Re: [Xenomai-core] [RFC][PATCH 2/3] Switch to handle-based fast mutex owners

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

Jan Kiszka wrote:
> Gilles Chanteperdrix wrote:
>> Jan Kiszka wrote:
>>> Gilles Chanteperdrix wrote:
>>>> Jan Kiszka wrote:
>>>>> +	xnarch_atomic_set(mutex->owner,
>>>>> +		 	  set_claimed(xnthread_handle(owner),
>>>>> +				      xnsynch_nsleepers(&mutex->synchbase)));
>>>> Ok. I think you have spotted a bug here. This should be mutex->sleepers
>>>> instead of xnsynch_nsleepers.
>>> BTW, why do you need to track sleepers separately in POSIX? Native
>>> doesn't do so, e.g.
>> Because of the "syscall-needed-when-unlocking-stolen-mutex" issue I
>> already explained (sleepers - xnsynch_nsleepers is precisely the count
>> of pending threads which have been awake then robbed the mutex).
> 
> Hmm, sounds like the new lock owner should better clear the 'claimed'
> bit then, not the old one on return from unlock. Or where is the
> pitfall? How does the futex algorithm handle this scenario?

Ok. Please read my explanation again, I have already explained this in
another mail.

-- 
                                                 Gilles.