Jan Kiszka wrote:
> 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.
Ok. But the other points remain.
--
Gilles.
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