cvs commit: src/share/man/man9 sleep.9

Robert Watson rwatson at
Mon Mar 5 09:36:22 UTC 2007

On Sun, 4 Mar 2007, Greg Lehey wrote:

> grog        2007-03-04 23:42:58 UTC
>  FreeBSD src repository
>  Modified files:
>    share/man/man9       sleep.9
>  Log:
>  Rearrange function descriptions in more logical order.
>  Be less alarmist about the dangers of abusing wakeup_one().

How would you feel about language along the lines of:

   Prior to the introduction of wakeup_one(), using a single wait channel
   address was possible as long as all sleepers looped around the sleep call
   re-checking the condition after each wakeup.  However, with the addition of
   wakeup_one(), combining wait channels for multiple purposes may lead easily
   to bugs involving lost wakeups, and is strongly discouraged.  It is
   recommended that consumers of the sleep(9) programming interface carefully
   follow the convention of using only wait channels associated with memory
   addresses explicitly allocated for this purpose, and not overload or extend
   the semantics of existing wait channels without careful analysis in order to
   avoid potential channel collisions.  Programmers may find the cv(9)
   interface easier to use correctly, as it has explicit condition variable
   data structures.

That way we combine warnings about potential misuse with a recommendation for 
the cv(9) API.

Robert N M Watson
Computer Laboratory
University of Cambridge

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