Proper algorithm for return values from sleep

John Baldwin jhb at FreeBSD.org
Mon Mar 1 12:57:54 PST 2004


On Friday 27 February 2004 08:25 pm, David Xu wrote:
> John Baldwin wrote:
> > As part of my sleep queue work, I found that msleep() and the cv_wait()
> > functions have differing semantics for return vales.  It appears that at
> > least some of the early changes KSE made to msleep() were ported to cv's
> > but not later cleanups.  Specifically, in msleep(), if we are awakened
> > while checking for signals but we didn't find a signal, we prefer a
> > timeout-related return value over a signal-related value.
>
> Yes, I think cv and msleep code should be synchronized.
>
> > Secondly, cv's don't really handle
> > td_intrval very well at all.
>
> It is a bug. :-(
>
> > It has one hard-coded override for the P_EXIT
> > case but that's it.
>
> I think it should includes P_SINGLE_EXIT, P_WEXIT is set when there is
> only one thread in process (see exit1() ). both msleep and cv are
> incorrect in the case.
>
> Are you fixing these bugs ?

Well, I'll fix them if I can figure out what the correct algorithm should 
be. :)  Do you think you could sketch it out in psuedo-code?

-- 
John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org


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