Condition Variables for RTEMS

zhang json json.a.zhang at
Fri Feb 28 00:12:50 UTC 2014

Hi Gedare,

2014-02-26 1:07 GMT+08:00 Gedare Bloom <gedare at>:

> You may like to read
> in addition to the Condition Variables project page. You can search
> for "condition variable" in a search engine to get some useful
> background material. More below.
> Thank you for your reply. I will search and prepare this project and a
draft will be post ASAP.

> On Tue, Feb 25, 2014 at 9:45 AM, zhang json <json.a.zhang at>
> wrote:
> > Hi all,
> >
> > I am a student who is preparing for participating  the GSOC2014, and from
> > 'Open Project' i found a interesting project 'Condition Variables'. So i
> > want to know the basic information about the status of this project.
> >
> > There is a bug [1] which is maybe related to it but it seems that
> > 'Condition Variables' is not the main problem of this bug. So my
> confusion
> > is blow:
> >
> > 1. As one of the classic operating system synchronization primitives
> whether
> > RTEMS has a basic 'Condition Variables' support?
> RTEMS lacks a condition variable (monitor) implementation within the
> classic API located in cpukit/rtems/*, and also within the supercore
> "kernel" interface located in cpukit/score/*. There is condition
> variables support in posix, as the
> cpukit/posix/include/rtems/posix/condimpl.h.
> OK, i have some rtems experience so i will first design the CV and
implement it in score component, then warp it into classic api.

> > 2. If answer not from 1, what is the requirement of the implementation?
> It should implement a classic API condition variable that can be
> similar to the classic API implementation of semaphore
> (cpukit/rtems/include/rtems/rtems/sem.h and semimpl.h). The condition
> variable should be implemented in the supercore (cpukit/score) and
> that implementation should be shared by the posix condvar and the
> classic API condition variables.
> Yeah, i will refer to implementation of semaphore and mutex. And there are
lots of open source CV implementation for many os, such freebsd, netbsd,
linux, eCos. About linux its license may be is not compatible with RTEMS,
so i just learn its idea instead of code.

> > 3. Whether its implementation should support SMP?
> >
> The implementation must support SMP.
Yeah, it will be a challenge. But as i know the SMP support of RTEMS is
becoming better, some SMP synchronization primitives have been support,
like atomic. I am wondering whether semaphore and mutex is supported SMP?

> Gedare
> >
> >
> > 1.
> >
> > _______________________________________________
> > rtems-devel mailing list
> > rtems-devel at
> >
> >

Json Zhang
Best Regards
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