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Re: Cygwin: Implement sched_[gs]etaffinity() commit breaks RTEMS port
On Fri, 2019-06-28 at 03:17 -0700, Mark Geisert wrote:
> On Fri, 28 Jun 2019, Sebastian Huber wrote:
> > On 28/06/2019 10:48, Mark Geisert wrote:
> >> On Thu, 27 Jun 2019, Corinna Vinschen wrote:
> >>> On Jun 27 08:28, Sebastian Huber wrote:
> >>>> On 26/06/2019 15:12, Corinna Vinschen wrote:
> >>>>> On Jun 26 13:05, Sebastian Huber wrote:
> >>>>>> On 26/06/2019 11:37, Corinna Vinschen wrote:
> >>>>>>> On Jun 26 10:24, Sebastian Huber wrote:
> >>>>>>>> Hello,
> >>>>>>>>
> >>>>>>>> the following commit:
> >>>>>>>>
> >>>>>>>> commit 641ecb07533e85211b6abce334c85967f3f90209
> >>>>>>>> Author: Mark Geisert<mark@maxrnd.com>
> >>>>>>>> Date: Sun Jun 23 14:51:06 2019 -0700
> >>>>>>>>
> >>>>>>>> Cygwin: Implement sched_[gs]etaffinity()
> >>>>>>>> [...]
> >>>>>>>> breaks the RTEMS port:
> >>>>>>>> [...]
> >>>>>>> Looks like Cygwin has to define its own sys/cpuset.h included via
> >>>>>>> sys/_pthreadtypes.h.
> >>>>>>
> >>>>>> Yes, something like this. The RTEMS <sys/cpuset.h> is based on the
> >>>>>> FreeBSD
> >>>>>> implementation and should be compatible to the Linux API. Maybe it can
> >>>>>> move
> >>>>>> out of the RTEMS area into the global Newlib area.
> >>>>>
> >>>>> I'm not so sure, given the different names of macros and types used
> >>>>> inside cpu_set_t. The new functions inside Cygwin rely on that.
> >>>>
> >>>> How do you implement this API in Cygwin:
> >>>>
> >>>> http://man7.org/linux/man-pages/man3/CPU_SET.3.html
> >>>>
> >>>> I think the RTEMS <sys/cpuset.h> implementation should cover it.
> >>>
> >>> AFAICS we don't.
> >>>
> >>> Mark, do you see much of a problem to rearrange your new
> >>> sched_[gs]etaffinity code to use the RTEMS sys/cpuset.h file?
> >>>
> >>> We can define our own sys/_cpuset.h, or use the RTEMS file as well.
> >>
> >> Hi folks,
> >> I was trying to minimize update scope while implementing the affinity calls
> >> from Linux for Cygwin. I noticed that taskset(1), from the util-linux
> >> package, supplies its own CPU_SET implementation (copied from glibc) so I
> >> decided to not supply one for Cygwin but let taskset use its own. I felt
> >> we could add CPU_SET to Cygwin when necessary, later.
> >>
> >> The macro #defines I added to sched.h are those needed by Linux CPU_SET
> >> regardless of how it gets defined. I worry about trying to use a FreeBSD
> >> based CPU_SET -- just from unfamiliarity.
> >
> > The RTEMS <sys/cpuset.h> implements the Linux and FreeBSD APIs. In case of
> > conflict (and there are conflicts, the libc developers should talk more with
> > each other) we choose the Linux variant.
>
> O.K. Thank you for the background.
>
> >>
> >> Corinna, I see how your workaround patch moves my macros to Cygwin's
> >> sys/cpuset.h. That seems fine to me.
> >>
> >> I don't see how the include linkage through _pthreadtypes.h works though.
> >> How does a user app including <sched.h> get <sys/cpuset.h> pulled in?
> >
> > It is included via <sys/types.h> -> <sys/_pthreadtypes.h> -> <sys/cpuset.h>.
>
> Great! Thank you Sebastian.
>
> Corinna, I'm able to build Cygwin 64- and 32-bit with your updates, and to
> build util-linux as well. I have a resulting working taskset executable.
>
> It was not necessary to implement the CPU_SET functionality via any of the
> possible ways because taskset supplies its own if it can't find one.
>
> We can call it a day, with review and release of the current patch state.
> If you think it's worthwhile to implement CPU_SET on Cygwin now, rather
> than later, I can look into it but it's not strictly necessary at this
> time.
We shouldn't be do things half-way. taskset may not require it, but
any use of CPU sets could very well expect this to be present:
http://man7.org/linux/man-pages/man3/CPU_SET.3.html
--
Yaakov Selkowitz
Senior Software Engineer - Platform Enablement
Red Hat, Inc.