From: Joel Fernandes <joel@joelfernandes.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Daniel Colascione <dancol@google.com>,
Jonathan Kowalski <bl0pbl33p@gmail.com>,
Oleg Nesterov <oleg@redhat.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Andy Lutomirski <luto@amacapital.net>,
Steven Rostedt <rostedt@goodmis.org>,
Christian Brauner <christian@brauner.io>,
Jann Horn <jannh@google.com>,
Suren Baghdasaryan <surenb@google.com>,
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 FS Devel <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>,
Android Kernel Team <kernel-team@android.com>,
Tycho Andersen <tycho@tycho.ws>
Subject: Re: [PATCH RFC 1/2] Add polling support to pidfd
Date: Fri, 19 Apr 2019 15:05:38 -0400 [thread overview]
Message-ID: <20190419190538.GC251571@google.com> (raw)
In-Reply-To: <CAHk-=wi79KTxCYZgMZNapULR-ratPiZVt+fgh=DhgtYR_gYPAA@mail.gmail.com>
On Thu, Apr 18, 2019 at 12:14:58PM -0700, Linus Torvalds wrote:
> On Thu, Apr 18, 2019 at 11:58 AM Daniel Colascione <dancol@google.com> wrote:
> >
> > On Thu, Apr 18, 2019 at 11:44 AM Jonathan Kowalski <bl0pbl33p@gmail.com> wrote:
> > >
> > > Would using something other than POLLIN be an option (maybe POLLPRI)?
> > > The convention is to use it to indicate readability on the descriptor,
> > > and also possibly POLLHUP instead of POLLERR (the latter is less of a
> > > problem, but FreeBSD also does the same, so it'd help with some
> > > consistency for libraries wanting to use this, which aren't interested
> > > in other sub states).
> >
> > Existing event loop libraries generally support checking only for
> > readability and writability. Not setting POLLIN would make these FDs
> > more difficult to use with existing event loop libraries. What
> > advantage would compensate for this difficulty?
>
> Right.
>
> Usually you'd set POLLIN in _addition_ to any other more specialized poll flag.
>
> For example, when a socket has shut down the read side, we do
>
> if (sk->sk_shutdown & RCV_SHUTDOWN)
> mask |= EPOLLRDHUP | EPOLLIN | EPOLLRDNORM;
>
> because while it's true that EPOLLRDHUP is the most _specific_ poll
> bit, it's _also_ true that a read shutdown means that the read() will
> return immediately.
>
> So generally a HUP condition should mean that POLLIN and POLLOUT also
> get set. Not because there's any actual _data_ to be read, but simply
> because the read will not block.
Sounds great and I agree with Linus and Daniel. So I am guessing you are Ok
with the current set of flags proposed this patch, so I will keep them intact
in future patch postings. But please let me know if you want me to change
something about the flags.
thanks!
- Joel
WARNING: multiple messages have this Message-ID (diff)
From: joel at joelfernandes.org (Joel Fernandes)
Subject: [PATCH RFC 1/2] Add polling support to pidfd
Date: Fri, 19 Apr 2019 15:05:38 -0400 [thread overview]
Message-ID: <20190419190538.GC251571@google.com> (raw)
In-Reply-To: <CAHk-=wi79KTxCYZgMZNapULR-ratPiZVt+fgh=DhgtYR_gYPAA@mail.gmail.com>
On Thu, Apr 18, 2019 at 12:14:58PM -0700, Linus Torvalds wrote:
> On Thu, Apr 18, 2019 at 11:58 AM Daniel Colascione <dancol at google.com> wrote:
> >
> > On Thu, Apr 18, 2019 at 11:44 AM Jonathan Kowalski <bl0pbl33p at gmail.com> wrote:
> > >
> > > Would using something other than POLLIN be an option (maybe POLLPRI)?
> > > The convention is to use it to indicate readability on the descriptor,
> > > and also possibly POLLHUP instead of POLLERR (the latter is less of a
> > > problem, but FreeBSD also does the same, so it'd help with some
> > > consistency for libraries wanting to use this, which aren't interested
> > > in other sub states).
> >
> > Existing event loop libraries generally support checking only for
> > readability and writability. Not setting POLLIN would make these FDs
> > more difficult to use with existing event loop libraries. What
> > advantage would compensate for this difficulty?
>
> Right.
>
> Usually you'd set POLLIN in _addition_ to any other more specialized poll flag.
>
> For example, when a socket has shut down the read side, we do
>
> if (sk->sk_shutdown & RCV_SHUTDOWN)
> mask |= EPOLLRDHUP | EPOLLIN | EPOLLRDNORM;
>
> because while it's true that EPOLLRDHUP is the most _specific_ poll
> bit, it's _also_ true that a read shutdown means that the read() will
> return immediately.
>
> So generally a HUP condition should mean that POLLIN and POLLOUT also
> get set. Not because there's any actual _data_ to be read, but simply
> because the read will not block.
Sounds great and I agree with Linus and Daniel. So I am guessing you are Ok
with the current set of flags proposed this patch, so I will keep them intact
in future patch postings. But please let me know if you want me to change
something about the flags.
thanks!
- Joel
WARNING: multiple messages have this Message-ID (diff)
From: joel@joelfernandes.org (Joel Fernandes)
Subject: [PATCH RFC 1/2] Add polling support to pidfd
Date: Fri, 19 Apr 2019 15:05:38 -0400 [thread overview]
Message-ID: <20190419190538.GC251571@google.com> (raw)
Message-ID: <20190419190538.p-Uth0cDmqvvaz0rDkufqvO27Q5qf14SUXR3TWOBT3E@z> (raw)
In-Reply-To: <CAHk-=wi79KTxCYZgMZNapULR-ratPiZVt+fgh=DhgtYR_gYPAA@mail.gmail.com>
On Thu, Apr 18, 2019@12:14:58PM -0700, Linus Torvalds wrote:
> On Thu, Apr 18, 2019@11:58 AM Daniel Colascione <dancol@google.com> wrote:
> >
> > On Thu, Apr 18, 2019@11:44 AM Jonathan Kowalski <bl0pbl33p@gmail.com> wrote:
> > >
> > > Would using something other than POLLIN be an option (maybe POLLPRI)?
> > > The convention is to use it to indicate readability on the descriptor,
> > > and also possibly POLLHUP instead of POLLERR (the latter is less of a
> > > problem, but FreeBSD also does the same, so it'd help with some
> > > consistency for libraries wanting to use this, which aren't interested
> > > in other sub states).
> >
> > Existing event loop libraries generally support checking only for
> > readability and writability. Not setting POLLIN would make these FDs
> > more difficult to use with existing event loop libraries. What
> > advantage would compensate for this difficulty?
>
> Right.
>
> Usually you'd set POLLIN in _addition_ to any other more specialized poll flag.
>
> For example, when a socket has shut down the read side, we do
>
> if (sk->sk_shutdown & RCV_SHUTDOWN)
> mask |= EPOLLRDHUP | EPOLLIN | EPOLLRDNORM;
>
> because while it's true that EPOLLRDHUP is the most _specific_ poll
> bit, it's _also_ true that a read shutdown means that the read() will
> return immediately.
>
> So generally a HUP condition should mean that POLLIN and POLLOUT also
> get set. Not because there's any actual _data_ to be read, but simply
> because the read will not block.
Sounds great and I agree with Linus and Daniel. So I am guessing you are Ok
with the current set of flags proposed this patch, so I will keep them intact
in future patch postings. But please let me know if you want me to change
something about the flags.
thanks!
- Joel
next prev parent reply other threads:[~2019-04-19 19:05 UTC|newest]
Thread overview: 198+ 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 ` Joel Fernandes (Google)
2019-04-11 17:50 ` joel
2019-04-11 17:50 ` [PATCH RFC 2/2] Add selftests for pidfd polling Joel Fernandes (Google)
2019-04-11 17:50 ` Joel Fernandes (Google)
2019-04-11 17:50 ` joel
2019-04-12 14:51 ` Tycho Andersen
2019-04-12 14:51 ` Tycho Andersen
2019-04-12 14:51 ` tycho
2019-04-11 20:00 ` [PATCH RFC 1/2] Add polling support to pidfd Joel Fernandes
2019-04-11 20:00 ` Joel Fernandes
2019-04-11 20:00 ` joel
2019-04-11 20:02 ` Christian Brauner
2019-04-11 20:02 ` Christian Brauner
2019-04-11 20:02 ` christian
2019-04-11 20:20 ` Joel Fernandes
2019-04-11 20:20 ` Joel Fernandes
2019-04-11 20:20 ` joel
2019-04-12 21:32 ` Andy Lutomirski
2019-04-12 21:32 ` Andy Lutomirski
2019-04-12 21:32 ` luto
2019-04-13 0:09 ` Joel Fernandes
2019-04-13 0:09 ` Joel Fernandes
2019-04-13 0:09 ` joel
[not found] ` <CAKOZuetX4jMPDtDqAvGgSNo4BHf9BOnu79ufEiULfM5X5nDyyQ@mail.gmail.com>
2019-04-13 0:56 ` Daniel Colascione
2019-04-13 0:56 ` Daniel Colascione
2019-04-13 0:56 ` dancol
2019-04-14 18:19 ` Linus Torvalds
2019-04-14 18:19 ` Linus Torvalds
2019-04-14 18:19 ` torvalds
2019-04-16 12:04 ` Oleg Nesterov
2019-04-16 12:04 ` Oleg Nesterov
2019-04-16 12:04 ` oleg
2019-04-16 12:43 ` Oleg Nesterov
2019-04-16 12:43 ` Oleg Nesterov
2019-04-16 12:43 ` oleg
2019-04-16 19:20 ` Joel Fernandes
2019-04-16 19:20 ` Joel Fernandes
2019-04-16 19:20 ` joel
2019-04-16 19:32 ` Joel Fernandes
2019-04-16 19:32 ` Joel Fernandes
2019-04-16 19:32 ` joel
2019-04-17 13:09 ` Oleg Nesterov
2019-04-17 13:09 ` Oleg Nesterov
2019-04-17 13:09 ` oleg
2019-04-18 17:23 ` Jann Horn
2019-04-18 17:23 ` Jann Horn
2019-04-18 17:23 ` jannh
2019-04-18 17:26 ` Christian Brauner
2019-04-18 17:26 ` Christian Brauner
2019-04-18 17:26 ` christian
2019-04-18 17:53 ` Daniel Colascione
2019-04-18 17:53 ` Daniel Colascione
2019-04-18 17:53 ` dancol
2019-04-19 19:02 ` Joel Fernandes
2019-04-19 19:02 ` Joel Fernandes
2019-04-19 19:02 ` joel
2019-04-19 19:18 ` Christian Brauner
2019-04-19 19:18 ` Christian Brauner
2019-04-19 19:18 ` christian
2019-04-19 19:22 ` Christian Brauner
2019-04-19 19:22 ` Christian Brauner
2019-04-19 19:22 ` christian
2019-04-19 19:42 ` Christian Brauner
2019-04-19 19:42 ` Christian Brauner
2019-04-19 19:42 ` christian
2019-04-19 19:49 ` Joel Fernandes
2019-04-19 19:49 ` Joel Fernandes
2019-04-19 19:49 ` joel
2019-04-19 20:01 ` Christian Brauner
2019-04-19 20:01 ` Christian Brauner
2019-04-19 20:01 ` christian
2019-04-19 21:13 ` Joel Fernandes
2019-04-19 21:13 ` Joel Fernandes
2019-04-19 21:13 ` joel
2019-04-19 20:34 ` Daniel Colascione
2019-04-19 20:34 ` Daniel Colascione
2019-04-19 20:34 ` dancol
2019-04-19 20:57 ` Christian Brauner
2019-04-19 20:57 ` Christian Brauner
2019-04-19 20:57 ` christian
2019-04-19 21:20 ` Joel Fernandes
2019-04-19 21:20 ` Joel Fernandes
2019-04-19 21:20 ` joel
2019-04-19 21:24 ` Daniel Colascione
2019-04-19 21:24 ` Daniel Colascione
2019-04-19 21:24 ` dancol
2019-04-19 21:45 ` Joel Fernandes
2019-04-19 21:45 ` Joel Fernandes
2019-04-19 21:45 ` joel
2019-04-19 22:08 ` Daniel Colascione
2019-04-19 22:08 ` Daniel Colascione
2019-04-19 22:08 ` dancol
2019-04-19 22:17 ` Christian Brauner
2019-04-19 22:17 ` Christian Brauner
2019-04-19 22:17 ` christian
2019-04-19 22:37 ` Daniel Colascione
2019-04-19 22:37 ` Daniel Colascione
2019-04-19 22:37 ` dancol
2019-04-24 8:04 ` Enrico Weigelt, metux IT consult
2019-04-24 8:04 ` Enrico Weigelt, metux IT consult
2019-04-24 8:04 ` lkml
2019-04-19 21:59 ` Christian Brauner
2019-04-19 21:59 ` Christian Brauner
2019-04-19 21:59 ` christian
2019-04-20 11:51 ` Oleg Nesterov
2019-04-20 11:51 ` Oleg Nesterov
2019-04-20 11:51 ` oleg
2019-04-20 12:26 ` Oleg Nesterov
2019-04-20 12:26 ` Oleg Nesterov
2019-04-20 12:26 ` oleg
2019-04-20 12:35 ` Christian Brauner
2019-04-20 12:35 ` Christian Brauner
2019-04-20 12:35 ` christian
2019-04-19 23:11 ` Linus Torvalds
2019-04-19 23:11 ` Linus Torvalds
2019-04-19 23:11 ` torvalds
2019-04-19 23:20 ` Christian Brauner
2019-04-19 23:20 ` Christian Brauner
2019-04-19 23:20 ` christian
2019-04-19 23:32 ` Linus Torvalds
2019-04-19 23:32 ` Linus Torvalds
2019-04-19 23:32 ` torvalds
2019-04-19 23:36 ` Daniel Colascione
2019-04-19 23:36 ` Daniel Colascione
2019-04-19 23:36 ` dancol
2019-04-20 0:46 ` Joel Fernandes
2019-04-20 0:46 ` Joel Fernandes
2019-04-20 0:46 ` joel
2019-04-19 21:21 ` Daniel Colascione
2019-04-19 21:21 ` Daniel Colascione
2019-04-19 21:21 ` dancol
2019-04-19 21:48 ` Christian Brauner
2019-04-19 21:48 ` Christian Brauner
2019-04-19 21:48 ` christian
2019-04-19 22:02 ` Christian Brauner
2019-04-19 22:02 ` Christian Brauner
2019-04-19 22:02 ` christian
2019-04-19 22:46 ` Daniel Colascione
2019-04-19 22:46 ` Daniel Colascione
2019-04-19 22:46 ` dancol
2019-04-19 23:12 ` Christian Brauner
2019-04-19 23:12 ` Christian Brauner
2019-04-19 23:12 ` christian
2019-04-19 23:46 ` Daniel Colascione
2019-04-19 23:46 ` Daniel Colascione
2019-04-19 23:46 ` dancol
2019-04-20 0:17 ` Christian Brauner
2019-04-20 0:17 ` Christian Brauner
2019-04-20 0:17 ` christian
2019-04-24 9:05 ` Enrico Weigelt, metux IT consult
2019-04-24 9:05 ` Enrico Weigelt, metux IT consult
2019-04-24 9:05 ` lkml
2019-04-24 9:03 ` Enrico Weigelt, metux IT consult
2019-04-24 9:03 ` Enrico Weigelt, metux IT consult
2019-04-24 9:03 ` lkml
2019-04-19 22:35 ` Daniel Colascione
2019-04-19 22:35 ` Daniel Colascione
2019-04-19 22:35 ` dancol
2019-04-19 23:02 ` Christian Brauner
2019-04-19 23:02 ` Christian Brauner
2019-04-19 23:02 ` christian
2019-04-19 23:29 ` Daniel Colascione
2019-04-19 23:29 ` Daniel Colascione
2019-04-19 23:29 ` dancol
2019-04-20 0:02 ` Christian Brauner
2019-04-20 0:02 ` Christian Brauner
2019-04-20 0:02 ` christian
2019-04-24 9:17 ` Enrico Weigelt, metux IT consult
2019-04-24 9:17 ` Enrico Weigelt, metux IT consult
2019-04-24 9:17 ` lkml
2019-04-24 9:11 ` Enrico Weigelt, metux IT consult
2019-04-24 9:11 ` Enrico Weigelt, metux IT consult
2019-04-24 9:11 ` lkml
2019-04-24 8:56 ` Enrico Weigelt, metux IT consult
2019-04-24 8:56 ` Enrico Weigelt, metux IT consult
2019-04-24 8:56 ` lkml
2019-04-24 8:20 ` Enrico Weigelt, metux IT consult
2019-04-24 8:20 ` Enrico Weigelt, metux IT consult
2019-04-24 8:20 ` lkml
2019-04-19 15:43 ` Oleg Nesterov
2019-04-19 15:43 ` Oleg Nesterov
2019-04-19 15:43 ` oleg
2019-04-19 18:12 ` Joel Fernandes
2019-04-19 18:12 ` Joel Fernandes
2019-04-19 18:12 ` joel
2019-04-18 18:44 ` Jonathan Kowalski
2019-04-18 18:44 ` Jonathan Kowalski
2019-04-18 18:44 ` bl0pbl33p
2019-04-18 18:57 ` Daniel Colascione
2019-04-18 18:57 ` Daniel Colascione
2019-04-18 18:57 ` dancol
2019-04-18 19:14 ` Linus Torvalds
2019-04-18 19:14 ` Linus Torvalds
2019-04-18 19:14 ` torvalds
2019-04-19 19:05 ` Joel Fernandes [this message]
2019-04-19 19:05 ` Joel Fernandes
2019-04-19 19:05 ` joel
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