On Mon, Feb 1, 2021, 7:22 PM Greg A. Woods wrote: > At Sun, 31 Jan 2021 09:27:10 +1100 (EST), Dave Horsfall > 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 > > Kelowna, BC +1 250 762-7675 RoboHack > Planix, Inc. Avoncote Farms >