[PATCH rtems 1/2] Add support for CONFIGURE_POSIX_TIMERS_FACE_BEHAVIOR

Sebastian Huber sebastian.huber at embedded-brains.de
Fri Aug 5 14:25:49 UTC 2022


On 05/08/2022 16:14, Joel Sherrill wrote:
> 
> 
> On Fri, Aug 5, 2022 at 5:45 AM Sebastian Huber 
> <sebastian.huber at embedded-brains.de 
> <mailto:sebastian.huber at embedded-brains.de>> wrote:
> 
>     On 05/08/2022 00:08, Joel Sherrill wrote:
>      > This adds the configure option CONFIGURE_POSIX_TIMERS_FACE_BEHAVIOR
>      > which allows the application to choose whether to have the POSIX
>      > timer_create() function follow the behavior defined by POSIX or
>      > the FACE Technical Standard.
>      >
>      > Updates #4691.
> 
>     It would be nice if you could add items for the new option to
>     rtems-central so that we can use it for the Doxygen documentation and
>     the manual.
> 
> 
> I'll give it a try. Is there a readme or really good example?

There is this:

https://docs.rtems.org/branches/master/eng/req/howto.html#

> 
> 
>      > ---
>      >   cpukit/include/rtems/confdefs.h                    |  1 +
>      >   cpukit/include/rtems/confdefs/face.h               | 71
>     +++++++++++++++++
>      >   cpukit/include/rtems/posix/timerimpl.h             | 11 +++
>      >   cpukit/posix/src/psxtimercreate.c                  | 19 ++++-
>      >   spec/build/testsuites/psxtests/grp.yml             |  2 +
>      >   spec/build/testsuites/psxtests/psxtimer_face01.yml | 20 +++++
>      >   testsuites/psxtests/psxtimer_face01/psxtimer.c     | 89
>     ++++++++++++++++++++++
>      >   .../psxtests/psxtimer_face01/psxtimer_face01.doc   | 39 ++++++++++
>      >   .../psxtests/psxtimer_face01/psxtimer_face01.scn   |  4 +
>      >   9 files changed, 255 insertions(+), 1 deletion(-)
>      >   create mode 100644 cpukit/include/rtems/confdefs/face.h
>      >   create mode 100644
>     spec/build/testsuites/psxtests/psxtimer_face01.yml
>      >   create mode 100644 testsuites/psxtests/psxtimer_face01/psxtimer.c
>      >   create mode 100644
>     testsuites/psxtests/psxtimer_face01/psxtimer_face01.doc
>      >   create mode 100644
>     testsuites/psxtests/psxtimer_face01/psxtimer_face01.scn
>      >
>      > diff --git a/cpukit/include/rtems/confdefs.h
>     b/cpukit/include/rtems/confdefs.h
>      > index e6dd3d7..3927d26 100644
>      > --- a/cpukit/include/rtems/confdefs.h
>      > +++ b/cpukit/include/rtems/confdefs.h
>      > @@ -64,6 +64,7 @@
>      >   #include <rtems/confdefs/clock.h>
>      >   #include <rtems/confdefs/console.h>
>      >   #include <rtems/confdefs/extensions.h>
>      > +#include <rtems/confdefs/face.h>
>      >   #include <rtems/confdefs/inittask.h>
>      >   #include <rtems/confdefs/initthread.h>
>      >   #include <rtems/confdefs/iodrivers.h>
>      > diff --git a/cpukit/include/rtems/confdefs/face.h
>     b/cpukit/include/rtems/confdefs/face.h
>      > new file mode 100644
>      > index 0000000..07ab62e
>      > --- /dev/null
>      > +++ b/cpukit/include/rtems/confdefs/face.h
>      > @@ -0,0 +1,71 @@
>      > +/* SPDX-License-Identifier: BSD-2-Clause */
>      > +
>      > +/**
>      > + * @file
>      > + *
>      > + * @ingroup RTEMSImplApplConfig
>      > + *
>      > + * @brief This header file evaluates configuration options
>     related to
>      > + *   the FACE Technical Standard.
>      > + *
>      > + * The FACE Technical Standard (https://opengroup.org/face
>     <https://opengroup.org/face>) is an
>      > + * open standard designed for safety critical embedded systems. It
>      > + * includes POSIX profiles and requirements that promote safety
>      > + * and portability. As a general rules, the profiles place a minimum
>      > + * on the services which an operating system must provide. Those
>      > + * same profile definitions represent the maximum services which
>      > + * an application may use.
>      > + */
>      > +
>      > +/*
>      > + * Copyright (C) 2022 On-Line Applications Research Corporation
>     (OAR)
>      > + *
>      > + * Redistribution and use in source and binary forms, with or
>     without
>      > + * modification, are permitted provided that the following
>     conditions
>      > + * are met:
>      > + * 1. Redistributions of source code must retain the above copyright
>      > + *    notice, this list of conditions and the following disclaimer.
>      > + * 2. Redistributions in binary form must reproduce the above
>     copyright
>      > + *    notice, this list of conditions and the following
>     disclaimer in the
>      > + *    documentation and/or other materials provided with the
>     distribution.
>      > + *
>      > + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
>     CONTRIBUTORS "AS IS"
>      > + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
>     LIMITED TO, THE
>      > + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
>     PARTICULAR PURPOSE
>      > + * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
>     CONTRIBUTORS BE
>      > + * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
>     EXEMPLARY, OR
>      > + * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
>     PROCUREMENT OF
>      > + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
>     OR BUSINESS
>      > + * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
>     WHETHER IN
>      > + * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
>     OTHERWISE)
>      > + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
>     ADVISED OF THE
>      > + * POSSIBILITY OF SUCH DAMAGE.
>      > + */
>      > +
>      > +#ifndef _RTEMS_CONFDEFS_FACE_H
>      > +#define _RTEMS_CONFDEFS_FACE_H
>      > +
>      > +#ifndef __CONFIGURATION_TEMPLATE_h
>      > +#error "Do not include this file directly, use
>     <rtems/confdefs.h> instead"
>      > +#endif
>      > +
>      > +#ifdef CONFIGURE_INIT
>      > +
>      > +#include <rtems/posix/timerimpl.h>
>      > +
>      > +#ifndef CONFIGURE_POSIX_TIMERS_FACE_BEHAVIOR
>      > +  bool _POSIX_Timer_Is_allowed_on_CLOCK_REALTIME( void )
>      > +  {
>      > +    /*
>      > +     * Per the FACE Technical Standard, POSIX timers should not be
>      > +     * allowed on CLOCK_REALTIME for safety reasons. If the
>     application
>      > +     * wants the FACE behavior, then this method is instantiated.
>      > +     */
>      > +    return false;
>      > +  }
> 
>     I would change this to:
> 
>     int _POSIX_Timer_Is_clock_valid( clockid_t clock_id )
> 
>     It returns an error number or zero.
> 
> 
> Perhaps OK on errno or zero but that name isn't right. CLOCK_REALTIME
> is still a valid POSIX clock. There are just strict requirements around its
> use for the FACE profiles. That name implies a general validity. The 
> requirement
> is specifically around creating a timer that uses CLOCK_REALTIME.

Maybe name it _POSIX_Timer_Is_clock_allowed(). The benefit of using an 
error number return is that this avoids dead code for the default case.

> 
> Previous work has addressed the other restrictions. The TOD Hook
> additions do allow a BSP to sync an RTC but the FACE purpose was
> to check if the application (e.g. partition/virtual space) has permission
> to set the clock.
> 
> 
>      > +
>      > +#endif /* CONFIGURE_POSIX_TIMERS_FACE_BEHAVIOR */
>      > +
>      > +#endif /* CONFIGURE_INIT */
>      > +
>      > +#endif /* _RTEMS_CONFDEFS_FACE_H */
>      > diff --git a/cpukit/include/rtems/posix/timerimpl.h
>     b/cpukit/include/rtems/posix/timerimpl.h
>      > index 8f92186..c6e3b64 100644
>      > --- a/cpukit/include/rtems/posix/timerimpl.h
>      > +++ b/cpukit/include/rtems/posix/timerimpl.h
>      > @@ -139,6 +139,17 @@ RTEMS_INLINE_ROUTINE void _POSIX_Timer_Release(
>      >     _ISR_lock_ISR_enable( lock_context );
>      >   }
>      >
>      > +/**
>      > + * @brief Follow POSIX or FACE Technical Standard on timer_create
>      > + *
>      > + * POSIX allows for the creation of timers based on CLOCK_REALTIME.
>      > + * This is viewed as a safety issue by the FACE Technical Standard
>      > + * and required to return an error. These are conflicting behaviors.
>      > + * This method is instanced by configuration when FACE conformant
>      > + * behavior is desired by the application.
>      > + */
>      > +RTEMS_WEAK bool _POSIX_Timer_Is_allowed_on_CLOCK_REALTIME( void );
> 
>     No RTEMS_WEAK in the header file.
> 
> 
> OK. Need another include file clearly.

It should move to <rtems/posix/timer.h> which is included by confdefs.h.

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