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Date: Wed, 07 Apr 2004 02:19:13 +0100
To: Nate Lawson <nate@root.org>
From: Colin Percival <colin.percival@wadham.ox.ac.uk>
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cc: Colin Percival <colin.percival@wadham.ox.ac.uk>
Subject: Re: cvs commit: src/sys/kern kern_timeout.c src/sys/sys 
 callout.h src/share/man/man9 timeout.9
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At 01:54 07/04/2004, Nate Lawson wrote:
>Nope, you've already included the check in your text so it can move as-is.
>Consider this example:
>
>+                       if (wakeup_needed) {
>+                               /*
>+                               * There might be someone waiting
>+                               * for the callout to complete.
>+                               */
>
>wakeup_needed being non-zero means there is someone waiting for the
>callout to complete.

  No.  I wrote that comment very carefully; wakeup_needed being nonzero
means that there *might* be someone waiting for the callout to complete.
It's possible that the thread which wants to wait hasn't actually reached
cv_wait() yet -- thus the games with wakeup_ctr, wakeup_done_ctr, and
wakeup_cookie.

Colin Percival