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Re: pthread question

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Geoff Clare wrote:
> 
> Alexander Terekhov wrote:
> 
> >
> > Geoff Clare wrote:
> > [...]
> >> >> > "For application threads with scheduling allocation domains of size
> >> >> > greater than one, the rules defined for SCHED_FIFO, SCHED_RR, [TSP] and
> >> >> > SCHED_SPORADIC shall be used in an implementation-defined manner."
> >> >> >
> >> >> > Translation: no rules whatsoever.
> >> >>
> >> >> The way the domain-size-one rules are applied to larger domains is
> >> >> "implementation-defined", which means implementations are required
> >> >> to document how they are applied.  Not quite the same as "no rules
> >> >> whatsoever".
> >> >
> >> > In praxis "implementation-defined" means undocumented to begin with.
> >>
> >> Huh?  XBD7 section 2.1.2:
> >>
> >>     A conformance document with the following information shall be
> >>     available for an implementation claiming conformance to POSIX.1-2008.
> >>     [...]
> >>     The conformance document shall describe the behavior of the
> >>     implementation for all implementation-defined features defined in
> >>     POSIX.1-2008. This requirement shall be met by listing these
> >>     features and providing either a specific reference to the system
> >>     documentation or providing full syntax and semantics of these
> >>     features.
> >>
> >> > Anyway since "implementation-defined" can change from version to version
> >> > by even the same vendor it does mean "no rules whatsoever" in disguise.
> >>
> >> No, it means each implementor chooses their own rules, but they must
> >> tell you what those rules are.  . . .
> >
> > Well, at
> >
> > http://www.opengroup.org/csq/public/search.mhtml?t=XY1&sort=bycomponent
> >
> > I can't find anything regarding rules for scheduling allocation domains
> > of size greater than one. Do you have a link?
> 
> The Open Group's CSQs don't cover everything the POSIX Conformance
> Document (PCD) has to cover.
> 
> Originally I think the idea was that the PCD would be supplied with
> the system's developer documentation.  Of course, these days it
> would make sense for them to be provided online, but it's up to
> each implementor how they want to provide it.  It does seem that
> they are not easy to find online.  I was able to find one for
> HP-UX, but it was an old one from before pthreads were added to the
> standard. One that I did find with the relevant information is for
> QNX:
> 
> www.qnx.com/developers/docs/6.5.0/topic/com.qnx.doc.neutrino_prog/posix_conformance.html
> 
> According to that document, this is what QNX does:
> 
>     For threads with scheduling allocation domains of size greater
>     than one, the rules defined for SCHED_FIFO, SCHED_RR, and
>     SCHED_SPORADIC are followed such that if the thread becomes the
>     head of its thread list, the thread may become the runnable thread
>     on any processor in its scheduling allocation domain if it has a
>     higher priority than the running thread on one of those processors.
> 
>     This may in turn result in the preempted thread's becoming the
>     running thread on a different processor if that thread also has a
>     scheduling allocation domain of size greater than one and its
>     priority is higher than the running thread on one of the other
>     processors in its scheduling allocation domain.
> 
>     If a thread's scheduling allocation domain has a size greater than
>     one, a runnable thread selects the processor on which it becomes
>     the runnable thread as follows:
> 
>       1. For each processor in the thread's scheduling allocation domain,
>       find the processor whose running thread has the lowest priority
>       that is less than this thread.
> 
>       2. If the search identifies only one processor, select that
>       processor and make the thread the running thread on that processor.
> 
>       3. If the search identifies more than one processor, select the
>       processor on which the thread previously ran before becoming a
>       blocked thread.
> 
>       4. If the thread hadn't run on any of the selected processors
>       before becoming a blocked thread, select the first processor
>       that was found in the search.

Thanks.

The thing is that (priorities aside) in the case of T threads running on
P processors with P = T (all threads can run in parallel, priorities are
irrelevant), sched_yield() is supposed to be a no-op, do you agree?

regards,
alexander.

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pthread question p6 c6d6 <p6c6d6@gmail.com> - 2011-05-08 21:28 -0700
  Re: pthread question Vaclav Haisman <v.haisman@sh.cvut.cz> - 2011-05-09 07:11 +0200
  Re: pthread question Joshua Maurice <joshuamaurice@gmail.com> - 2011-05-09 11:49 -0700
    Re: pthread question David Schwartz <davids@webmaster.com> - 2011-05-09 12:24 -0700
      Re: pthread question Joshua Maurice <joshuamaurice@gmail.com> - 2011-05-09 14:22 -0700
        Re: pthread question "Chris M. Thomasson" <cristom@charter.net> - 2011-05-09 15:33 -0700
        Re: pthread question David Schwartz <davids@webmaster.com> - 2011-05-10 01:22 -0700
    Re: pthread question Geoff Clare <geoff@clare.See-My-Signature.invalid> - 2011-05-10 13:47 +0100
      Re: pthread question Alexander Terekhov <terekhov@web.de> - 2011-05-10 17:53 +0200
        Re: pthread question Geoff Clare <geoff@clare.See-My-Signature.invalid> - 2011-05-11 13:46 +0100
          Re: pthread question Alexander Terekhov <terekhov@web.de> - 2011-05-11 16:19 +0200
            Re: pthread question Geoff Clare <geoff@clare.See-My-Signature.invalid> - 2011-05-12 13:26 +0100
              Re: pthread question Alexander Terekhov <terekhov@web.de> - 2011-05-12 15:28 +0200
                Re: pthread question Geoff Clare <geoff@clare.See-My-Signature.invalid> - 2011-05-13 14:00 +0100
                Re: pthread question Alexander Terekhov <terekhov@web.de> - 2011-05-13 22:59 +0200
                Re: pthread question Geoff Clare <geoff@clare.See-My-Signature.invalid> - 2011-05-16 13:28 +0100

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