OK, thanks. I have filed a bug in the bugzilla:
https://bugs.open64.net/show_bug.cgi?id=660
On Tue, Sep 21, 2010 at 3:15 PM, Tianwei <tianwei.sh...@gmail.com> wrote:
> Forget to mention, your fix is good, you can check in that and record that
> in the bug database.
>
> Tianwei
>
> On Tue, Sep 21, 2010 at 2:56 PM, Tianwei <tianwei.sh...@gmail.com> wrote:
>
>> I think it is a real data races bugs, or an order violation(the order of
>> two write operations), look at the following the scenario, (we just treat
>> *lock) as a normal global shared struct variable X and it has two
>> membersas:
>> struct X ｛
>> BOOL initialized_flags
>> int data
>> }
>>
>> struct X x;
>> thread1:
>>
>> if( x.data == NULL) {
>> lock
>> x.initialized_flags =
>> x.data = initialized_variables
>> unlock
>> }
>> = x.data ( it's first use)
>>
>> we must enforce that x.data is used after its initialization. I think
>> your fix is a very good fix. Please file a bug in the bugzillar.
>>
>> Thanks for your great finding.
>>
>> Tianwei
>>
>> On Tue, Sep 21, 2010 at 1:21 PM, Jiangzhou HE <hejiangz...@gmail.com>wrote:
>>
>>> Hi, all,
>>>
>>> I found a bug in osprey/libopenmp/omp_lock.c. See the following function:
>>>
>>> inline void
>>> __ompc_critical(int gtid, volatile ompc_lock_t **lck)
>>> {
>>> if (**lck == NULL*) { *//(1)*
>>> __ompc_lock_spinlock(&_ompc_thread_lock);
>>> if ((ompc_lock_t*)*lck == NULL){
>>> // put the shared data aligned with cache line
>>> * *lck = aligned_malloc(sizeof(ompc_lock_t), CACHE_LINE_SIZE);
>>> //(2)
>>> * Is_True(*lck!=NULL,
>>> ("Cannot allocate lock memory for critical"));
>>> * __ompc_init_lock (*lck); //(3)*
>>> }
>>> __ompc_unlock_spinlock(&_ompc_thread_lock);
>>> }
>>> *__ompc_lock((volatile ompc_lock_t *)*lck);* *//(4)*
>>> }
>>>
>>> Bug happens in the following execution sequence:
>>>
>>> thread1 thread2
>>> (1)
>>> (2)
>>> (1)
>>> (4) *// Error! Trying to lock a uninitialized lock.*
>>> (3)
>>>
>>> This is my patch of this bug:
>>>
>>> diff --git a/osprey/libopenmp/omp_lock.c b/osprey/libopenmp/omp_lock.c
>>> index 0781647..718117c 100644
>>> --- a/osprey/libopenmp/omp_lock.c
>>> +++ b/osprey/libopenmp/omp_lock.c
>>> @@ -197,10 +197,11 @@ __ompc_critical(int gtid, volatile ompc_lock_t
>>> **lck)
>>> __ompc_lock_spinlock(&_ompc_thread_lock);
>>> if ((ompc_lock_t*)*lck == NULL){
>>> // put the shared data aligned with cache line
>>> - *lck = aligned_malloc(sizeof(ompc_lock_t), CACHE_LINE_SIZE);
>>> - Is_True(*lck!=NULL,
>>> + volatile ompc_lock_t* new_lock =
>>> aligned_malloc(sizeof(ompc_lock_t), CACHE_LINE_SIZE);
>>> + Is_True(new_lock!=NULL,
>>> ("Cannot allocate lock memory for critical"));
>>> - __ompc_init_lock (*lck);
>>> + __ompc_init_lock (new_lock);
>>> + *lck = new_lock;
>>> }
>>> __ompc_unlock_spinlock(&_ompc_thread_lock);
>>> }
>>>
>>> Could the gatekeeper help to review this patch?
>>>
>>> Thanks!
>>>
>>> Jiangzhou
>>>
>>> --
>>> Jiangzhou HE (何江舟)
>>>
>>> Institute of High-Performance Computing
>>> Department of Computer Science and Technology
>>> Tsinghua University, Beijing, China
>>>
>>>
>>>
>>> ------------------------------------------------------------------------------
>>> Start uncovering the many advantages of virtual appliances
>>> and start using them to simplify application deployment and
>>> accelerate your shift to cloud computing.
>>> http://p.sf.net/sfu/novell-sfdev2dev
>>> _______________________________________________
>>> Open64-devel mailing list
>>> Open64-devel@lists.sourceforge.net
>>> https://lists.sourceforge.net/lists/listinfo/open64-devel
>>>
>>>
>>
>>
>> --
>> Sheng, Tianwei
>> Inst. of High Performance Computing
>> Dept. of Computer Sci. & Tech.
>> Tsinghua Univ.
>>
>
>
>
> --
> Sheng, Tianwei
> Inst. of High Performance Computing
> Dept. of Computer Sci. & Tech.
> Tsinghua Univ.
>
--
Jiangzhou HE (何江舟)
Institute of High-Performance Computing
Department of Computer Science and Technology
Tsinghua University, Beijing, China
------------------------------------------------------------------------------
Start uncovering the many advantages of virtual appliances
and start using them to simplify application deployment and
accelerate your shift to cloud computing.
http://p.sf.net/sfu/novell-sfdev2dev
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