关于多线程里内存分配的问题，望高手解答 - developer discussion boards.mht

symbian的学习笔记

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      <DIV class=3Dsmallfont style=3D"MARGIN-BOTTOM: 2px">Quote:</DIV>
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          <TD class=3Dalt2=20
          style=3D"BORDER-RIGHT: 1px inset; BORDER-TOP: 1px inset; =
BORDER-LEFT: 1px inset; BORDER-BOTTOM: 1px inset">Overview:<BR>Calls=20
            like User::Alloc() and User::Available() are not thread safe =
if used=20
            in multiple threads with a shared heap.<BR>Detailed=20
            description:<BR>User::Alloc() and User::Available() calls =
are not=20
            thread safe by themselves. In a multithreaded application it =
is=20
            possible for the parent thread to specify the heap used by a =
child=20
            thread. There are two options: dedicated heap and shared =
heap. If=20
            two or more threads operate on a shared heap, then =
synchronization=20
            (e.g. with mutexes) is required.<BR>Solution:<BR>1) Shared=20
            heap:<BR>IMPORT_C TInt Create( const TDesC=20
            &amp;aName,<BR>TThreadFunction aFunction,<BR>TInt=20
            aStackSize,<BR>RAllocator *aHeap,<BR>TAny =
*aPtr,<BR>TOwnerType aType=20
            =3D EOwnerProcess ); <BR>If the aHeap parameter is set as =
NULL in the=20
            above call, then the thread will be sharing a heap memory =
with the=20
            parent thread.<BR>In this case, memory allocation should be=20
            synchronized in their respective threads:<BR>RMutex=20
            sharedMutex;<BR>...<BR><BR>sharedMutex.Wait();<BR>array[i] =
=3D=20
            User::Alloc( bytesToAlloc=20
            );<BR>sharedMutex.Signal();<BR>sharedMutex.Wait();<BR>TInt =
heapSize=20
            =3D User::Available( largestBlock =
);<BR>sharedMutex.Signal();<BR>2)=20
            Dedicated heap:<BR>When the following overloaded version of=20
            RThread::Create() is used, the new thread will use its own=20
            independent heap.<BR>IMPORT_C TInt Create( const TDesC=20
            &amp;aName,<BR>TThreadFunction aFunction,<BR>TInt=20
            aStackSize,<BR>TInt aHeapMinSize,<BR>TInt =
aHeapMaxSize,<BR>TAny=20
            *aPtr,<BR>TOwnerType aType =3D EOwnerProcess );<BR>With =
separate=20
            heaps, the memory allocation calls do not have to be =
synchronized.=20
          =
</TD></TR></TBODY></TABLE></DIV>=E8=B0=A2=E8=B0=A2qxiaoyuan=E7=9A=84=E5=9B=
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      =
border=3D0>=EF=BC=8C=E6=88=91=E4=B9=8B=E6=89=80=E4=BB=A5=E4=BC=9A=E6=9C=89=
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      =
border=3D0>=EF=BC=8C=E4=B8=BA=E4=BB=80=E4=B9=88=E5=9C=A8=E5=88=86=E9=85=8D=
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f"=20
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      =
border=3D0>=EF=BC=8C=E6=89=80=E4=BB=A5=E6=89=8D=E5=8F=91=E8=BF=99=E4=B8=AA=
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=8D=E5=86=85=E5=AD=98=E4=B8=8D=E5=AE=89=E5=85=A8=EF=BC=8C=E5=A6=82=E6=9E=9C=
=E6=89=80=E6=9C=89=E7=9A=84=E5=88=86=E9=85=8D=E5=86=85=E5=AD=98=E9=83=BD=E9=
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      <DIV class=3Dspacer></DIV><EM>Last edited by tianciyixiao : =
2008-11-03 at=20
      <SPAN class=3Dtime>13:55</SPAN>. </EM></DIV><!-- / edit note -->
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