[rtems commit] Using the generic atomic ops to implement UP mode atomic for all architectures . SMP atomic port will be later.

[wei.a.yang]

在 2013-5-1，23:19，Ralf Corsepius <ralf.corsepius at rtems.org> 写道：

> On 05/01/2013 05:00 PM, Joel Sherrill wrote:
>> On 5/1/2013 9:44 AM, Ralf Corsepius wrote:
>>> On 05/01/2013 04:23 PM, Gedare Bloom wrote:
>>>> Module:    rtems
>>>> Branch:    master
>>>> Commit:    9b605b28b497f398682a8ffd673f6860340957f8
>>>> Changeset: http://git.rtems.org/rtems/commit/?id=9b605b28b497f398682a8ffd673f6860340957f8
>>>> 
>>>> Author:    WeiY <wei.a.yang at gmail.com>
>>>> Date:      Wed Apr 24 00:34:16 2013 +0800
>>>> 
>>>> Using the generic atomic ops to implement UP mode atomic for all architectures. SMP atomic port will be later.
>>>> +++ b/cpukit/score/cpu/arm/rtems/score/cpuatomic.h
>>>> @@ -0,0 +1,40 @@
>>>> +/**
>>>> + * @file  rtems/score/cpuatomic.h
>>>> + *
>>>> + * This include file implements the atomic operations for arm and defines
>>>> + * atomic data types which are used by the atomic operations API file. This
>>>> + * file should use fixed name cpuatomic.h and should be included in atomic
>>>> + * operations API file atomic.h. If the architecture works at the UP mode it
>>>> + * will use a generic atomic ops using disable/enable-IRQ simulated. If the
>>>> + * the architecture works at SMP mode, most of the parts of implementations
>>>> + * are imported from FreeBSD kernel.
>>>> + */
>>>> +
>>>> +#ifndef _RTEMS_SCORE_ATOMIC_CPU_H
>>>> +#define _RTEMS_SCORE_ATOMIC_CPU_H
>>>> +
>>>> +#include <rtems/score/genericcpuatomic.h>
>>>> +
>>>> +#ifdef __cplusplus
>>>> +extern "C" {
>>>> +#endif
>>>> +
>>>> +/**
>>>> + * @defgroup RTEMS atomic implementation
>>>> + *
>>>> + */
>>>> +
>>>> +/**@{*/
>>>> +
>>>> +#if !defined(RTEMS_SMP)
>>>> +#include <rtems/score/genericatomicops.h>
>>>> +#else
>>>> +#endif
>>>> +
>>>> +#ifdef __cplusplus
>>>> +}
>>>> +#endif
>>>> +
>>>> +/**@}*/
>>>> +#endif
>>>> +/*  end of include file */
>>> Would somebody please explain the code above?
>>> 
>>> The #ifdef __cplusplus as well as the #if !defined(RTEMS_SMP)
>>> should be completely superflous. If not, they'd indicate bugs elsewhere.
>> AFAIK The !defined(RTEMS_SMP) just says use the generic uniprocessor
>> implementation when not SMP. What's the specific issue?
> The code includes
> <rtems/score/genericatomicops.h>
> twice. Once unconditionally and once conditionally.
> This is redundant.
> 
No, the first time it includes genericcpuatomic.h instead of genericatomicops.h. So it is not redundant.
> 
>> 
>> And I also don't see what the issue is with the C++ check.
> The c++ guard is entirely superfluous in this case, because the file does not define any symbol.
> 
> 
>> A quick
>> grep of score shows 122 files or 333 .h files have the C++ guard.
>> Do you have a rationale for when one should be present or not?
> The guards are required when files defines/declares C symbols. Files which don't, don't have to.
> 
> Finally, files should set c++ guards in ways they are self-contained. The construct above guards an included file, which means this guard is either redundant (in case the other file is self-guarded) or the included file isn't self-guarded (which would mean the include file is poorly implemented == broken).
> 
> Ralf
> 
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