From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Fri, 05 Sep 2008 11:57:35 +0200
From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
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Subject: Re: [Xenomai-core] [PATCH 2/9] Switch to handle-based fast mutex
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To: Jan Kiszka <jan.kiszka@domain.hid>
Cc: xenomai-core <xenomai@xenomai.org>

Jan Kiszka wrote:
> Gilles Chanteperdrix wrote:
>> Jan Kiszka wrote:
>>> Gilles Chanteperdrix wrote:
>>>> Jan Kiszka wrote:
>>>>> @@ -230,18 +230,20 @@ static inline int mutex_save_count(xnthr
>>>>>  
>>>>>  	mutex = shadow->mutex;
>>>>>  
>>>>> -	if (clear_claimed(xnarch_atomic_intptr_get(mutex->owner)) != cur)
>>>>> +	if (clear_claimed(xnarch_atomic_get(mutex->owner)) !=
>>>>> +	    xnthread_handle(cur))
>>>>>  		return EPERM;
>>>>>  
>>>>>  	*count_ptr = shadow->lockcnt;
>>>>>  
>>>>> -	if (likely(xnarch_atomic_intptr_cmpxchg(mutex->owner, cur, NULL) == cur))
>>>>> +	if (likely(xnarch_atomic_cmpxchg(mutex->owner, cur, XN_NO_HANDLE) ==
>>>>> +		   xnthread_handle(cur)))
>>>>>  		return 0;
>>>>>  
>>>>>  	owner = xnsynch_wakeup_one_sleeper(&mutex->synchbase);
>>>>> -	xnarch_atomic_intptr_set
>>>>> -		(mutex->owner,
>>>>> -		 set_claimed(owner,xnsynch_nsleepers(&mutex->synchbase)));
>>>>> +	xnarch_atomic_set(mutex->owner,
>>>>> +			  set_claimed(xnthread_handle(owner),
>>>>> +				      xnsynch_nsleepers(&mutex->synchbase)));
>>>> Ok. Can we avoid xnthread_handle() everywhere by storing its result in a
>>>> local variable and reusing this local variable, here and in the other
>>>> functions where xnthread_handle is used multiple times ?
>>> True for 'cur' here (will fix), but the other case have already been
>>> optimized as far as possible (i.e. within the respective scope).
>> I have found several other spots where xnthread_handle is called
>> multiple times in the same function. mutex_unlock comes to my mind.
> 
> Please point me to the concrete spot. I went again through all
> xnthread_handle instances in this patch, checking that they aren't
> needed due to owner changes, but only found the one above. Specifically
> pthread_mutex_unlock, pse51_mutex_unlock_internal and
> __pthread_mutex_unlock have only a single reference or reference
> different threads.

Ok. I had grepped xnthread_handle and found that it was used twice in
mutex_unlock, but did not checked if it was used for the same thread.


-- 
                                                 Gilles.