From mboxrd@z Thu Jan  1 00:00:00 1970
From: erik quanstrom <quanstro@quanstro.net>
Date: Thu, 23 Aug 2012 11:48:05 -0400
To: 9fans@9fans.net
Message-ID: <8f993036a08798eb44ab78b5c8241885@brasstown.quanstro.net>
In-Reply-To: <2A9FAAF6-97E1-45A6-BF54-609130B99FA3@bitblocks.com>
References: <ddde182808bdb363b6ed3c1501cbea21@rei2.9hal>
	<f427e6fbd5322834343407f964454d92@kw.quanstro.net>
	<2A9FAAF6-97E1-45A6-BF54-609130B99FA3@bitblocks.com>
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Subject: Re: [9fans] devmnt crash, fix.
Topicbox-Message-UUID: aed94f8e-ead7-11e9-9d60-3106f5b1d025

>
> Indeed. One way to catch sleep() errors  is to change wakeup() to wake *everyone* up.

i was thinking on this and it occurred to me ....

to make the point by absurdity, consider this approximation
of sleep and wakeup without notes.

	void
	sleep(Rendez*, void (*)(void*), void*)
	{
	}

	void
	wakeup(Rendez*)
	{
	}

these have the property that you may wake without the condition
but you may not miss a wakeup.  it also doesn't matter if the condition
happens while sleep is executing.  and there is no hazard between
the two.  so i think this impemenation does satisfy the all
the requirements!

i didn't say it was efficient.  :-)

i think what cinap is thinking is, how could devmnt's particular
use of sleep/wakeup with this particular implementation of sleep/wakeup
evade handling spurious wakeups.  if that's what the thought is,
i would resist it.  it may be that someone thinks of a very efficient
way of re-implementing sleep/wakeup that may have slightly different
properties.  as long as the client and sleep/wakeup play by the rules,
this should not be a problem.  (it's possible to do plan 9-style sleep
wakeup within, say, the windows kernel.)

- erik