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Re: pthread question

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Geoff Clare wrote:
> 
> Alexander Terekhov wrote:
> 
> >
> > Geoff Clare wrote:
> > [...]
> >> 9. When a running thread issues the sched_yield() function, the
> >>    thread becomes the tail of the thread list for its priority.
> >
> > That makes sense for a uniprocessor.
> >
> > But nowadays even pocket gadgets are multiprocessors.
> >
> >> POSIX doesn't standardise internals, but it does standardise how
> >> threads with the above mentioned scheduling policies are scheduled.
> >
> > http://pubs.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_09.html
> >
> > "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."
> 
> Good point.  However, earlier in that section the standard says:
> 
> "It should be noted that the presence of multiple processors does not
> automatically indicate a scheduling allocation domain size greater
> than one. Conforming implementations on multi-processors may map all
> or any subset of the CPUs to one or multiple scheduling allocation
> domains"

That just says that the presence of multiple processors doesn't
guarantee parallel execution of threads. I'm talking about the case with
parallel execution of threads granted.

> 
> > 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.
Anyway since "implementation-defined" can change from version to version
by even the same vendor it does mean "no rules whatsoever" in disguise.

http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap01.html#tag_01_05_02

"implementation-defined

Describes a value or behavior that is not defined by POSIX.1-2008 but is
selected by an implementor. The value or behavior may vary among
implementations that conform to POSIX.1-2008. An application should not
rely on the existence of the value or behavior. An application that
relies on such a value or behavior cannot be assured to be portable
across conforming implementations."

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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