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About CCriticalSection

Posted on 1998-11-18
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Last Modified: 2013-11-20
Hi!
I have some threads, which can call a function from a single
object, let's say CBoss.
 When I declare a CCriticalSection class in the header of
CBoos (       CCriticalSection m_readSection;)
and I try to access the function of this class from a thread-class in the next way:

CSingleLock m_readSection(&m_pDoc->m_readSection, FALSE);
m_readSection.Lock(INFINITE);
m_pDoc->ReadMsg(pMsg, this);
m_readSection.Unlock();

the thread stops on the second Lock (i.e. when I try to lock the second time the CriticalSection, the thread begin to wait, even if the CSingleLock object - m_readSection is
not locked- I have checked this). There is only one thread,
so doesn't exist another thread to lock this critical section.

When I use in the CBoss header       

static CRITICAL_SECTION m_readSect;
and I try to access the function of this class from a thread class in the next way:
EnterCriticalSection(&m_pDoc->m_readSect);
{
      m_pDoc->ReadMsg(pMsg, this);
}
LeaveCriticalSection(&m_pDoc->m_readSect);

it's OK.

What's wrong with the use of MFC classes?





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Question by:visualc
2 Comments
 
LVL 15

Accepted Solution

by:
Tommy Hui earned 100 total points
ID: 1324929
The problem is you are passing the critical section by value. Generally this makes a copy and most MFC classes do not have copy semantics. You should pass the critical section by reference (CCriticalSection&) or by pointer (CCriticalSection*).
0
 

Author Comment

by:visualc
ID: 1324930
Hi,
I think that is another problem, because if I modify the declaration of m_readSection to
CCriticalSection* m_readSection;
and I use in this way -->
CSingleLock m_readSection(m_pDoc->m_readSection, FALSE);
if (m_readSection.IsLocked())
    MessageBeeP(1000);
m_readSection.Lock(INFINITE);
m_pDoc->ReadMsg(pMsg, this);
m_readSection.Unlock();

the problem is the same. When I try the second time, the code doesn't reach the MessageBeep command, so the CriticalSection is unlocked, but when I try to lock, the thread stops.
I don't have any idea, why.
0

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