From: Warner Losh <imp@bsdimp.com>
To: The Unix Heritage Society mailing list <tuhs@tuhs.org>
Subject: Re: [TUHS] reboot(2) system call
Date: Mon, 1 Feb 2021 19:30:47 -0700 [thread overview]
Message-ID: <CANCZdfqnAtRmLQCe2=WZ22S+9vLn81aD1zC-zOb6cchJ2TzrrA@mail.gmail.com> (raw)
In-Reply-To: <m1l6lJK-0036x9C@more.local>
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On Mon, Feb 1, 2021, 7:22 PM Greg A. Woods <woods@robohack.ca> wrote:
> At Sun, 31 Jan 2021 09:27:10 +1100 (EST), Dave Horsfall <dave@horsfall.org>
> wrote:
> Subject: Re: [TUHS] reboot(2) system call
> >
> > On Tue, 26 Jan 2021, Greg A. Woods wrote:
> >
> > > The lore I was told at the time was that you alwasy ran three and
> > > that it didn't matter if they were all on the same line with
> > > semicolons or not because of the very fact that the second one would
> > > block.
> >
> > What I was taught was:
> >
> > % sync
> > % sync
> > % sync
> >
> > and never:
> >
> > % sync; sync; sync
> >
> > The theory was that by waiting for the shell prompt each time, it gave
> > the buffer pool enough time to be flushed.
>
> If waiting was the true reason, then any sane person would have put a
> sleep in there instead so as to avoid any variance in typing (and
> terminal) speed.
>
> On at least a large number of old systems I've used either the first or
> the second invocation did block and not return if there were still any
> dirty blocks it made the sync() call. It was trivial to see that the
> system was busy writing while one waited for the shell prompt to
> re-appear if one could see the disk activity lights (or hear them) from
> the console, as was usually easy to do on desktop systems.
>
> Since many of those old systems I used were Xenix of one flavour or
> another, perhaps it was only those that waited for sync I/O to complete.
>
Would be nice to know which one so I can go check. I've not seen leaked
xenix code though, so it may be possible.
Warner
--
> Greg A. Woods <gwoods@acm.org>
>
> Kelowna, BC +1 250 762-7675 RoboHack <woods@robohack.ca>
> Planix, Inc. <woods@planix.com> Avoncote Farms <woods@avoncote.ca>
>
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next prev parent reply other threads:[~2021-02-02 2:31 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-27 18:57 Warner Losh
2020-07-28 0:36 ` Clem Cole
2020-07-28 4:06 ` Dave Horsfall
2020-07-28 16:35 ` Win Treese
2020-07-28 13:11 ` Jaap Akkerhuis
2021-01-27 6:01 ` Greg A. Woods
2021-01-30 22:27 ` Dave Horsfall
2021-01-30 22:31 ` Larry McVoy
2021-01-30 22:37 ` Warner Losh
2021-02-02 2:20 ` Greg A. Woods
2021-02-02 2:30 ` Warner Losh [this message]
2021-02-02 20:30 ` Greg A. Woods
2021-02-02 3:35 ` Dave Horsfall
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