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From: Roman Perepelitsa <roman.perepelitsa@gmail.com>
Date: Sat, 27 Jun 2020 09:27:08 +0200
Message-ID: <CAN=4vMpFpaQg03JbY_B3ktXAEmiUhXH4crdwyc1Ups8Cf=nf8A@mail.gmail.com>
Subject: Re: [BUG] zsystem:34: flock: invalid timeout value: '0'
To: Cedric Ware <cedric.ware__bml@normalesup.org>
Cc: Bart Schaefer <schaefer@brasslantern.com>, Daniel Shahaf <d.s@daniel.shahaf.name>, 
	Sebastian Gniazdowski <sgniazdowski@gmail.com>, Zsh hackers list <zsh-workers@zsh.org>
Content-Type: text/plain; charset="UTF-8"

On Sat, Jun 27, 2020 at 9:14 AM Cedric Ware
<cedric.ware__bml@normalesup.org> wrote:
>
> I didn't want to allow specifying a timeout below 1 microsecond,
> because that's the granularity of zsleep().  One could still allow it
> but silently treat it as 0.

Timeout strictly between 0 and 1 microsecond is not much different
from timeout between 1 and 2 microseconds. You can either round up or
down in both cases. Rounding up is the right thing to do for sleeps
and timeouts because it allows you to provide a guarantee.

For sleep (pseudo code):

    time start = now();
    if (sleep(duration) != INTERRUPTED)
      assert(now - start() >= duration);

For anything with a timeout (pseudo code):

    time start = now();
    if (do_with_timeout(duration) == TIMEDOUT)
      assert(now - start() >= duration);

If you round down, there is no non-trivial assertion that is
guaranteed to hold and that doesn't expose the internal granularity of
the duration.

Roman.