT consult
2019-04-24 9:03 ` Enrico Weigelt, metux IT consult
2019-04-19 22:35 ` Daniel Colascione
2019-04-19 23:02 ` Christian Brauner
2019-04-19 23:29 ` Daniel Colascione
2019-04-20 0:02 ` Christian Brauner
2019-04-24 9:17 ` Enrico Weigelt, metux IT consult
2019-04-24 9:11 ` Enrico Weigelt, metux IT consult
2019-04-24 8:56 ` Enrico Weigelt, metux IT consult
2019-04-24 8:20 ` Enrico Weigelt, metux IT consult [this message]
2019-04-19 15:43 ` Oleg Nesterov
2019-04-19 18:12 ` Joel Fernandes
2019-04-18 18:44 ` Jonathan Kowalski
2019-04-18 18:57 ` Daniel Colascione
2019-04-18 19:14 ` Linus Torvalds
2019-04-19 19:05 ` Joel Fernandes
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