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Document the implications of the callout_stop() returning 0 if the

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callout has finished or is in progress.  Also document that the
locking of the callout code for FreeBSD 5 has eliminated the 'or is in
progress' clause as a possibility and that such elimination is an
accident of the implementation and shouldn't be relied upon.
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imp 2003-10-01 05:48:48 +00:00
parent 8155be3845
commit 002709d385
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14
share/man/man9/timeout.9
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@ -204,6 +204,20 @@ that can be passed to
The
.Fn callout_stop
function returns non-zero if the callout is still pending or zero otherwise.
.Sh BUGS
This API has no way to cancel a callback and ensure that if it was
cancelled too late that the callback has actually finished.
.Fn callout_stop
only guarantees that the callback has started when it returns 0.
It does not guarnatee that the callback has finished.
This can create a race when one wishes to ensure that no threads are
executing before returning from a driver detach routine.
The locking scheme currently used ensures that a
.Fn callout_stop
will not return until after the callout has been dequeued or has
finished running.
This locking is an accident of the implementation and is not
guarnateed by the interface.
.Sh HISTORY
The current timeout and untimeout routines are based on the work of
.An Adam M. Costello