Gilles Chanteperdrix wrote:
> Jan Kiszka wrote:
>> Gilles Chanteperdrix wrote:
>>> Jan Kiszka wrote:
>>>> To improve robustness of the fast mutex implementation in POSIX (and
>>>> later on in native), it is better to track the mutex owner by handle
>>>> instead of kernel object pointer. Therefore, this patch changes
>>>> __xn_sys_current (xeno_set_current) so that it returns
>>>> xnthread_handle(current_thread). It furthermore converts the POSIX mutex
>>>> implementation to pick up and store the lock owner as handle in the
>>>> kernel/user-shared mutex. Finally it ensures that all skins (except for
>>>> RTDM which must not mess around with foreign skins anyway) add their
>>>> threads to the registry so that at least anonymous handles are
>>>> available.
>>>>
>>>> As the value stored in the mutex variable is now an integer, we can
>>>> switch over to xnarch_atomic_t, removing all atomic_intptr users.
>>> The current implementation allows RTDM threads to use POSIX skin
>>> mutexes. I do not see why this should change.
>> Such mixup might technically be possible now. But there is neither a
>> need nor does it make the resulting driver more portable. I don't want
>> to introduce needless thread registration to RTDM just to cover
>> theoretical use cases that should not exist in the first place.
>>
>> Nevertheless, some sanity check will have to be added to the
>> to-be-written generic xnsynch support to catch missing thread handles.
>> That make sense for checking future skin implementation as well.
> 
> That is overhead in the hot path, whereas adding the thread registration
> takes place in a non hot path.

It will be a debug check.

Jan

-- 
Siemens AG, Corporate Technology, CT SE 2
Corporate Competence Center Embedded Linux

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