From: Christian Brauner <christian.brauner@ubuntu.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: "Cyrill Gorcunov" <gorcunov@gmail.com>,
"y2038 Mailman List" <y2038@lists.linaro.org>,
"Richard Henderson" <rth@twiddle.net>,
"Ivan Kokshaysky" <ink@jurassic.park.msu.ru>,
"Matt Turner" <mattst88@gmail.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Deepa Dinamani" <deepa.kernel@gmail.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Will Deacon" <will@kernel.org>,
"Michal Koutný" <mkoutny@suse.com>,
"Catalin Marinas" <catalin.marinas@arm.com>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
alpha <linux-alpha@vger.kernel.org>,
fweimer@redhat.com, libc-alpha@sourceware.org
Subject: Re: [PATCH 11/23] y2038: rusage: use __kernel_old_timeval
Date: Thu, 14 Nov 2019 11:23:47 +0100 [thread overview]
Message-ID: <20191114102346.bjwsz2iup7pg7mgd@wittgenstein> (raw)
In-Reply-To: <CAK8P3a2JtyfFifSWNd2MA-J=6-NdgPd4eNva+u193bzQTX6Qig@mail.gmail.com>
[+Cc Florian, libc-alpha]
On Thu, Nov 14, 2019 at 11:18:15AM +0100, Arnd Bergmann wrote:
> On Thu, Nov 14, 2019 at 1:38 AM Christian Brauner
> <christian.brauner@ubuntu.com> wrote:
> > On Wed, Nov 13, 2019 at 11:02:12AM +0100, Arnd Bergmann wrote:
> > > On Tue, Nov 12, 2019 at 10:09 PM Cyrill Gorcunov <gorcunov@gmail.com> wrote:
> > > >
> > > > On Fri, Nov 08, 2019 at 10:12:10PM +0100, Arnd Bergmann wrote:
> > >
> > > > > ---
> > > > > Question: should we also rename 'struct rusage' into 'struct __kernel_rusage'
> > > > > here, to make them completely unambiguous?
> > > >
> > > > The patch looks ok to me. I must confess I looked into rusage long ago
> > > > so __kernel_timespec type used in uapi made me nervious at first,
> > > > but then i found that we've this type defined in time_types.h uapi
> > > > so userspace should be safe. I also like the idea of __kernel_rusage
> > > > but definitely on top of the series.
> > >
> > > There are clearly too many time types at the moment, but I'm in the
> > > process of throwing out the ones we no longer need now.
> > >
> > > I do have a number patches implementing other variants for the syscall,
> > > and I suppose that if we end up adding __kernel_rusage, that would
> > > have to go with a set of syscalls using 64-bit seconds/nanoseconds
> > > rather than the old 32/64 microseconds. I don't know what other
> > > changes remain that anyone would want from sys_waitid() now that
> > > it does support pidfd.
> > >
> > > If there is still a need for a new waitid() replacement, that should take
> > > that new __kernel_rusage I think, but until then I hope we are fine
> > > with today's getrusage+waitid based on the current struct rusage.
> >
> > Note, that glibc does _not_ expose the rusage argument, i.e. most of
> > userspace is unaware that waitid() does allow you to get rusage
> > information. So users first need to know that waitid() has an rusage
> > argument and then need to call the waitid() syscall directly.
>
> On architectures that don't have a wait4 syscall (riscv32 for now),
> glibc uses waitid to implement wait4 and wait3.
Yes, and there's an ongoing discussion to implement wait4() on all
arches through waitid(), I think. I haven't followed it too closely.
>
> > > BSD has wait6() to return separate rusage structures for 'self' and
> > > 'children', but I could not find any application (using the freebsd
> > > sources and debian code search) that actually uses that information,
> > > so there might not be any demand for that.
> >
> > Speaking specifically for Linux now, I think that rusage does not
> > actually expose the information most relevant users are interested in.
> > On Linux nowadays it is _way_ more interesting to retrieve stats
> > relative to the cgroup the task lived in etc.
> > Doing a git grep -i rusage in the systemd source code shows that rusage
> > is used _nowhere_. And I consider an init system to be the most likely
> > candidate to be interested in rusage.
>
> I looked at a couple of implementations of time(1), this is one example
> that sometimes uses wait3(), though other implementations just call
> getrusage() in the parent process before the fork/exec. None of them
> actually seem to report better than millisecond resolution, so there is
> not a strict reason to do a timespec replacement for these.
Right, though I have to say that for the sake of consistency I'd much
rather have a replacement. We're doing all this work right now so we
might as well. But I get the point.
Christian
next prev parent reply other threads:[~2019-11-14 10:23 UTC|newest]
Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-08 21:02 [PATCH 00/23] y2038 cleanups Arnd Bergmann
2019-11-08 21:07 ` [PATCH 01/23] y2038: remove CONFIG_64BIT_TIME Arnd Bergmann
2019-11-20 22:28 ` [Y2038] " Ben Hutchings
2019-11-20 22:58 ` Dmitry Safonov
2019-11-08 21:07 ` [PATCH 02/23] y2038: add __kernel_old_timespec and __kernel_old_time_t Arnd Bergmann
2019-11-09 19:02 ` Deepa Dinamani
2019-11-20 22:30 ` [Y2038] " Ben Hutchings
2019-11-21 14:17 ` Arnd Bergmann
2019-11-08 21:07 ` [PATCH 03/23] y2038: vdso: change timeval to __kernel_old_timeval Arnd Bergmann
2019-11-13 21:56 ` Thomas Gleixner
2019-11-08 21:07 ` [PATCH 04/23] y2038: vdso: change timespec to __kernel_old_timespec Arnd Bergmann
2019-11-08 21:07 ` [PATCH 05/23] y2038: vdso: change time_t to __kernel_old_time_t Arnd Bergmann
2019-11-13 21:57 ` Thomas Gleixner
2019-11-08 21:07 ` [PATCH 06/23] y2038: vdso: nds32: open-code timespec_add_ns() Arnd Bergmann
2019-11-08 21:07 ` [PATCH 07/23] y2038: vdso: powerpc: avoid timespec references Arnd Bergmann
2019-11-20 22:43 ` [Y2038] " Ben Hutchings
2019-11-21 14:23 ` Arnd Bergmann
2019-11-21 16:25 ` Christophe Leroy
2019-11-27 11:03 ` Arnd Bergmann
2019-12-02 12:55 ` Christophe Leroy
2019-12-02 14:03 ` Arnd Bergmann
2019-11-08 21:07 ` [PATCH 08/23] y2038: ipc: remove __kernel_time_t reference from headers Arnd Bergmann
2019-11-20 22:49 ` [Y2038] " Ben Hutchings
2019-11-21 14:28 ` Arnd Bergmann
2019-11-08 21:07 ` [PATCH 09/23] y2038: stat: avoid 'time_t' in 'struct stat' Arnd Bergmann
2019-11-08 21:12 ` [PATCH 10/23] y2038: uapi: change __kernel_time_t to __kernel_old_time_t Arnd Bergmann
2019-11-09 19:03 ` Deepa Dinamani
2019-11-11 12:38 ` Christian Brauner
2019-11-08 21:12 ` [PATCH 11/23] y2038: rusage: use __kernel_old_timeval Arnd Bergmann
2019-11-12 21:09 ` Cyrill Gorcunov
2019-11-13 10:02 ` Arnd Bergmann
2019-11-13 17:22 ` Cyrill Gorcunov
2019-11-14 0:38 ` Christian Brauner
2019-11-14 10:18 ` Arnd Bergmann
2019-11-14 10:23 ` Christian Brauner [this message]
2019-11-08 21:12 ` [PATCH 12/23] y2038: syscalls: change remaining timeval to __kernel_old_timeval Arnd Bergmann
2019-11-11 12:44 ` Christian Brauner
2019-11-13 22:39 ` Rafael J. Wysocki
2019-11-08 21:12 ` [PATCH 13/23] y2038: socket: remove timespec reference in timestamping Arnd Bergmann
2019-11-09 19:03 ` Deepa Dinamani
2019-11-11 20:24 ` Arnd Bergmann
2019-11-08 21:12 ` [PATCH 14/23] y2038: make ns_to_compat_timeval use __kernel_old_timeval Arnd Bergmann
2019-11-08 21:12 ` [PATCH 15/23] y2038: elfcore: Use __kernel_old_timeval for process times Arnd Bergmann
2019-11-08 21:12 ` [PATCH 16/23] y2038: timerfd: Use timespec64 internally Arnd Bergmann
2019-11-13 21:49 ` Thomas Gleixner
2019-11-08 21:12 ` [PATCH 17/23] y2038: time: avoid timespec usage in settimeofday() Arnd Bergmann
2019-11-13 21:53 ` Thomas Gleixner
2019-11-14 11:06 ` Arnd Bergmann
2019-11-14 14:04 ` Thomas Gleixner
2019-11-14 14:35 ` Arnd Bergmann
2019-11-14 23:01 ` Abel Vesa
2019-11-15 7:58 ` Arnd Bergmann
2019-11-15 10:27 ` Rasmus Villemoes
2019-11-15 13:50 ` Arnd Bergmann
2019-11-08 21:12 ` [PATCH 18/23] y2038: itimer: compat handling to itimer.c Arnd Bergmann
2019-11-13 21:54 ` Thomas Gleixner
2019-11-08 21:12 ` [PATCH 19/23] y2038: use compat_{get,set}_itimer on alpha Arnd Bergmann
2019-12-02 13:13 ` Guenter Roeck
2019-11-08 21:12 ` [PATCH 20/23] y2038: move itimer reset into itimer.c Arnd Bergmann
2019-11-09 13:43 ` Ondrej Mosnacek
2019-11-09 21:02 ` Arnd Bergmann
2019-11-09 23:07 ` Ondrej Mosnacek
2019-11-11 10:57 ` Arnd Bergmann
2019-11-14 8:51 ` Ondrej Mosnacek
2019-11-14 10:51 ` Thomas Gleixner
2019-11-13 22:03 ` Thomas Gleixner
2019-11-08 21:12 ` [PATCH 21/23] y2038: itimer: change implementation to timespec64 Arnd Bergmann
2019-11-13 22:28 ` Thomas Gleixner
2019-11-14 2:06 ` Steven Rostedt
2019-11-14 10:48 ` Thomas Gleixner
2019-11-14 10:52 ` Arnd Bergmann
2019-11-14 10:51 ` Arnd Bergmann
2019-11-14 10:57 ` Thomas Gleixner
2019-11-21 16:52 ` [Y2038] " Ben Hutchings
2019-11-25 20:26 ` Arnd Bergmann
2019-11-08 21:12 ` [PATCH 22/23] [RFC] y2038: itimer: use ktime_t internally Arnd Bergmann
2019-11-13 22:30 ` Thomas Gleixner
2019-11-08 21:12 ` [PATCH 23/23] y2038: allow disabling time32 system calls Arnd Bergmann
2019-11-11 12:31 ` Christian Brauner
2019-11-13 21:40 ` [PATCH 00/23] y2038 cleanups Arnd Bergmann
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