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Re: [RFC v3 03/23] sysdeps/wait: Use waitid if avaliable
- From: Arnd Bergmann <arnd at arndb dot de>
- To: Rich Felker <dalias at libc dot org>
- Cc: Alistair Francis <alistair23 at gmail dot com>, Christian Brauner <christian at brauner dot io>, "Eric W. Biederman" <ebiederm at xmission dot com>, Linus Torvalds <torvalds at linux-foundation dot org>, Alistair Francis <alistair dot francis at wdc dot com>, GNU C Library <libc-alpha at sourceware dot org>, Adhemerval Zanella <adhemerval dot zanella at linaro dot org>, Florian Weimer <fweimer at redhat dot com>, Palmer Dabbelt <palmer at sifive dot com>, macro at wdc dot com, Zong Li <zongbox at gmail dot com>, Andrew Morton <akpm at linux-foundation dot org>, Al Viro <viro at zeniv dot linux dot org dot uk>, "H. Peter Anvin" <hpa at zytor dot com>
- Date: Thu, 25 Jul 2019 15:15:35 +0200
- Subject: Re: [RFC v3 03/23] sysdeps/wait: Use waitid if avaliable
- References: <CAK8P3a3wgavtarKxSYJGL0ME9KRZ8UsUAZw+Y5J8WpG1GQfirstname.lastname@example.org> <email@example.com> <CAHk-=wjtGaJFceL+YB6=mTxQCvyNvBTavqgGTm-d5FA9xLQ0Cw@mail.gmail.com> <firstname.lastname@example.org> <20190721232336.GA30851@brightrain.aerifal.cx> <email@example.com> <CAK8P3a0jOO8dDK+w0N_RvgUHiW7=i_ak9AyFvH61wqUusL3Drw@mail.gmail.com> <firstname.lastname@example.org> <CAK8P3a26KBRvJHyWkK0J8FGXQn4jHL2QG10oBGSLidG95xQxrw@mail.gmail.com> <CAKmqyKOXJxJq5-ktLc=oY7ooNj6-X9PotHNM=-xG95iPCAAmjQ@mail.gmail.com> <20190725044009.GJ1506@brightrain.aerifal.cx>
On Thu, Jul 25, 2019 at 6:40 AM Rich Felker <email@example.com> wrote:
> On Wed, Jul 24, 2019 at 05:04:53PM -0700, Alistair Francis wrote:
> > On Tue, Jul 23, 2019 at 1:45 AM Arnd Bergmann <firstname.lastname@example.org> wrote:
> > >
> > > Sounds good to me, the debate over what rusage to use should not hold
> > > up the review of the rest of that syscall.
> > I'm unclear what the final decision is here. What is the solution are
> > we going to have wait4() or add P_PROCESS_PGID to waitid()?
> > As well as that what is the solution to current implementations? If we
> > add wait4() then there isn't an issue (and I can drop this patch) but
> > if we add P_PROCESS_PGID then we will need a way to handle kernels
> > with waitid() but no P_PROCESS_PGID. Although my new plan is to only
> > use the waitid syscall if we don't have waitpid or wait4 so it seems
> > like this will only affect RV32 for the time being.
> I would really like some indication which solution will be taken,
> since it impacts choices that will need to be made in musl very soon.
> My favorite outcome would be bringing back wait4 for rv32 (and
> no-time32 archs in general) *and* adding P_PROCESS_PGID. In the short
> term, just using wait4 would be the simplest and cleanest for us (same
> as all other archs, no extra case to deal with), but in the long term
> there may be value in having rusage that can represent more than 68
> cpu-years spent by a process (seems plausible with large numbers of
Based on the feedback from Linus and Eric, the most likely outcome
at the moment seems to be an extension of waitid() to allow
P_PGID with id=0 like BSD does, and not bring back wait4() or
So far, I don't think anyone has proposed an actual kernel patch.
I was hoping that Eric would do it, but I could also send it if he's