[M3devel] race conditions in lock-free code...

Tony Hosking hosking at cs.purdue.edu
Tue Aug 28 02:40:40 CEST 2012


On Intel we should be OK: x86-TSO causes the write to x^ to appear before the write to global on all cores.

Yes, I think it may have been problematic on Alpha and may still be on PowerPC.  To make the character write visible one would need a fence after the assignment to x^ before returning x.

It would be straightforward to fix this using a LOCK statement around the allocation and initialization.  Or alternatively, if we assume all constructors include an implicit fence then using a constructor would do the trick.

Antony Hosking | Associate Professor | Computer Science | Purdue University
305 N. University Street | West Lafayette | IN 47907 | USA
Mobile +1 765 427 5484





On Aug 27, 2012, at 2:34 PM, Mika Nystrom <mika at async.caltech.edu> wrote:

> 
> yeah I agree.
> 
> processor 1 performs...
> 
> x  := alloc_new_text
> x^ := character
> return x
> global := x
> 
> processor 2 performs
> 
> IF global # NIL THEN use(global) END 
> 
> now if out of all this, x^ := character is held back, e.g., in a processor
> write buffer, and if use(global) involves performing global^, the value
> of global^ will be the value of global^ just after x := alloc_new_text
> and before x^ := character.
> 
> I believe very aggressive architectures such as Alpha permit reordering
> to that extent.  If memory serves, on Alpha, if you do not perform a
> Memory Barrier, pretty much nothing can be inferred on one processor
> about the ordering of operations on another.
> 
> X86 I am not sure is that aggressive.  In a hardware-synchronized
> multiprocessor environment without barrier operations using e.g. the
> Illinois/MESI protocol (doesn't X86?), at the point x^ := character is
> performed, the cache coherence protocol has to guarantee the cache line
> is in state Exclusive, which means it has to be evicted from the cache
> in processor 2 and when use(global) comes around the protocol will
> have to ensure it is in Shared state on processor 2.  (Or Exclusive,
> if P1 writes it back and invalidates.)  This would guarantee that you
> could not actually see a very old value for global^ at the same time
> as a newer value for global.  The protocol guarantees that the relative
> ordering of writes is maintained across processors.
> 
> Of course I don't know whether Alphas are actually that aggressive in
> practice.  I'd suspect that a multiprocessor 21264 could be.  But I do
> agree it's a bug relative to the Alpha Architecture Manual.  A very nasty
> one at that.
> 
>    Mika
> 
> 
> Jay K writes:
>> --_5c33c9ca-3a7d-4c39-ab66-ab9c151d1539_
>> Content-Type: text/plain; charset="iso-8859-1"
>> Content-Transfer-Encoding: quoted-printable
>> 
>> It is NOT benign.
>> The global can be written before the initialization of what it points to is=
>> done.
>> The result is wrong.
>> 
>> 
>> It IS benign if multiple threads go and allocate separate multiple initiali=
>> zed TEXTs.
>> That's not the problem.
>> 
>> 
>> - Jay
>> 
>> 
>>> CC: jay.krell at cornell.edu=3B m3devel at elegosoft.com
>>> From: hosking at cs.purdue.edu
>>> Subject: Re: [M3devel] race conditions in lock-free code...
>>> Date: Mon=2C 27 Aug 2012 09:27:38 -0400
>>> To: mika at async.caltech.edu
>>> =20
>>> So why is this anything other than benign? It's a cache and there's no pr=
>> oblem if different threads get different texts. Don't cripple performance u=
>> nnecessarily.  The collector will reclaim any unreachable text.
>>> =20
>>> Sent from my iPad
>>> =20
>>> On Aug 27=2C 2012=2C at 3:17 AM=2C Mika Nystrom <mika at async.caltech.edu> =
>> wrote:
>>> =20
>>>> Oh I see now.
>>>> =20
>>>> It's not that the processor reorders in any tricky way.  It is that the
>>>> write performed by Text8.New could be sitting around processor 1's cach=
>> e
>>>> indefinitely without actually getting written back to main memory.
>>>> Processor 2 might see the new pointer=2C but when reading the memory po=
>> inted
>>>> to=2C would get uninitialized memory.  I think this can happen on Alpha=
>> but
>>>> maybe not X86 (without further reorderings anyhow)?
>>>> =20
>>>> Any chance any of the pthreads bugs could be of this nature?  How are t=
>> he
>>>> pthreads doing?  I gathered some bugs were fixed but I haven't tried th=
>> e
>>>> system for a while.
>>>> =20
>>>>    Mika
>>>> =20
>>>> =20
>>>> Jay K writes:
>>>>> --_86f22d85-5540-4565-bf73-232aaafdc94b_
>>>>> Content-Type: text/plain=3B charset=3D"iso-8859-1"
>>>>> Content-Transfer-Encoding: quoted-printable
>>>>> =20
>>>>> The processor can reorder. Across call/ret at least in general.
>>>>> =20
>>>>> =20
>>>>> The compiler can also reorder=3D2C if you have whole-program-optimizat=
>> ion=3D2C =3D
>>>>> link-time-code-gen (Microsoft "LTCG")=3D2C link-time-optimization (gcc=
>> "LTO")=3D
>>>>> . (We don't=3D2C but real world systems certainly do.)
>>>>> =20
>>>>> =20
>>>>> - Jay
>>>>> =20
>>>>> =20
>>>>>> To: jay.krell at cornell.edu=3D3B m3devel at elegosoft.com=3D3B mika at async.=
>> caltech.=3D
>>>>> edu
>>>>>> Subject: Re: [M3devel] race conditions in lock-free code...
>>>>>> Date: Sun=3D2C 26 Aug 2012 22:32:48 -0700
>>>>>> From: mika at async.caltech.edu
>>>>>> =3D20
>>>>>> Sorry=3D2C I can't seem to quote your message.
>>>>>> =3D20
>>>>>> You say that Text8.New's result can be assigned to fromCharCache[c]
>>>>>> before Text8.New is done running.  How is that possible?  Surely
>>>>>> Text8.New has to calculate its result before it can be assigned
>>>>>> anywhere.  Yes possibly FromChar allocates space for the result of
>>>>>> Text8.New but the assignment of whatever appears in that space can't
>>>>>> happen until *after* Text8.New has run.  Unless you are saying that
>>>>>> the running of Text8.New and FromChar are intertwined somehow..?
>>>>>> I know compilers do some odd things but that doesn't sound right...
>>>>>> =3D20
>>>>>> If Text8.New took fromCharCache[c] as a VAR parameter you might be
>>>>>> right=3D2C though.  But it doesn't...
>>>>>> =3D20
>>>>>> Am I missing something?
>>>>>> =3D20
>>>>>>    Mika
>>>>>> =3D20
>>>>>> Mika Nystrom writes:
>>>>>>> =20
>>>>>>> Yeah it's a race condition=3D2C in theory.  But is it important?  If=
>> you g=3D
>>>>> et
>>>>>>> the wrong copy=3D2C there will be two TEXTs representing one CHAR.  =
>> But no
>>>>>>> one ever said FromChar was guaranteed to return the same pointer whe=
>> n
>>>>>>> you call it with the same CHAR...
>>>>>>> =20
>>>>>>>   Mika
>>>>>>> =20
>>>>>>> Jay K writes:
>>>>>>>> --_5f23896e-68ee-44da-82dd-311cd8c58979_
>>>>>>>> Content-Type: text/plain=3D3B charset=3D3D"iso-8859-1"
>>>>>>>> Content-Transfer-Encoding: quoted-printable
>>>>>>>> =20
>>>>>>>> We have race conditions=3D3D2C like this=3D3D2C m3core/src/Text.m3:
>>>>>>>> =20
>>>>>>>> =20
>>>>>>>> VAR fromCharCache :=3D3D3D ARRAY CHAR OF T {NIL=3D3D2C ..}=3D3D3B (=
>> * 1-char t=3D
>>>>> exts *)
>>>>>>>> =20
>>>>>>>> =20
>>>>>>>> PROCEDURE FromChar (c: CHAR): T =3D3D3D
>>>>>>>> VAR buf: ARRAY [0..0] OF CHAR=3D3D3B
>>>>>>>> BEGIN
>>>>>>>>  IF fromCharCache [c] =3D3D3D NIL THEN
>>>>>>>>    buf [0] :=3D3D3D c=3D3D3B
>>>>>>>>    fromCharCache[c] :=3D3D3D Text8.New (buf)=3D3D3B
>>>>>>>>  END=3D3D3B
>>>>>>>>  RETURN fromCharCache [c]
>>>>>>>> END FromChar=3D3D3B
>>>>>>>> =20
>>>>>>>> =20
>>>>>>>> It should be:
>>>>>>>> =20
>>>>>>>> =20
>>>>>>>> PROCEDURE FromChar (c: CHAR): T =3D3D3D
>>>>>>>> =3D3D0A=3D3D
>>>>>>>> VAR buf: ARRAY [0..0] OF CHAR=3D3D3B
>>>>>>>> =3D3D0A=3D3D
>>>>>>>> BEGIN
>>>>>>>> =3D3D0A=3D3D
>>>>>>>>  IF fromCharCache [c] =3D3D3D NIL THEN
>>>>>>>> =3D3D0A=3D3D
>>>>>>>>    buf [0] :=3D3D3D c=3D3D3B
>>>>>>>> =3D3D0A=3D3D
>>>>>>>>    WITH a =3D3D3D Text8.New (buf) DO
>>>>>>>>      MemoryBarrier()=3D3D3B
>>>>>>>>      fromCharCache[c] :=3D3D3D a=3D3D3B
>>>>>>>>   END=3D3D3B
>>>>>>>> =3D3D0A=3D3D
>>>>>>>>  END=3D3D3B
>>>>>>>> =3D3D0A=3D3D
>>>>>>>>  RETURN fromCharCache [c]
>>>>>>>> =3D3D0A=3D3D
>>>>>>>> END FromChar=3D3D3B
>>>>>>>> =3D3D0A=3D3D
>>>>>>>> =20
>>>>>>>> =20
>>>>>>>> to ensure that all of Text8.New() finishes before the assignment to=
>> fro=3D
>>>>> mCha=3D3D
>>>>>>>> rCache[c] is made.
>>>>>>>> =20
>>>>>>>> =20
>>>>>>>> Can the compiler somehow catch these?
>>>>>>>> I fear they are a small epidemic.
>>>>>>>> For a long time people didn't realize where all the compiler and pr=
>> oces=3D
>>>>> sor =3D3D
>>>>>>>> could reorder.
>>>>>>>> =20
>>>>>>>> =20
>>>>>>>> Do we have the right constructs by now to fix them?
>>>>>>>> I think we do.
>>>>>>>> =20
>>>>>>>> =20
>>>>>>>> - Jay
>>>>>>>>                        =3D3D
>>>>>>>> =20
>>>>>>>> --_5f23896e-68ee-44da-82dd-311cd8c58979_
>>>>>>>> Content-Type: text/html=3D3B charset=3D3D"iso-8859-1"
>>>>>>>> Content-Transfer-Encoding: quoted-printable
>>>>>>>> =20
>>>>>>>> <html>
>>>>>>>> <head>
>>>>>>>> <style><!--
>>>>>>>> .hmmessage P
>>>>>>>> {
>>>>>>>> margin:0px=3D3D3B
>>>>>>>> padding:0px
>>>>>>>> }
>>>>>>>> body.hmmessage
>>>>>>>> {
>>>>>>>> font-size: 12pt=3D3D3B
>>>>>>>> font-family:Calibri
>>>>>>>> }
>>>>>>>> --></style></head>
>>>>>>>> <body class=3D3D3D'hmmessage'><div dir=3D3D3D'ltr'>We have race con=
>> ditions=3D
>>>>> =3D3D2C like =3D3D
>>>>>>>> this=3D3D2C m3core/src/Text.m3:<br><br><br>VAR fromCharCache :=3D3D=
>> 3D ARRAY=3D
>>>>> CHAR OF=3D3D
>>>>>>>> T {NIL=3D3D2C ..}=3D3D3B (* 1-char texts *)<br><br><br>PROCEDURE Fr=
>> omChar =3D
>>>>> (c: CHAR=3D3D
>>>>>>>> ): T =3D3D3D<br>&nbsp=3D3D3B VAR buf: ARRAY [0..0] OF CHAR=3D3D3B<b=
>> r>&nbsp=3D3D=3D
>>>>> 3B BEGIN<br>=3D3D
>>>>>>>> &nbsp=3D3D3B&nbsp=3D3D3B&nbsp=3D3D3B IF fromCharCache [c] =3D3D3D N=
>> IL THEN<br>&=3D
>>>>> nbsp=3D3D3B&nbsp=3D3D
>>>>>>>> =3D3D3B&nbsp=3D3D3B&nbsp=3D3D3B&nbsp=3D3D3B buf [0] :=3D3D3D c=3D3D=
>> 3B<br>&nbsp=3D3D3B=3D
>>>>> &nbsp=3D3D3B&nbsp=3D3D3B&n=3D3D
>>>>>>>> bsp=3D3D3B&nbsp=3D3D3B fromCharCache[c] :=3D3D3D Text8.New (buf)=3D=
>> 3D3B<br>&nbs=3D
>>>>> p=3D3D3B&nbsp=3D3D3B=3D3D
>>>>>>>> &nbsp=3D3D3B END=3D3D3B<br>&nbsp=3D3D3B&nbsp=3D3D3B&nbsp=3D3D3B RET=
>> URN fromCharCa=3D
>>>>> che [c]<br>&nb=3D3D
>>>>>>>> sp=3D3D3B END FromChar=3D3D3B<br><br><br>It should be:<br><br><br>P=
>> ROCEDURE=3D
>>>>> FromCha=3D3D
>>>>>>>> r (c: CHAR): T =3D3D3D<br>=3D3D0A=3D3D
>>>>>>>> &nbsp=3D3D3B VAR buf: ARRAY [0..0] OF CHAR=3D3D3B<br>=3D3D0A=3D3D
>>>>>>>> &nbsp=3D3D3B BEGIN<br>=3D3D0A=3D3D
>>>>>>>> &nbsp=3D3D3B&nbsp=3D3D3B&nbsp=3D3D3B IF fromCharCache [c] =3D3D3D N=
>> IL THEN<br>=3D
>>>>> =3D3D0A=3D3D
>>>>>>>> &nbsp=3D3D3B&nbsp=3D3D3B&nbsp=3D3D3B&nbsp=3D3D3B&nbsp=3D3D3B buf [0=
>> ] :=3D3D3D c=3D3D3=3D
>>>>> B<br>=3D3D0A=3D3D
>>>>>>>> &nbsp=3D3D3B&nbsp=3D3D3B&nbsp=3D3D3B&nbsp=3D3D3B&nbsp=3D3D3B WITH a=
>> =3D3D3D Text8.N=3D
>>>>> ew (buf) DO<br>&=3D3D
>>>>>>>> nbsp=3D3D3B&nbsp=3D3D3B&nbsp=3D3D3B&nbsp=3D3D3B&nbsp=3D3D3B&nbsp=3D=
>> 3D3B&nbsp=3D3D3B M=3D
>>>>> emoryBarrier()=3D3D3B<=3D3D
>>>>>>>> br>&nbsp=3D3D3B&nbsp=3D3D3B&nbsp=3D3D3B&nbsp=3D3D3B&nbsp=3D3D3B&nbs=
>> p=3D3D3B&nbsp=3D3D=3D
>>>>> 3B fromCharCache[c=3D3D
>>>>>>>> ] :=3D3D3D a=3D3D3B<br>&nbsp=3D3D3B&nbsp=3D3D3B&nbsp=3D3D3B&nbsp=3D=
>> 3D3B END=3D3D3B<br=3D
>>>>>> =3D3D0A=3D3D
>>>>>>>> &nbsp=3D3D3B&nbsp=3D3D3B&nbsp=3D3D3B END=3D3D3B<br>=3D3D0A=3D3D
>>>>>>>> &nbsp=3D3D3B&nbsp=3D3D3B&nbsp=3D3D3B RETURN fromCharCache [c]<br>=
>> =3D3D0A=3D3D
>>>>>>>> &nbsp=3D3D3B END FromChar=3D3D3B<br>=3D3D0A=3D3D
>>>>>>>> <br><br>to ensure that all of Text8.New() finishes before the assig=
>> nmen=3D
>>>>> t to=3D3D
>>>>>>>> fromCharCache[c] is made.<br><br><br>Can the compiler somehow catch=
>> th=3D
>>>>> ese?=3D3D
>>>>>>>> <br>I fear they are a small epidemic.<br>For a long time people did=
>> n't =3D
>>>>> real=3D3D
>>>>>>>> ize where all the compiler and processor could reorder.<br><br><br>=
>> Do w=3D
>>>>> e ha=3D3D
>>>>>>>> ve the right constructs by now to fix them?<br>I think we do.<br><b=
>> r><b=3D
>>>>> r> -=3D3D
>>>>>>>> Jay<br>                         </div></body>
>>>>>>>> </html>=3D3D
>>>>>>>> =20
>>>>>>>> --_5f23896e-68ee-44da-82dd-311cd8c58979_--
>>>>>                        =3D
>>>>> =20
>>>>> --_86f22d85-5540-4565-bf73-232aaafdc94b_
>>>>> Content-Type: text/html=3B charset=3D"iso-8859-1"
>>>>> Content-Transfer-Encoding: quoted-printable
>>>>> =20
>>>>> <html>
>>>>> <head>
>>>>> <style><!--
>>>>> .hmmessage P
>>>>> {
>>>>> margin:0px=3D3B
>>>>> padding:0px
>>>>> }
>>>>> body.hmmessage
>>>>> {
>>>>> font-size: 12pt=3D3B
>>>>> font-family:Calibri
>>>>> }
>>>>> --></style></head>
>>>>> <body class=3D3D'hmmessage'><div dir=3D3D'ltr'>The processor can reord=
>> er. Acros=3D
>>>>> s call/ret at least in general.<br><br><br>The compiler can also reord=
>> er=3D2C=3D
>>>>> if you have whole-program-optimization=3D2C link-time-code-gen (Micros=
>> oft "L=3D
>>>>> TCG")=3D2C link-time-optimization (gcc "LTO"). (We don't=3D2C but real=
>> world sy=3D
>>>>> stems certainly do.)<br><br><br>&nbsp=3D3B- Jay<br><br><br><div><div i=
>> d=3D3D"Sk=3D
>>>>> yDrivePlaceholder"></div>&gt=3D3B To: jay.krell at cornell.edu=3D3B m3dev=
>> el at elegos=3D
>>>>> oft.com=3D3B mika at async.caltech.edu<br>&gt=3D3B Subject: Re: [M3devel]=
>> race con=3D
>>>>> ditions in lock-free code...<br>&gt=3D3B Date: Sun=3D2C 26 Aug 2012 22=
>> :32:48 -0=3D
>>>>> 700<br>&gt=3D3B From: mika at async.caltech.edu<br>&gt=3D3B <br>&gt=3D3B =
>> Sorry=3D2C I =3D
>>>>> can't seem to quote your message.<br>&gt=3D3B <br>&gt=3D3B You say tha=
>> t Text8.N=3D
>>>>> ew's result can be assigned to fromCharCache[c]<br>&gt=3D3B before Tex=
>> t8.New =3D
>>>>> is done running.  How is that possible?  Surely<br>&gt=3D3B Text8.New =
>> has to =3D
>>>>> calculate its result before it can be assigned<br>&gt=3D3B anywhere.  =
>> Yes pos=3D
>>>>> sibly FromChar allocates space for the result of<br>&gt=3D3B Text8.New=
>> but th=3D
>>>>> e assignment of whatever appears in that space can't<br>&gt=3D3B happe=
>> n until=3D
>>>>> *after* Text8.New has run.  Unless you are saying that<br>&gt=3D3B the=
>> runni=3D
>>>>> ng of Text8.New and FromChar are intertwined somehow..?<br>&gt=3D3B I =
>> know co=3D
>>>>> mpilers do some odd things but that doesn't sound right...<br>&gt=3D3B=
>> <br>&g=3D
>>>>> t=3D3B If Text8.New took fromCharCache[c] as a VAR parameter you might=
>> be<br>=3D
>>>>> &gt=3D3B right=3D2C though.  But it doesn't...<br>&gt=3D3B <br>&gt=3D3=
>> B Am I missin=3D
>>>>> g something?<br>&gt=3D3B <br>&gt=3D3B      Mika<br>&gt=3D3B <br>&gt=3D=
>> 3B Mika Nystr=3D
>>>>> om writes:<br>&gt=3D3B &gt=3D3B<br>&gt=3D3B &gt=3D3BYeah it's a race c=
>> ondition=3D2C i=3D
>>>>> n theory.  But is it important?  If you get<br>&gt=3D3B &gt=3D3Bthe wr=
>> ong copy=3D
>>>>> =3D2C there will be two TEXTs representing one CHAR.  But no<br>&gt=3D=
>> 3B &gt=3D3B=3D
>>>>> one ever said FromChar was guaranteed to return the same pointer when<=
>> br>&g=3D
>>>>> t=3D3B &gt=3D3Byou call it with the same CHAR...<br>&gt=3D3B &gt=3D3B<=
>> br>&gt=3D3B &gt=3D
>>>>> =3D3B     Mika<br>&gt=3D3B &gt=3D3B<br>&gt=3D3B &gt=3D3BJay K writes:<=
>> br>&gt=3D3B &gt=3D
>>>>> =3D3B&gt=3D3B--_5f23896e-68ee-44da-82dd-311cd8c58979_<br>&gt=3D3B &gt=
>> =3D3B&gt=3D3BCon=3D
>>>>> tent-Type: text/plain=3D3B charset=3D3D"iso-8859-1"<br>&gt=3D3B &gt=3D=
>> 3B&gt=3D3BConte=3D
>>>>> nt-Transfer-Encoding: quoted-printable<br>&gt=3D3B &gt=3D3B&gt=3D3B<br=
>>> &gt=3D3B &gt=3D
>>>>> =3D3B&gt=3D3BWe have race conditions=3D3D2C like this=3D3D2C m3core/sr=
>> c/Text.m3:<br=3D
>>>>>> &gt=3D3B &gt=3D3B&gt=3D3B<br>&gt=3D3B &gt=3D3B&gt=3D3B<br>&gt=3D3B &g=
>> t=3D3B&gt=3D3BVAR fromC=3D
>>>>> harCache :=3D3D3D ARRAY CHAR OF T {NIL=3D3D2C ..}=3D3D3B (* 1-char tex=
>> ts *)<br>&g=3D
>>>>> t=3D3B &gt=3D3B&gt=3D3B<br>&gt=3D3B &gt=3D3B&gt=3D3B<br>&gt=3D3B &gt=
>> =3D3B&gt=3D3BPROCEDURE Fr=3D
>>>>> omChar (c: CHAR): T =3D3D3D<br>&gt=3D3B &gt=3D3B&gt=3D3B  VAR buf: ARR=
>> AY [0..0] OF =3D
>>>>> CHAR=3D3D3B<br>&gt=3D3B &gt=3D3B&gt=3D3B  BEGIN<br>&gt=3D3B &gt=3D3B&g=
>> t=3D3B    IF fromCh=3D
>>>>> arCache [c] =3D3D3D NIL THEN<br>&gt=3D3B &gt=3D3B&gt=3D3B      buf [0]=
>> :=3D3D3D c=3D3D3=3D
>>>>> B<br>&gt=3D3B &gt=3D3B&gt=3D3B      fromCharCache[c] :=3D3D3D Text8.Ne=
>> w (buf)=3D3D3B<=3D
>>>>> br>&gt=3D3B &gt=3D3B&gt=3D3B    END=3D3D3B<br>&gt=3D3B &gt=3D3B&gt=3D3=
>> B    RETURN fromCha=3D
>>>>> rCache [c]<br>&gt=3D3B &gt=3D3B&gt=3D3B  END FromChar=3D3D3B<br>&gt=3D=
>> 3B &gt=3D3B&gt=3D3B=3D
>>>>> <br>&gt=3D3B &gt=3D3B&gt=3D3B<br>&gt=3D3B &gt=3D3B&gt=3D3BIt should be=
>> :<br>&gt=3D3B &gt=3D
>>>>> =3D3B&gt=3D3B<br>&gt=3D3B &gt=3D3B&gt=3D3B<br>&gt=3D3B &gt=3D3B&gt=3D3=
>> BPROCEDURE FromChar (=3D
>>>>> c: CHAR): T =3D3D3D<br>&gt=3D3B &gt=3D3B&gt=3D3B=3D3D0A=3D3D<br>&gt=3D=
>> 3B &gt=3D3B&gt=3D3B  VA=3D
>>>>> R buf: ARRAY [0..0] OF CHAR=3D3D3B<br>&gt=3D3B &gt=3D3B&gt=3D3B=3D3D0A=
>> =3D3D<br>&gt=3D3B &=3D
>>>>> gt=3D3B&gt=3D3B  BEGIN<br>&gt=3D3B &gt=3D3B&gt=3D3B=3D3D0A=3D3D<br>&gt=
>> =3D3B &gt=3D3B&gt=3D3B   =3D
>>>>> IF fromCharCache [c] =3D3D3D NIL THEN<br>&gt=3D3B &gt=3D3B&gt=3D3B=3D3=
>> D0A=3D3D<br>&gt=3D
>>>>> =3D3B &gt=3D3B&gt=3D3B      buf [0] :=3D3D3D c=3D3D3B<br>&gt=3D3B &gt=
>> =3D3B&gt=3D3B=3D3D0A=3D3D<=3D
>>>>> br>&gt=3D3B &gt=3D3B&gt=3D3B      WITH a =3D3D3D Text8.New (buf) DO<br=
>>> &gt=3D3B &gt=3D
>>>>> =3D3B&gt=3D3B        MemoryBarrier()=3D3D3B<br>&gt=3D3B &gt=3D3B&gt=3D=
>> 3B        fromCha=3D
>>>>> rCache[c] :=3D3D3D a=3D3D3B<br>&gt=3D3B &gt=3D3B&gt=3D3B     END=3D3D3=
>> B<br>&gt=3D3B &gt=3D
>>>>> =3D3B&gt=3D3B=3D3D0A=3D3D<br>&gt=3D3B &gt=3D3B&gt=3D3B    END=3D3D3B<b=
>> r>&gt=3D3B &gt=3D3B&gt=3D3B=3D
>>>>> =3D3D0A=3D3D<br>&gt=3D3B &gt=3D3B&gt=3D3B    RETURN fromCharCache [c]<=
>> br>&gt=3D3B &gt=3D
>>>>> =3D3B&gt=3D3B=3D3D0A=3D3D<br>&gt=3D3B &gt=3D3B&gt=3D3B  END FromChar=
>> =3D3D3B<br>&gt=3D3B &gt=3D
>>>>> =3D3B&gt=3D3B=3D3D0A=3D3D<br>&gt=3D3B &gt=3D3B&gt=3D3B<br>&gt=3D3B &gt=
>> =3D3B&gt=3D3B<br>&gt=3D3B &=3D
>>>>> gt=3D3B&gt=3D3Bto ensure that all of Text8.New() finishes before the a=
>> ssignment=3D
>>>>> to fromCha=3D3D<br>&gt=3D3B &gt=3D3B&gt=3D3BrCache[c] is made.<br>&gt=
>> =3D3B &gt=3D3B&gt=3D
>>>>> =3D3B<br>&gt=3D3B &gt=3D3B&gt=3D3B<br>&gt=3D3B &gt=3D3B&gt=3D3BCan the=
>> compiler somehow c=3D
>>>>> atch these?<br>&gt=3D3B &gt=3D3B&gt=3D3BI fear they are a small epidem=
>> ic.<br>&gt=3D
>>>>> =3D3B &gt=3D3B&gt=3D3BFor a long time people didn't realize where all =
>> the compile=3D
>>>>> r and processor =3D3D<br>&gt=3D3B &gt=3D3B&gt=3D3Bcould reorder.<br>&g=
>> t=3D3B &gt=3D3B&g=3D
>>>>> t=3D3B<br>&gt=3D3B &gt=3D3B&gt=3D3B<br>&gt=3D3B &gt=3D3B&gt=3D3BDo we =
>> have the right cons=3D
>>>>> tructs by now to fix them?<br>&gt=3D3B &gt=3D3B&gt=3D3BI think we do.<=
>> br>&gt=3D3B &=3D
>>>>> gt=3D3B&gt=3D3B<br>&gt=3D3B &gt=3D3B&gt=3D3B<br>&gt=3D3B &gt=3D3B&gt=
>> =3D3B - Jay<br>&gt=3D3B &=3D
>>>>> gt=3D3B&gt=3D3B                         =3D3D<br>&gt=3D3B &gt=3D3B&gt=
>> =3D3B<br>&gt=3D3B &gt=3D3B&gt=3D3B--_=3D
>>>>> 5f23896e-68ee-44da-82dd-311cd8c58979_<br>&gt=3D3B &gt=3D3B&gt=3D3BCont=
>> ent-Type: t=3D
>>>>> ext/html=3D3B charset=3D3D"iso-8859-1"<br>&gt=3D3B &gt=3D3B&gt=3D3BCon=
>> tent-Transfer-E=3D
>>>>> ncoding: quoted-printable<br>&gt=3D3B &gt=3D3B&gt=3D3B<br>&gt=3D3B &gt=
>> =3D3B&gt=3D3B&lt=3D
>>>>> =3D3Bhtml&gt=3D3B<br>&gt=3D3B &gt=3D3B&gt=3D3B&lt=3D3Bhead&gt=3D3B<br>=
>> &gt=3D3B &gt=3D3B&gt=3D3B=3D
>>>>> &lt=3D3Bstyle&gt=3D3B&lt=3D3B!--<br>&gt=3D3B &gt=3D3B&gt=3D3B.hmmessag=
>> e P<br>&gt=3D3B &gt=3D
>>>>> =3D3B&gt=3D3B{<br>&gt=3D3B &gt=3D3B&gt=3D3Bmargin:0px=3D3D3B<br>&gt=3D=
>> 3B &gt=3D3B&gt=3D3Bpadd=3D
>>>>> ing:0px<br>&gt=3D3B &gt=3D3B&gt=3D3B}<br>&gt=3D3B &gt=3D3B&gt=3D3Bbody=
>> .hmmessage<br>&gt=3D
>>>>> =3D3B &gt=3D3B&gt=3D3B{<br>&gt=3D3B &gt=3D3B&gt=3D3Bfont-size: 12pt=3D=
>> 3D3B<br>&gt=3D3B &gt=3D
>>>>> =3D3B&gt=3D3Bfont-family:Calibri<br>&gt=3D3B &gt=3D3B&gt=3D3B}<br>&gt=
>> =3D3B &gt=3D3B&gt=3D3B=3D
>>>>> --&gt=3D3B&lt=3D3B/style&gt=3D3B&lt=3D3B/head&gt=3D3B<br>&gt=3D3B &gt=
>> =3D3B&gt=3D3B&lt=3D3Bbod=3D
>>>>> y class=3D3D3D'hmmessage'&gt=3D3B&lt=3D3Bdiv dir=3D3D3D'ltr'&gt=3D3BWe=
>> have race cond=3D
>>>>> itions=3D3D2C like =3D3D<br>&gt=3D3B &gt=3D3B&gt=3D3Bthis=3D3D2C m3cor=
>> e/src/Text.m3:&lt=3D
>>>>> =3D3Bbr&gt=3D3B&lt=3D3Bbr&gt=3D3B&lt=3D3Bbr&gt=3D3BVAR fromCharCache :=
>> =3D3D3D ARRAY CHAR =3D
>>>>> OF=3D3D<br>&gt=3D3B &gt=3D3B&gt=3D3B T {NIL=3D3D2C ..}=3D3D3B (* 1-cha=
>> r texts *)&lt=3D3Bb=3D
>>>>> r&gt=3D3B&lt=3D3Bbr&gt=3D3B&lt=3D3Bbr&gt=3D3BPROCEDURE FromChar (c: CH=
>> AR=3D3D<br>&gt=3D3B=3D
>>>>> &gt=3D3B&gt=3D3B): T =3D3D3D&lt=3D3Bbr&gt=3D3B&amp=3D3Bnbsp=3D3D3B VAR=
>> buf: ARRAY [0..0]=3D
>>>>> OF CHAR=3D3D3B&lt=3D3Bbr&gt=3D3B&amp=3D3Bnbsp=3D3D3B BEGIN&lt=3D3Bbr&g=
>> t=3D3B=3D3D<br>&gt=3D
>>>>> =3D3B &gt=3D3B&gt=3D3B&amp=3D3Bnbsp=3D3D3B&amp=3D3Bnbsp=3D3D3B&amp=3D3=
>> Bnbsp=3D3D3B IF fromCha=3D
>>>>> rCache [c] =3D3D3D NIL THEN&lt=3D3Bbr&gt=3D3B&amp=3D3Bnbsp=3D3D3B&amp=
>> =3D3Bnbsp=3D3D<br>&g=3D
>>>>> t=3D3B &gt=3D3B&gt=3D3B=3D3D3B&amp=3D3Bnbsp=3D3D3B&amp=3D3Bnbsp=3D3D3B=
>> &amp=3D3Bnbsp=3D3D3B buf =3D
>>>>> [0] :=3D3D3D c=3D3D3B&lt=3D3Bbr&gt=3D3B&amp=3D3Bnbsp=3D3D3B&amp=3D3Bnb=
>> sp=3D3D3B&amp=3D3Bnbsp=3D
>>>>> =3D3D3B&amp=3D3Bn=3D3D<br>&gt=3D3B &gt=3D3B&gt=3D3Bbsp=3D3D3B&amp=3D3B=
>> nbsp=3D3D3B fromCharCac=3D
>>>>> he[c] :=3D3D3D Text8.New (buf)=3D3D3B&lt=3D3Bbr&gt=3D3B&amp=3D3Bnbsp=
>> =3D3D3B&amp=3D3Bnbsp=3D
>>>>> =3D3D3B=3D3D<br>&gt=3D3B &gt=3D3B&gt=3D3B&amp=3D3Bnbsp=3D3D3B END=3D3D=
>> 3B&lt=3D3Bbr&gt=3D3B&amp=3D
>>>>> =3D3Bnbsp=3D3D3B&amp=3D3Bnbsp=3D3D3B&amp=3D3Bnbsp=3D3D3B RETURN fromCh=
>> arCache [c]&lt=3D3B=3D
>>>>> br&gt=3D3B&amp=3D3Bnb=3D3D<br>&gt=3D3B &gt=3D3B&gt=3D3Bsp=3D3D3B END F=
>> romChar=3D3D3B&lt=3D3Bb=3D
>>>>> r&gt=3D3B&lt=3D3Bbr&gt=3D3B&lt=3D3Bbr&gt=3D3BIt should be:&lt=3D3Bbr&g=
>> t=3D3B&lt=3D3Bbr&gt=3D
>>>>> =3D3B&lt=3D3Bbr&gt=3D3BPROCEDURE FromCha=3D3D<br>&gt=3D3B &gt=3D3B&gt=
>> =3D3Br (c: CHAR): T =3D
>>>>> =3D3D3D&lt=3D3Bbr&gt=3D3B=3D3D0A=3D3D<br>&gt=3D3B &gt=3D3B&gt=3D3B&amp=
>> =3D3Bnbsp=3D3D3B VAR buf:=3D
>>>>> ARRAY [0..0] OF CHAR=3D3D3B&lt=3D3Bbr&gt=3D3B=3D3D0A=3D3D<br>&gt=3D3B =
>> &gt=3D3B&gt=3D3B&amp=3D
>>>>> =3D3Bnbsp=3D3D3B BEGIN&lt=3D3Bbr&gt=3D3B=3D3D0A=3D3D<br>&gt=3D3B &gt=
>> =3D3B&gt=3D3B&amp=3D3Bnbsp=3D
>>>>> =3D3D3B&amp=3D3Bnbsp=3D3D3B&amp=3D3Bnbsp=3D3D3B IF fromCharCache [c] =
>> =3D3D3D NIL THEN&l=3D
>>>>> t=3D3Bbr&gt=3D3B=3D3D0A=3D3D<br>&gt=3D3B &gt=3D3B&gt=3D3B&amp=3D3Bnbsp=
>> =3D3D3B&amp=3D3Bnbsp=3D3D3B=3D
>>>>> &amp=3D3Bnbsp=3D3D3B&amp=3D3Bnbsp=3D3D3B&amp=3D3Bnbsp=3D3D3B buf [0] :=
>> =3D3D3D c=3D3D3B&lt=3D
>>>>> =3D3Bbr&gt=3D3B=3D3D0A=3D3D<br>&gt=3D3B &gt=3D3B&gt=3D3B&amp=3D3Bnbsp=
>> =3D3D3B&amp=3D3Bnbsp=3D3D3B&=3D
>>>>> amp=3D3Bnbsp=3D3D3B&amp=3D3Bnbsp=3D3D3B&amp=3D3Bnbsp=3D3D3B WITH a =3D=
>> 3D3D Text8.New (buf=3D
>>>>> ) DO&lt=3D3Bbr&gt=3D3B&amp=3D3B=3D3D<br>&gt=3D3B &gt=3D3B&gt=3D3Bnbsp=
>> =3D3D3B&amp=3D3Bnbsp=3D3D3=3D
>>>>> B&amp=3D3Bnbsp=3D3D3B&amp=3D3Bnbsp=3D3D3B&amp=3D3Bnbsp=3D3D3B&amp=3D3B=
>> nbsp=3D3D3B&amp=3D3Bnbs=3D
>>>>> p=3D3D3B MemoryBarrier()=3D3D3B&lt=3D3B=3D3D<br>&gt=3D3B &gt=3D3B&gt=
>> =3D3Bbr&gt=3D3B&amp=3D3Bn=3D
>>>>> bsp=3D3D3B&amp=3D3Bnbsp=3D3D3B&amp=3D3Bnbsp=3D3D3B&amp=3D3Bnbsp=3D3D3B=
>> &amp=3D3Bnbsp=3D3D3B&am=3D
>>>>> p=3D3Bnbsp=3D3D3B&amp=3D3Bnbsp=3D3D3B fromCharCache[c=3D3D<br>&gt=3D3B=
>> &gt=3D3B&gt=3D3B] :=3D
>>>>> =3D3D3D a=3D3D3B&lt=3D3Bbr&gt=3D3B&amp=3D3Bnbsp=3D3D3B&amp=3D3Bnbsp=3D=
>> 3D3B&amp=3D3Bnbsp=3D3D3B&=3D
>>>>> amp=3D3Bnbsp=3D3D3B END=3D3D3B&lt=3D3Bbr&gt=3D3B=3D3D0A=3D3D<br>&gt=3D=
>> 3B &gt=3D3B&gt=3D3B&amp=3D
>>>>> =3D3Bnbsp=3D3D3B&amp=3D3Bnbsp=3D3D3B&amp=3D3Bnbsp=3D3D3B END=3D3D3B&lt=
>> =3D3Bbr&gt=3D3B=3D3D0A=3D3D=3D
>>>>> <br>&gt=3D3B &gt=3D3B&gt=3D3B&amp=3D3Bnbsp=3D3D3B&amp=3D3Bnbsp=3D3D3B&=
>> amp=3D3Bnbsp=3D3D3B RET=3D
>>>>> URN fromCharCache [c]&lt=3D3Bbr&gt=3D3B=3D3D0A=3D3D<br>&gt=3D3B &gt=3D=
>> 3B&gt=3D3B&amp=3D3Bnb=3D
>>>>> sp=3D3D3B END FromChar=3D3D3B&lt=3D3Bbr&gt=3D3B=3D3D0A=3D3D<br>&gt=3D3=
>> B &gt=3D3B&gt=3D3B&lt=3D
>>>>> =3D3Bbr&gt=3D3B&lt=3D3Bbr&gt=3D3Bto ensure that all of Text8.New() fin=
>> ishes before =3D
>>>>> the assignment to=3D3D<br>&gt=3D3B &gt=3D3B&gt=3D3B fromCharCache[c] i=
>> s made.&lt=3D3B=3D
>>>>> br&gt=3D3B&lt=3D3Bbr&gt=3D3B&lt=3D3Bbr&gt=3D3BCan the compiler somehow=
>> catch these?=3D
>>>>> =3D3D<br>&gt=3D3B &gt=3D3B&gt=3D3B&lt=3D3Bbr&gt=3D3BI fear they are a =
>> small epidemic.&l=3D
>>>>> t=3D3Bbr&gt=3D3BFor a long time people didn't real=3D3D<br>&gt=3D3B &g=
>> t=3D3B&gt=3D3Bize=3D
>>>>> where all the compiler and processor could reorder.&lt=3D3Bbr&gt=3D3B&=
>> lt=3D3Bbr&=3D
>>>>> gt=3D3B&lt=3D3Bbr&gt=3D3BDo we ha=3D3D<br>&gt=3D3B &gt=3D3B&gt=3D3Bve =
>> the right construct=3D
>>>>> s by now to fix them?&lt=3D3Bbr&gt=3D3BI think we do.&lt=3D3Bbr&gt=3D3=
>> B&lt=3D3Bbr&gt=3D
>>>>> =3D3B&lt=3D3Bbr&gt=3D3B -=3D3D<br>&gt=3D3B &gt=3D3B&gt=3D3B Jay&lt=3D3=
>> Bbr&gt=3D3B                         =3D
>>>>> &lt=3D3B/div&gt=3D3B&lt=3D3B/body&gt=3D3B<br>&gt=3D3B &gt=3D3B&gt=3D3B=
>> &lt=3D3B/html&gt=3D3B=3D
>>>>> =3D3D<br>&gt=3D3B &gt=3D3B&gt=3D3B<br>&gt=3D3B &gt=3D3B&gt=3D3B--_5f23=
>> 896e-68ee-44da-82dd=3D
>>>>> -311cd8c58979_--<br></div>                         </div></body>
>>>>> </html>=3D
>>>>> =20
>>>>> --_86f22d85-5540-4565-bf73-232aaafdc94b_--
>> 		 	   		  =
>> 
>> --_5c33c9ca-3a7d-4c39-ab66-ab9c151d1539_
>> Content-Type: text/html; charset="iso-8859-1"
>> Content-Transfer-Encoding: quoted-printable
>> 
>> <html>
>> <head>
>> <style><!--
>> .hmmessage P
>> {
>> margin:0px=3B
>> padding:0px
>> }
>> body.hmmessage
>> {
>> font-size: 12pt=3B
>> font-family:Calibri
>> }
>> --></style></head>
>> <body class=3D'hmmessage'><div dir=3D'ltr'>It is NOT benign.<br>The global =
>> can be written before the initialization of what it points to is done.<br>T=
>> he result is wrong.<br><br><br>It IS benign if multiple threads go and allo=
>> cate separate multiple initialized TEXTs.<br>That's not the problem.<br><br=
>>> <br>&nbsp=3B- Jay<br><br><br><div><div id=3D"SkyDrivePlaceholder"></div>&g=
>> t=3B CC: jay.krell at cornell.edu=3B m3devel at elegosoft.com<br>&gt=3B From: hos=
>> king at cs.purdue.edu<br>&gt=3B Subject: Re: [M3devel] race conditions in lock=
>> -free code...<br>&gt=3B Date: Mon=2C 27 Aug 2012 09:27:38 -0400<br>&gt=3B T=
>> o: mika at async.caltech.edu<br>&gt=3B <br>&gt=3B So why is this anything othe=
>> r than benign? It's a cache and there's no problem if different threads get=
>> different texts. Don't cripple performance unnecessarily.  The collector w=
>> ill reclaim any unreachable text.<br>&gt=3B <br>&gt=3B Sent from my iPad<br=
>>> &gt=3B <br>&gt=3B On Aug 27=2C 2012=2C at 3:17 AM=2C Mika Nystrom &lt=3Bmi=
>> ka at async.caltech.edu&gt=3B wrote:<br>&gt=3B <br>&gt=3B &gt=3B Oh I see now.=
>> <br>&gt=3B &gt=3B <br>&gt=3B &gt=3B It's not that the processor reorders in=
>> any tricky way.  It is that the<br>&gt=3B &gt=3B write performed by Text8.=
>> New could be sitting around processor 1's cache<br>&gt=3B &gt=3B indefinite=
>> ly without actually getting written back to main memory.<br>&gt=3B &gt=3B P=
>> rocessor 2 might see the new pointer=2C but when reading the memory pointed=
>> <br>&gt=3B &gt=3B to=2C would get uninitialized memory.  I think this can h=
>> appen on Alpha but<br>&gt=3B &gt=3B maybe not X86 (without further reorderi=
>> ngs anyhow)?<br>&gt=3B &gt=3B <br>&gt=3B &gt=3B Any chance any of the pthre=
>> ads bugs could be of this nature?  How are the<br>&gt=3B &gt=3B pthreads do=
>> ing?  I gathered some bugs were fixed but I haven't tried the<br>&gt=3B &gt=
>> =3B system for a while.<br>&gt=3B &gt=3B <br>&gt=3B &gt=3B     Mika<br>&gt=
>> =3B &gt=3B <br>&gt=3B &gt=3B <br>&gt=3B &gt=3B Jay K writes:<br>&gt=3B &gt=
>> =3B&gt=3B --_86f22d85-5540-4565-bf73-232aaafdc94b_<br>&gt=3B &gt=3B&gt=3B C=
>> ontent-Type: text/plain=3B charset=3D"iso-8859-1"<br>&gt=3B &gt=3B&gt=3B Co=
>> ntent-Transfer-Encoding: quoted-printable<br>&gt=3B &gt=3B&gt=3B <br>&gt=3B=
>> &gt=3B&gt=3B The processor can reorder. Across call/ret at least in genera=
>> l.<br>&gt=3B &gt=3B&gt=3B <br>&gt=3B &gt=3B&gt=3B <br>&gt=3B &gt=3B&gt=3B T=
>> he compiler can also reorder=3D2C if you have whole-program-optimization=3D=
>> 2C =3D<br>&gt=3B &gt=3B&gt=3B link-time-code-gen (Microsoft "LTCG")=3D2C li=
>> nk-time-optimization (gcc "LTO")=3D<br>&gt=3B &gt=3B&gt=3B . (We don't=3D2C=
>> but real world systems certainly do.)<br>&gt=3B &gt=3B&gt=3B <br>&gt=3B &g=
>> t=3B&gt=3B <br>&gt=3B &gt=3B&gt=3B - Jay<br>&gt=3B &gt=3B&gt=3B <br>&gt=3B =
>> &gt=3B&gt=3B <br>&gt=3B &gt=3B&gt=3B&gt=3B To: jay.krell at cornell.edu=3D3B m=
>> 3devel at elegosoft.com=3D3B mika at async.caltech.=3D<br>&gt=3B &gt=3B&gt=3B edu=
>> <br>&gt=3B &gt=3B&gt=3B&gt=3B Subject: Re: [M3devel] race conditions in loc=
>> k-free code...<br>&gt=3B &gt=3B&gt=3B&gt=3B Date: Sun=3D2C 26 Aug 2012 22:3=
>> 2:48 -0700<br>&gt=3B &gt=3B&gt=3B&gt=3B From: mika at async.caltech.edu<br>&gt=
>> =3B &gt=3B&gt=3B&gt=3B =3D20<br>&gt=3B &gt=3B&gt=3B&gt=3B Sorry=3D2C I can'=
>> t seem to quote your message.<br>&gt=3B &gt=3B&gt=3B&gt=3B =3D20<br>&gt=3B =
>> &gt=3B&gt=3B&gt=3B You say that Text8.New's result can be assigned to fromC=
>> harCache[c]<br>&gt=3B &gt=3B&gt=3B&gt=3B before Text8.New is done running. =
>> How is that possible?  Surely<br>&gt=3B &gt=3B&gt=3B&gt=3B Text8.New has t=
>> o calculate its result before it can be assigned<br>&gt=3B &gt=3B&gt=3B&gt=
>> =3B anywhere.  Yes possibly FromChar allocates space for the result of<br>&=
>> gt=3B &gt=3B&gt=3B&gt=3B Text8.New but the assignment of whatever appears i=
>> n that space can't<br>&gt=3B &gt=3B&gt=3B&gt=3B happen until *after* Text8.=
>> New has run.  Unless you are saying that<br>&gt=3B &gt=3B&gt=3B&gt=3B the r=
>> unning of Text8.New and FromChar are intertwined somehow..?<br>&gt=3B &gt=
>> =3B&gt=3B&gt=3B I know compilers do some odd things but that doesn't sound =
>> right...<br>&gt=3B &gt=3B&gt=3B&gt=3B =3D20<br>&gt=3B &gt=3B&gt=3B&gt=3B If=
>> Text8.New took fromCharCache[c] as a VAR parameter you might be<br>&gt=3B =
>> &gt=3B&gt=3B&gt=3B right=3D2C though.  But it doesn't...<br>&gt=3B &gt=3B&g=
>> t=3B&gt=3B =3D20<br>&gt=3B &gt=3B&gt=3B&gt=3B Am I missing something?<br>&g=
>> t=3B &gt=3B&gt=3B&gt=3B =3D20<br>&gt=3B &gt=3B&gt=3B&gt=3B     Mika<br>&gt=
>> =3B &gt=3B&gt=3B&gt=3B =3D20<br>&gt=3B &gt=3B&gt=3B&gt=3B Mika Nystrom writ=
>> es:<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B <br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B =
>> Yeah it's a race condition=3D2C in theory.  But is it important?  If you g=
>> =3D<br>&gt=3B &gt=3B&gt=3B et<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B the wrong =
>> copy=3D2C there will be two TEXTs representing one CHAR.  But no<br>&gt=3B =
>> &gt=3B&gt=3B&gt=3B&gt=3B one ever said FromChar was guaranteed to return th=
>> e same pointer when<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B you call it with the=
>> same CHAR...<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B <br>&gt=3B &gt=3B&gt=3B&gt=
>> =3B&gt=3B    Mika<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B <br>&gt=3B &gt=3B&gt=
>> =3B&gt=3B&gt=3B Jay K writes:<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B --_5=
>> f23896e-68ee-44da-82dd-311cd8c58979_<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=
>> =3B Content-Type: text/plain=3D3B charset=3D3D"iso-8859-1"<br>&gt=3B &gt=3B=
>> &gt=3B&gt=3B&gt=3B&gt=3B Content-Transfer-Encoding: quoted-printable<br>&gt=
>> =3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B <br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=
>> =3B We have race conditions=3D3D2C like this=3D3D2C m3core/src/Text.m3:<br>=
>> &gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B <br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&g=
>> t=3B <br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B VAR fromCharCache :=3D3D3D A=
>> RRAY CHAR OF T {NIL=3D3D2C ..}=3D3D3B (* 1-char t=3D<br>&gt=3B &gt=3B&gt=3B=
>> exts *)<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B <br>&gt=3B &gt=3B&gt=3B&g=
>> t=3B&gt=3B&gt=3B <br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B PROCEDURE FromCh=
>> ar (c: CHAR): T =3D3D3D<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B VAR buf: A=
>> RRAY [0..0] OF CHAR=3D3D3B<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B BEGIN<b=
>> r>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B   IF fromCharCache [c] =3D3D3D NIL =
>> THEN<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B     buf [0] :=3D3D3D c=3D3D3B=
>> <br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B     fromCharCache[c] :=3D3D3D Tex=
>> t8.New (buf)=3D3D3B<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B   END=3D3D3B<b=
>> r>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B   RETURN fromCharCache [c]<br>&gt=
>> =3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B END FromChar=3D3D3B<br>&gt=3B &gt=3B&gt=
>> =3B&gt=3B&gt=3B&gt=3B <br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B <br>&gt=3B =
>> &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B It should be:<br>&gt=3B &gt=3B&gt=3B&gt=3B&g=
>> t=3B&gt=3B <br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B <br>&gt=3B &gt=3B&gt=
>> =3B&gt=3B&gt=3B&gt=3B PROCEDURE FromChar (c: CHAR): T =3D3D3D<br>&gt=3B &gt=
>> =3B&gt=3B&gt=3B&gt=3B&gt=3B =3D3D0A=3D3D<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B=
>> &gt=3B VAR buf: ARRAY [0..0] OF CHAR=3D3D3B<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=
>> =3B&gt=3B =3D3D0A=3D3D<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B BEGIN<br>&g=
>> t=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B =3D3D0A=3D3D<br>&gt=3B &gt=3B&gt=3B&gt=
>> =3B&gt=3B&gt=3B   IF fromCharCache [c] =3D3D3D NIL THEN<br>&gt=3B &gt=3B&gt=
>> =3B&gt=3B&gt=3B&gt=3B =3D3D0A=3D3D<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B=
>>    buf [0] :=3D3D3D c=3D3D3B<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B =3D=
>> 3D0A=3D3D<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B     WITH a =3D3D3D Text8=
>> .New (buf) DO<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B       MemoryBarrier(=
>> )=3D3D3B<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B       fromCharCache[c] :=
>> =3D3D3D a=3D3D3B<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B    END=3D3D3B<br>=
>> &gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B =3D3D0A=3D3D<br>&gt=3B &gt=3B&gt=3B&g=
>> t=3B&gt=3B&gt=3B   END=3D3D3B<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B =3D3=
>> D0A=3D3D<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B   RETURN fromCharCache [c=
>> ]<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B =3D3D0A=3D3D<br>&gt=3B &gt=3B&gt=
>> =3B&gt=3B&gt=3B&gt=3B END FromChar=3D3D3B<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=
>> =3B&gt=3B =3D3D0A=3D3D<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B <br>&gt=3B =
>> &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B <br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B to=
>> ensure that all of Text8.New() finishes before the assignment to fro=3D<br=
>>> &gt=3B &gt=3B&gt=3B mCha=3D3D<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B rCa=
>> che[c] is made.<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B <br>&gt=3B &gt=3B&=
>> gt=3B&gt=3B&gt=3B&gt=3B <br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B Can the c=
>> ompiler somehow catch these?<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B I fea=
>> r they are a small epidemic.<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B For a=
>> long time people didn't realize where all the compiler and proces=3D<br>&g=
>> t=3B &gt=3B&gt=3B sor =3D3D<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B could =
>> reorder.<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B <br>&gt=3B &gt=3B&gt=3B&g=
>> t=3B&gt=3B&gt=3B <br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B Do we have the r=
>> ight constructs by now to fix them?<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=
>> =3B I think we do.<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B <br>&gt=3B &gt=
>> =3B&gt=3B&gt=3B&gt=3B&gt=3B <br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B - Jay=
>> <br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B                         =3D3D<br>=
>> &gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B <br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&g=
>> t=3B --_5f23896e-68ee-44da-82dd-311cd8c58979_<br>&gt=3B &gt=3B&gt=3B&gt=3B&=
>> gt=3B&gt=3B Content-Type: text/html=3D3B charset=3D3D"iso-8859-1"<br>&gt=3B=
>> &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B Content-Transfer-Encoding: quoted-printable=
>> <br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B <br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=
>> =3B&gt=3B &lt=3Bhtml&gt=3B<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B &lt=3Bh=
>> ead&gt=3B<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B &lt=3Bstyle&gt=3B&lt=3B!=
>> --<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B .hmmessage P<br>&gt=3B &gt=3B&g=
>> t=3B&gt=3B&gt=3B&gt=3B {<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B margin:0p=
>> x=3D3D3B<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B padding:0px<br>&gt=3B &gt=
>> =3B&gt=3B&gt=3B&gt=3B&gt=3B }<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B body=
>> .hmmessage<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B {<br>&gt=3B &gt=3B&gt=
>> =3B&gt=3B&gt=3B&gt=3B font-size: 12pt=3D3D3B<br>&gt=3B &gt=3B&gt=3B&gt=3B&g=
>> t=3B&gt=3B font-family:Calibri<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B }<b=
>> r>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B --&gt=3B&lt=3B/style&gt=3B&lt=3B/he=
>> ad&gt=3B<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B &lt=3Bbody class=3D3D3D'h=
>> mmessage'&gt=3B&lt=3Bdiv dir=3D3D3D'ltr'&gt=3BWe have race conditions=3D<br=
>>> &gt=3B &gt=3B&gt=3B =3D3D2C like =3D3D<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&=
>> gt=3B this=3D3D2C m3core/src/Text.m3:&lt=3Bbr&gt=3B&lt=3Bbr&gt=3B&lt=3Bbr&g=
>> t=3BVAR fromCharCache :=3D3D3D ARRAY=3D<br>&gt=3B &gt=3B&gt=3B CHAR OF=3D3D=
>> <br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B T {NIL=3D3D2C ..}=3D3D3B (* 1-cha=
>> r texts *)&lt=3Bbr&gt=3B&lt=3Bbr&gt=3B&lt=3Bbr&gt=3BPROCEDURE FromChar =3D<=
>> br>&gt=3B &gt=3B&gt=3B (c: CHAR=3D3D<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=
>> =3B ): T =3D3D3D&lt=3Bbr&gt=3B&amp=3Bnbsp=3D3D3B VAR buf: ARRAY [0..0] OF C=
>> HAR=3D3D3B&lt=3Bbr&gt=3B&amp=3Bnbsp=3D3D=3D<br>&gt=3B &gt=3B&gt=3B 3B BEGIN=
>> &lt=3Bbr&gt=3B=3D3D<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B &amp=3Bnbsp=3D=
>> 3D3B&amp=3Bnbsp=3D3D3B&amp=3Bnbsp=3D3D3B IF fromCharCache [c] =3D3D3D NIL T=
>> HEN&lt=3Bbr&gt=3B&amp=3B=3D<br>&gt=3B &gt=3B&gt=3B nbsp=3D3D3B&amp=3Bnbsp=
>> =3D3D<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B =3D3D3B&amp=3Bnbsp=3D3D3B&am=
>> p=3Bnbsp=3D3D3B&amp=3Bnbsp=3D3D3B buf [0] :=3D3D3D c=3D3D3B&lt=3Bbr&gt=3B&a=
>> mp=3Bnbsp=3D3D3B=3D<br>&gt=3B &gt=3B&gt=3B &amp=3Bnbsp=3D3D3B&amp=3Bnbsp=3D=
>> 3D3B&amp=3Bn=3D3D<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B bsp=3D3D3B&amp=
>> =3Bnbsp=3D3D3B fromCharCache[c] :=3D3D3D Text8.New (buf)=3D3D3B&lt=3Bbr&gt=
>> =3B&amp=3Bnbs=3D<br>&gt=3B &gt=3B&gt=3B p=3D3D3B&amp=3Bnbsp=3D3D3B=3D3D<br>=
>> &gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B &amp=3Bnbsp=3D3D3B END=3D3D3B&lt=3Bbr=
>> &gt=3B&amp=3Bnbsp=3D3D3B&amp=3Bnbsp=3D3D3B&amp=3Bnbsp=3D3D3B RETURN fromCha=
>> rCa=3D<br>&gt=3B &gt=3B&gt=3B che [c]&lt=3Bbr&gt=3B&amp=3Bnb=3D3D<br>&gt=3B=
>> &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B sp=3D3D3B END FromChar=3D3D3B&lt=3Bbr&gt=3B=
>> &lt=3Bbr&gt=3B&lt=3Bbr&gt=3BIt should be:&lt=3Bbr&gt=3B&lt=3Bbr&gt=3B&lt=3B=
>> br&gt=3BPROCEDURE=3D<br>&gt=3B &gt=3B&gt=3B FromCha=3D3D<br>&gt=3B &gt=3B&g=
>> t=3B&gt=3B&gt=3B&gt=3B r (c: CHAR): T =3D3D3D&lt=3Bbr&gt=3B=3D3D0A=3D3D<br>=
>> &gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B &amp=3Bnbsp=3D3D3B VAR buf: ARRAY [0.=
>> .0] OF CHAR=3D3D3B&lt=3Bbr&gt=3B=3D3D0A=3D3D<br>&gt=3B &gt=3B&gt=3B&gt=3B&g=
>> t=3B&gt=3B &amp=3Bnbsp=3D3D3B BEGIN&lt=3Bbr&gt=3B=3D3D0A=3D3D<br>&gt=3B &gt=
>> =3B&gt=3B&gt=3B&gt=3B&gt=3B &amp=3Bnbsp=3D3D3B&amp=3Bnbsp=3D3D3B&amp=3Bnbsp=
>> =3D3D3B IF fromCharCache [c] =3D3D3D NIL THEN&lt=3Bbr&gt=3B=3D<br>&gt=3B &g=
>> t=3B&gt=3B =3D3D0A=3D3D<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B &amp=3Bnbs=
>> p=3D3D3B&amp=3Bnbsp=3D3D3B&amp=3Bnbsp=3D3D3B&amp=3Bnbsp=3D3D3B&amp=3Bnbsp=
>> =3D3D3B buf [0] :=3D3D3D c=3D3D3=3D<br>&gt=3B &gt=3B&gt=3B B&lt=3Bbr&gt=3B=
>> =3D3D0A=3D3D<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B &amp=3Bnbsp=3D3D3B&am=
>> p=3Bnbsp=3D3D3B&amp=3Bnbsp=3D3D3B&amp=3Bnbsp=3D3D3B&amp=3Bnbsp=3D3D3B WITH =
>> a =3D3D3D Text8.N=3D<br>&gt=3B &gt=3B&gt=3B ew (buf) DO&lt=3Bbr&gt=3B&amp=
>> =3B=3D3D<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B nbsp=3D3D3B&amp=3Bnbsp=3D=
>> 3D3B&amp=3Bnbsp=3D3D3B&amp=3Bnbsp=3D3D3B&amp=3Bnbsp=3D3D3B&amp=3Bnbsp=3D3D3=
>> B&amp=3Bnbsp=3D3D3B M=3D<br>&gt=3B &gt=3B&gt=3B emoryBarrier()=3D3D3B&lt=3B=
>> =3D3D<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B br&gt=3B&amp=3Bnbsp=3D3D3B&a=
>> mp=3Bnbsp=3D3D3B&amp=3Bnbsp=3D3D3B&amp=3Bnbsp=3D3D3B&amp=3Bnbsp=3D3D3B&amp=
>> =3Bnbsp=3D3D3B&amp=3Bnbsp=3D3D=3D<br>&gt=3B &gt=3B&gt=3B 3B fromCharCache[c=
>> =3D3D<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B ] :=3D3D3D a=3D3D3B&lt=3Bbr&=
>> gt=3B&amp=3Bnbsp=3D3D3B&amp=3Bnbsp=3D3D3B&amp=3Bnbsp=3D3D3B&amp=3Bnbsp=3D3D=
>> 3B END=3D3D3B&lt=3Bbr=3D<br>&gt=3B &gt=3B&gt=3B&gt=3B =3D3D0A=3D3D<br>&gt=
>> =3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B &amp=3Bnbsp=3D3D3B&amp=3Bnbsp=3D3D3B&amp=
>> =3Bnbsp=3D3D3B END=3D3D3B&lt=3Bbr&gt=3B=3D3D0A=3D3D<br>&gt=3B &gt=3B&gt=3B&=
>> gt=3B&gt=3B&gt=3B &amp=3Bnbsp=3D3D3B&amp=3Bnbsp=3D3D3B&amp=3Bnbsp=3D3D3B RE=
>> TURN fromCharCache [c]&lt=3Bbr&gt=3B=3D3D0A=3D3D<br>&gt=3B &gt=3B&gt=3B&gt=
>> =3B&gt=3B&gt=3B &amp=3Bnbsp=3D3D3B END FromChar=3D3D3B&lt=3Bbr&gt=3B=3D3D0A=
>> =3D3D<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B &lt=3Bbr&gt=3B&lt=3Bbr&gt=3B=
>> to ensure that all of Text8.New() finishes before the assignmen=3D<br>&gt=
>> =3B &gt=3B&gt=3B t to=3D3D<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B fromCha=
>> rCache[c] is made.&lt=3Bbr&gt=3B&lt=3Bbr&gt=3B&lt=3Bbr&gt=3BCan the compile=
>> r somehow catch th=3D<br>&gt=3B &gt=3B&gt=3B ese?=3D3D<br>&gt=3B &gt=3B&gt=
>> =3B&gt=3B&gt=3B&gt=3B &lt=3Bbr&gt=3BI fear they are a small epidemic.&lt=3B=
>> br&gt=3BFor a long time people didn't =3D<br>&gt=3B &gt=3B&gt=3B real=3D3D<=
>> br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B ize where all the compiler and pro=
>> cessor could reorder.&lt=3Bbr&gt=3B&lt=3Bbr&gt=3B&lt=3Bbr&gt=3BDo w=3D<br>&=
>> gt=3B &gt=3B&gt=3B e ha=3D3D<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B ve th=
>> e right constructs by now to fix them?&lt=3Bbr&gt=3BI think we do.&lt=3Bbr&=
>> gt=3B&lt=3Bbr&gt=3B&lt=3Bb=3D<br>&gt=3B &gt=3B&gt=3B r&gt=3B -=3D3D<br>&gt=
>> =3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B Jay&lt=3Bbr&gt=3B                       =
>> &lt=3B/div&gt=3B&lt=3B/body&gt=3B<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=
>> =3B &lt=3B/html&gt=3B=3D3D<br>&gt=3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B <br>&gt=
>> =3B &gt=3B&gt=3B&gt=3B&gt=3B&gt=3B --_5f23896e-68ee-44da-82dd-311cd8c58979_=
>> --<br>&gt=3B &gt=3B&gt=3B                         =3D<br>&gt=3B &gt=3B&gt=
>> =3B <br>&gt=3B &gt=3B&gt=3B --_86f22d85-5540-4565-bf73-232aaafdc94b_<br>&gt=
>> =3B &gt=3B&gt=3B Content-Type: text/html=3B charset=3D"iso-8859-1"<br>&gt=
>> =3B &gt=3B&gt=3B Content-Transfer-Encoding: quoted-printable<br>&gt=3B &gt=
>> =3B&gt=3B <br>&gt=3B &gt=3B&gt=3B &lt=3Bhtml&gt=3B<br>&gt=3B &gt=3B&gt=3B &=
>> lt=3Bhead&gt=3B<br>&gt=3B &gt=3B&gt=3B &lt=3Bstyle&gt=3B&lt=3B!--<br>&gt=3B=
>> &gt=3B&gt=3B .hmmessage P<br>&gt=3B &gt=3B&gt=3B {<br>&gt=3B &gt=3B&gt=3B =
>> margin:0px=3D3B<br>&gt=3B &gt=3B&gt=3B padding:0px<br>&gt=3B &gt=3B&gt=3B }=
>> <br>&gt=3B &gt=3B&gt=3B body.hmmessage<br>&gt=3B &gt=3B&gt=3B {<br>&gt=3B &=
>> gt=3B&gt=3B font-size: 12pt=3D3B<br>&gt=3B &gt=3B&gt=3B font-family:Calibri=
>> <br>&gt=3B &gt=3B&gt=3B }<br>&gt=3B &gt=3B&gt=3B --&gt=3B&lt=3B/style&gt=3B=
>> &lt=3B/head&gt=3B<br>&gt=3B &gt=3B&gt=3B &lt=3Bbody class=3D3D'hmmessage'&g=
>> t=3B&lt=3Bdiv dir=3D3D'ltr'&gt=3BThe processor can reorder. Acros=3D<br>&gt=
>> =3B &gt=3B&gt=3B s call/ret at least in general.&lt=3Bbr&gt=3B&lt=3Bbr&gt=
>> =3B&lt=3Bbr&gt=3BThe compiler can also reorder=3D2C=3D<br>&gt=3B &gt=3B&gt=
>> =3B if you have whole-program-optimization=3D2C link-time-code-gen (Microso=
>> ft "L=3D<br>&gt=3B &gt=3B&gt=3B TCG")=3D2C link-time-optimization (gcc "LTO=
>> "). (We don't=3D2C but real world sy=3D<br>&gt=3B &gt=3B&gt=3B stems certai=
>> nly do.)&lt=3Bbr&gt=3B&lt=3Bbr&gt=3B&lt=3Bbr&gt=3B&amp=3Bnbsp=3D3B- Jay&lt=
>> =3Bbr&gt=3B&lt=3Bbr&gt=3B&lt=3Bbr&gt=3B&lt=3Bdiv&gt=3B&lt=3Bdiv id=3D3D"Sk=
>> =3D<br>&gt=3B &gt=3B&gt=3B yDrivePlaceholder"&gt=3B&lt=3B/div&gt=3B&amp=3Bg=
>> t=3D3B To: jay.krell at cornell.edu=3D3B m3devel at elegos=3D<br>&gt=3B &gt=3B&gt=
>> =3B oft.com=3D3B mika at async.caltech.edu&lt=3Bbr&gt=3B&amp=3Bgt=3D3B Subject=
>> : Re: [M3devel] race con=3D<br>&gt=3B &gt=3B&gt=3B ditions in lock-free cod=
>> e...&lt=3Bbr&gt=3B&amp=3Bgt=3D3B Date: Sun=3D2C 26 Aug 2012 22:32:48 -0=3D<=
>> br>&gt=3B &gt=3B&gt=3B 700&lt=3Bbr&gt=3B&amp=3Bgt=3D3B From: mika at async.cal=
>> tech.edu&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &lt=3Bbr&gt=3B&amp=3Bgt=3D3B Sorry=3D2=
>> C I =3D<br>&gt=3B &gt=3B&gt=3B can't seem to quote your message.&lt=3Bbr&gt=
>> =3B&amp=3Bgt=3D3B &lt=3Bbr&gt=3B&amp=3Bgt=3D3B You say that Text8.N=3D<br>&=
>> gt=3B &gt=3B&gt=3B ew's result can be assigned to fromCharCache[c]&lt=3Bbr&=
>> gt=3B&amp=3Bgt=3D3B before Text8.New =3D<br>&gt=3B &gt=3B&gt=3B is done run=
>> ning.  How is that possible?  Surely&lt=3Bbr&gt=3B&amp=3Bgt=3D3B Text8.New =
>> has to =3D<br>&gt=3B &gt=3B&gt=3B calculate its result before it can be ass=
>> igned&lt=3Bbr&gt=3B&amp=3Bgt=3D3B anywhere.  Yes pos=3D<br>&gt=3B &gt=3B&gt=
>> =3B sibly FromChar allocates space for the result of&lt=3Bbr&gt=3B&amp=3Bgt=
>> =3D3B Text8.New but th=3D<br>&gt=3B &gt=3B&gt=3B e assignment of whatever a=
>> ppears in that space can't&lt=3Bbr&gt=3B&amp=3Bgt=3D3B happen until=3D<br>&=
>> gt=3B &gt=3B&gt=3B *after* Text8.New has run.  Unless you are saying that&l=
>> t=3Bbr&gt=3B&amp=3Bgt=3D3B the runni=3D<br>&gt=3B &gt=3B&gt=3B ng of Text8.=
>> New and FromChar are intertwined somehow..?&lt=3Bbr&gt=3B&amp=3Bgt=3D3B I k=
>> now co=3D<br>&gt=3B &gt=3B&gt=3B mpilers do some odd things but that doesn'=
>> t sound right...&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &lt=3Bbr&gt=3B&amp=3Bg=3D<br>&=
>> gt=3B &gt=3B&gt=3B t=3D3B If Text8.New took fromCharCache[c] as a VAR param=
>> eter you might be&lt=3Bbr&gt=3B=3D<br>&gt=3B &gt=3B&gt=3B &amp=3Bgt=3D3B ri=
>> ght=3D2C though.  But it doesn't...&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &lt=3Bbr&gt=
>> =3B&amp=3Bgt=3D3B Am I missin=3D<br>&gt=3B &gt=3B&gt=3B g something?&lt=3Bb=
>> r&gt=3B&amp=3Bgt=3D3B &lt=3Bbr&gt=3B&amp=3Bgt=3D3B      Mika&lt=3Bbr&gt=3B&=
>> amp=3Bgt=3D3B &lt=3Bbr&gt=3B&amp=3Bgt=3D3B Mika Nystr=3D<br>&gt=3B &gt=3B&g=
>> t=3B om writes:&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&lt=3Bbr&gt=3B&am=
>> p=3Bgt=3D3B &amp=3Bgt=3D3BYeah it's a race condition=3D2C i=3D<br>&gt=3B &g=
>> t=3B&gt=3B n theory.  But is it important?  If you get&lt=3Bbr&gt=3B&amp=3B=
>> gt=3D3B &amp=3Bgt=3D3Bthe wrong copy=3D<br>&gt=3B &gt=3B&gt=3B =3D2C there =
>> will be two TEXTs representing one CHAR.  But no&lt=3Bbr&gt=3B&amp=3Bgt=3D3=
>> B &amp=3Bgt=3D3B=3D<br>&gt=3B &gt=3B&gt=3B one ever said FromChar was guara=
>> nteed to return the same pointer when&lt=3Bbr&gt=3B&amp=3Bg=3D<br>&gt=3B &g=
>> t=3B&gt=3B t=3D3B &amp=3Bgt=3D3Byou call it with the same CHAR...&lt=3Bbr&g=
>> t=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D<=
>> br>&gt=3B &gt=3B&gt=3B =3D3B     Mika&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=
>> =3D3B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3BJay K writes:&lt=3Bbr&gt=3B=
>> &amp=3Bgt=3D3B &amp=3Bgt=3D<br>&gt=3B &gt=3B&gt=3B =3D3B&amp=3Bgt=3D3B--_5f=
>> 23896e-68ee-44da-82dd-311cd8c58979_&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=
>> =3D3B&amp=3Bgt=3D3BCon=3D<br>&gt=3B &gt=3B&gt=3B tent-Type: text/plain=3D3B=
>> charset=3D3D"iso-8859-1"&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3B=
>> gt=3D3BConte=3D<br>&gt=3B &gt=3B&gt=3B nt-Transfer-Encoding: quoted-printab=
>> le&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B&lt=3Bbr&gt=3B&a=
>> mp=3Bgt=3D3B &amp=3Bgt=3D<br>&gt=3B &gt=3B&gt=3B =3D3B&amp=3Bgt=3D3BWe have=
>> race conditions=3D3D2C like this=3D3D2C m3core/src/Text.m3:&lt=3Bbr=3D<br>=
>> &gt=3B &gt=3B&gt=3B&gt=3B &amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B&lt=3B=
>> br&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B&lt=3Bbr&gt=3B&amp=3Bgt=
>> =3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3BVAR fromC=3D<br>&gt=3B &gt=3B&gt=3B harCa=
>> che :=3D3D3D ARRAY CHAR OF T {NIL=3D3D2C ..}=3D3D3B (* 1-char texts *)&lt=
>> =3Bbr&gt=3B&amp=3Bg=3D<br>&gt=3B &gt=3B&gt=3B t=3D3B &amp=3Bgt=3D3B&amp=3Bg=
>> t=3D3B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B&lt=3Bbr&gt=
>> =3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3BPROCEDURE Fr=3D<br>&gt=3B &gt=
>> =3B&gt=3B omChar (c: CHAR): T =3D3D3D&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=
>> =3D3B&amp=3Bgt=3D3B  VAR buf: ARRAY [0..0] OF =3D<br>&gt=3B &gt=3B&gt=3B CH=
>> AR=3D3D3B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B  BEGIN&l=
>> t=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B    IF fromCh=3D<br>=
>> &gt=3B &gt=3B&gt=3B arCache [c] =3D3D3D NIL THEN&lt=3Bbr&gt=3B&amp=3Bgt=3D3=
>> B &amp=3Bgt=3D3B&amp=3Bgt=3D3B      buf [0] :=3D3D3D c=3D3D3=3D<br>&gt=3B &=
>> gt=3B&gt=3B B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B     =
>> fromCharCache[c] :=3D3D3D Text8.New (buf)=3D3D3B&lt=3B=3D<br>&gt=3B &gt=3B=
>> &gt=3B br&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B    END=3D3D3B&lt=
>> =3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B    RETURN fromCha=3D=
>> <br>&gt=3B &gt=3B&gt=3B rCache [c]&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D=
>> 3B&amp=3Bgt=3D3B  END FromChar=3D3D3B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=
>> =3D3B&amp=3Bgt=3D3B=3D<br>&gt=3B &gt=3B&gt=3B &lt=3Bbr&gt=3B&amp=3Bgt=3D3B =
>> &amp=3Bgt=3D3B&amp=3Bgt=3D3B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=
>> =3Bgt=3D3BIt should be:&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D<br>&gt=3B =
>> &gt=3B&gt=3B =3D3B&amp=3Bgt=3D3B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B=
>> &amp=3Bgt=3D3B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3BPROC=
>> EDURE FromChar (=3D<br>&gt=3B &gt=3B&gt=3B c: CHAR): T =3D3D3D&lt=3Bbr&gt=
>> =3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B=3D3D0A=3D3D&lt=3Bbr&gt=3B&am=
>> p=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B  VA=3D<br>&gt=3B &gt=3B&gt=3B R bu=
>> f: ARRAY [0..0] OF CHAR=3D3D3B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&a=
>> mp=3Bgt=3D3B=3D3D0A=3D3D&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3B=3D<br>&gt=3B &=
>> gt=3B&gt=3B gt=3D3B&amp=3Bgt=3D3B  BEGIN&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=
>> =3Bgt=3D3B&amp=3Bgt=3D3B=3D3D0A=3D3D&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=
>> =3D3B&amp=3Bgt=3D3B   =3D<br>&gt=3B &gt=3B&gt=3B IF fromCharCache [c] =3D3D=
>> 3D NIL THEN&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B=3D3D0A=
>> =3D3D&lt=3Bbr&gt=3B&amp=3Bgt=3D<br>&gt=3B &gt=3B&gt=3B =3D3B &amp=3Bgt=3D3B=
>> &amp=3Bgt=3D3B      buf [0] :=3D3D3D c=3D3D3B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &=
>> amp=3Bgt=3D3B&amp=3Bgt=3D3B=3D3D0A=3D3D&lt=3B=3D<br>&gt=3B &gt=3B&gt=3B br&=
>> gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B      WITH a =3D3D3D Text8.=
>> New (buf) DO&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D<br>&gt=3B &gt=3B&gt=
>> =3B =3D3B&amp=3Bgt=3D3B        MemoryBarrier()=3D3D3B&lt=3Bbr&gt=3B&amp=3Bg=
>> t=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B        fromCha=3D<br>&gt=3B &gt=3B&gt=
>> =3B rCache[c] :=3D3D3D a=3D3D3B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&=
>> amp=3Bgt=3D3B     END=3D3D3B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D<br>&g=
>> t=3B &gt=3B&gt=3B =3D3B&amp=3Bgt=3D3B=3D3D0A=3D3D&lt=3Bbr&gt=3B&amp=3Bgt=3D=
>> 3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B    END=3D3D3B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &=
>> amp=3Bgt=3D3B&amp=3Bgt=3D3B=3D<br>&gt=3B &gt=3B&gt=3B =3D3D0A=3D3D&lt=3Bbr&=
>> gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B    RETURN fromCharCache [c=
>> ]&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D<br>&gt=3B &gt=3B&gt=3B =3D3B&amp=
>> =3Bgt=3D3B=3D3D0A=3D3D&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=
>> =3D3B  END FromChar=3D3D3B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D<br>&gt=
>> =3B &gt=3B&gt=3B =3D3B&amp=3Bgt=3D3B=3D3D0A=3D3D&lt=3Bbr&gt=3B&amp=3Bgt=3D3=
>> B &amp=3Bgt=3D3B&amp=3Bgt=3D3B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&a=
>> mp=3Bgt=3D3B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3B=3D<br>&gt=3B &gt=3B&gt=3B =
>> gt=3D3B&amp=3Bgt=3D3Bto ensure that all of Text8.New() finishes before the =
>> assignment=3D<br>&gt=3B &gt=3B&gt=3B to fromCha=3D3D&lt=3Bbr&gt=3B&amp=3Bgt=
>> =3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3BrCache[c] is made.&lt=3Bbr&gt=3B&amp=3Bgt=
>> =3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D<br>&gt=3B &gt=3B&gt=3B =3D3B&lt=3Bbr&gt=3B=
>> &amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &am=
>> p=3Bgt=3D3B&amp=3Bgt=3D3BCan the compiler somehow c=3D<br>&gt=3B &gt=3B&gt=
>> =3B atch these?&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3BI f=
>> ear they are a small epidemic.&lt=3Bbr&gt=3B&amp=3Bgt=3D<br>&gt=3B &gt=3B&g=
>> t=3B =3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3BFor a long time people didn't realiz=
>> e where all the compile=3D<br>&gt=3B &gt=3B&gt=3B r and processor =3D3D&lt=
>> =3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3Bcould reorder.&lt=3Bb=
>> r&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bg=3D<br>&gt=3B &gt=3B&gt=3B t=3D=
>> 3B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B&lt=3Bbr&gt=3B&a=
>> mp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3BDo we have the right cons=3D<br>&g=
>> t=3B &gt=3B&gt=3B tructs by now to fix them?&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &a=
>> mp=3Bgt=3D3B&amp=3Bgt=3D3BI think we do.&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=
>> =3B=3D<br>&gt=3B &gt=3B&gt=3B gt=3D3B&amp=3Bgt=3D3B&lt=3Bbr&gt=3B&amp=3Bgt=
>> =3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D=
>> 3B&amp=3Bgt=3D3B - Jay&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3B=3D<br>&gt=3B &gt=
>> =3B&gt=3B gt=3D3B&amp=3Bgt=3D3B                         =3D3D&lt=3Bbr&gt=3B=
>> &amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &am=
>> p=3Bgt=3D3B&amp=3Bgt=3D3B--_=3D<br>&gt=3B &gt=3B&gt=3B 5f23896e-68ee-44da-8=
>> 2dd-311cd8c58979_&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3BC=
>> ontent-Type: t=3D<br>&gt=3B &gt=3B&gt=3B ext/html=3D3B charset=3D3D"iso-885=
>> 9-1"&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3BContent-Transf=
>> er-E=3D<br>&gt=3B &gt=3B&gt=3B ncoding: quoted-printable&lt=3Bbr&gt=3B&amp=
>> =3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3B=
>> gt=3D3B&amp=3Bgt=3D3B&amp=3Blt=3D<br>&gt=3B &gt=3B&gt=3B =3D3Bhtml&amp=3Bgt=
>> =3D3B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B&amp=3Blt=3D3=
>> Bhead&amp=3Bgt=3D3B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3=
>> B=3D<br>&gt=3B &gt=3B&gt=3B &amp=3Blt=3D3Bstyle&amp=3Bgt=3D3B&amp=3Blt=3D3B=
>> !--&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B.hmmessage P&lt=
>> =3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D<br>&gt=3B &gt=3B&gt=3B =3D3B&amp=3Bg=
>> t=3D3B{&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3Bmargin:0px=
>> =3D3D3B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3Bpadd=3D<br>=
>> &gt=3B &gt=3B&gt=3B ing:0px&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=
>> =3Bgt=3D3B}&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3Bbody.hm=
>> message&lt=3Bbr&gt=3B&amp=3Bgt=3D<br>&gt=3B &gt=3B&gt=3B =3D3B &amp=3Bgt=3D=
>> 3B&amp=3Bgt=3D3B{&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3Bf=
>> ont-size: 12pt=3D3D3B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D<br>&gt=3B &g=
>> t=3B&gt=3B =3D3B&amp=3Bgt=3D3Bfont-family:Calibri&lt=3Bbr&gt=3B&amp=3Bgt=3D=
>> 3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B}&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B=
>> &amp=3Bgt=3D3B=3D<br>&gt=3B &gt=3B&gt=3B --&amp=3Bgt=3D3B&amp=3Blt=3D3B/sty=
>> le&amp=3Bgt=3D3B&amp=3Blt=3D3B/head&amp=3Bgt=3D3B&lt=3Bbr&gt=3B&amp=3Bgt=3D=
>> 3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B&amp=3Blt=3D3Bbod=3D<br>&gt=3B &gt=3B&gt=3B =
>> y class=3D3D3D'hmmessage'&amp=3Bgt=3D3B&amp=3Blt=3D3Bdiv dir=3D3D3D'ltr'&am=
>> p=3Bgt=3D3BWe have race cond=3D<br>&gt=3B &gt=3B&gt=3B itions=3D3D2C like =
>> =3D3D&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3Bthis=3D3D2C m=
>> 3core/src/Text.m3:&amp=3Blt=3D<br>&gt=3B &gt=3B&gt=3B =3D3Bbr&amp=3Bgt=3D3B=
>> &amp=3Blt=3D3Bbr&amp=3Bgt=3D3B&amp=3Blt=3D3Bbr&amp=3Bgt=3D3BVAR fromCharCac=
>> he :=3D3D3D ARRAY CHAR =3D<br>&gt=3B &gt=3B&gt=3B OF=3D3D&lt=3Bbr&gt=3B&amp=
>> =3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B T {NIL=3D3D2C ..}=3D3D3B (* 1-char =
>> texts *)&amp=3Blt=3D3Bb=3D<br>&gt=3B &gt=3B&gt=3B r&amp=3Bgt=3D3B&amp=3Blt=
>> =3D3Bbr&amp=3Bgt=3D3B&amp=3Blt=3D3Bbr&amp=3Bgt=3D3BPROCEDURE FromChar (c: C=
>> HAR=3D3D&lt=3Bbr&gt=3B&amp=3Bgt=3D3B=3D<br>&gt=3B &gt=3B&gt=3B &amp=3Bgt=3D=
>> 3B&amp=3Bgt=3D3B): T =3D3D3D&amp=3Blt=3D3Bbr&amp=3Bgt=3D3B&amp=3Bamp=3D3Bnb=
>> sp=3D3D3B VAR buf: ARRAY [0..0]=3D<br>&gt=3B &gt=3B&gt=3B OF CHAR=3D3D3B&am=
>> p=3Blt=3D3Bbr&amp=3Bgt=3D3B&amp=3Bamp=3D3Bnbsp=3D3D3B BEGIN&amp=3Blt=3D3Bbr=
>> &amp=3Bgt=3D3B=3D3D&lt=3Bbr&gt=3B&amp=3Bgt=3D<br>&gt=3B &gt=3B&gt=3B =3D3B =
>> &amp=3Bgt=3D3B&amp=3Bgt=3D3B&amp=3Bamp=3D3Bnbsp=3D3D3B&amp=3Bamp=3D3Bnbsp=
>> =3D3D3B&amp=3Bamp=3D3Bnbsp=3D3D3B IF fromCha=3D<br>&gt=3B &gt=3B&gt=3B rCac=
>> he [c] =3D3D3D NIL THEN&amp=3Blt=3D3Bbr&amp=3Bgt=3D3B&amp=3Bamp=3D3Bnbsp=3D=
>> 3D3B&amp=3Bamp=3D3Bnbsp=3D3D&lt=3Bbr&gt=3B&amp=3Bg=3D<br>&gt=3B &gt=3B&gt=
>> =3B t=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B=3D3D3B&amp=3Bamp=3D3Bnbsp=3D3D3B&am=
>> p=3Bamp=3D3Bnbsp=3D3D3B&amp=3Bamp=3D3Bnbsp=3D3D3B buf =3D<br>&gt=3B &gt=3B&=
>> gt=3B [0] :=3D3D3D c=3D3D3B&amp=3Blt=3D3Bbr&amp=3Bgt=3D3B&amp=3Bamp=3D3Bnbs=
>> p=3D3D3B&amp=3Bamp=3D3Bnbsp=3D3D3B&amp=3Bamp=3D3Bnbsp=3D<br>&gt=3B &gt=3B&g=
>> t=3B =3D3D3B&amp=3Bamp=3D3Bn=3D3D&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3=
>> B&amp=3Bgt=3D3Bbsp=3D3D3B&amp=3Bamp=3D3Bnbsp=3D3D3B fromCharCac=3D<br>&gt=
>> =3B &gt=3B&gt=3B he[c] :=3D3D3D Text8.New (buf)=3D3D3B&amp=3Blt=3D3Bbr&amp=
>> =3Bgt=3D3B&amp=3Bamp=3D3Bnbsp=3D3D3B&amp=3Bamp=3D3Bnbsp=3D<br>&gt=3B &gt=3B=
>> &gt=3B =3D3D3B=3D3D&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3=
>> B&amp=3Bamp=3D3Bnbsp=3D3D3B END=3D3D3B&amp=3Blt=3D3Bbr&amp=3Bgt=3D3B&amp=3B=
>> amp=3D<br>&gt=3B &gt=3B&gt=3B =3D3Bnbsp=3D3D3B&amp=3Bamp=3D3Bnbsp=3D3D3B&am=
>> p=3Bamp=3D3Bnbsp=3D3D3B RETURN fromCharCache [c]&amp=3Blt=3D3B=3D<br>&gt=3B=
>> &gt=3B&gt=3B br&amp=3Bgt=3D3B&amp=3Bamp=3D3Bnb=3D3D&lt=3Bbr&gt=3B&amp=3Bgt=
>> =3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3Bsp=3D3D3B END FromChar=3D3D3B&amp=3Blt=3D=
>> 3Bb=3D<br>&gt=3B &gt=3B&gt=3B r&amp=3Bgt=3D3B&amp=3Blt=3D3Bbr&amp=3Bgt=3D3B=
>> &amp=3Blt=3D3Bbr&amp=3Bgt=3D3BIt should be:&amp=3Blt=3D3Bbr&amp=3Bgt=3D3B&a=
>> mp=3Blt=3D3Bbr&amp=3Bgt=3D<br>&gt=3B &gt=3B&gt=3B =3D3B&amp=3Blt=3D3Bbr&amp=
>> =3Bgt=3D3BPROCEDURE FromCha=3D3D&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B=
>> &amp=3Bgt=3D3Br (c: CHAR): T =3D<br>&gt=3B &gt=3B&gt=3B =3D3D3D&amp=3Blt=3D=
>> 3Bbr&amp=3Bgt=3D3B=3D3D0A=3D3D&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&a=
>> mp=3Bgt=3D3B&amp=3Bamp=3D3Bnbsp=3D3D3B VAR buf:=3D<br>&gt=3B &gt=3B&gt=3B A=
>> RRAY [0..0] OF CHAR=3D3D3B&amp=3Blt=3D3Bbr&amp=3Bgt=3D3B=3D3D0A=3D3D&lt=3Bb=
>> r&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B&amp=3Bamp=3D<br>&gt=3B &=
>> gt=3B&gt=3B =3D3Bnbsp=3D3D3B BEGIN&amp=3Blt=3D3Bbr&amp=3Bgt=3D3B=3D3D0A=3D3=
>> D&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B&amp=3Bamp=3D3Bnb=
>> sp=3D<br>&gt=3B &gt=3B&gt=3B =3D3D3B&amp=3Bamp=3D3Bnbsp=3D3D3B&amp=3Bamp=3D=
>> 3Bnbsp=3D3D3B IF fromCharCache [c] =3D3D3D NIL THEN&amp=3Bl=3D<br>&gt=3B &g=
>> t=3B&gt=3B t=3D3Bbr&amp=3Bgt=3D3B=3D3D0A=3D3D&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &=
>> amp=3Bgt=3D3B&amp=3Bgt=3D3B&amp=3Bamp=3D3Bnbsp=3D3D3B&amp=3Bamp=3D3Bnbsp=3D=
>> 3D3B=3D<br>&gt=3B &gt=3B&gt=3B &amp=3Bamp=3D3Bnbsp=3D3D3B&amp=3Bamp=3D3Bnbs=
>> p=3D3D3B&amp=3Bamp=3D3Bnbsp=3D3D3B buf [0] :=3D3D3D c=3D3D3B&amp=3Blt=3D<br=
>>> &gt=3B &gt=3B&gt=3B =3D3Bbr&amp=3Bgt=3D3B=3D3D0A=3D3D&lt=3Bbr&gt=3B&amp=3B=
>> gt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B&amp=3Bamp=3D3Bnbsp=3D3D3B&amp=3Bamp=3D=
>> 3Bnbsp=3D3D3B&amp=3B=3D<br>&gt=3B &gt=3B&gt=3B amp=3D3Bnbsp=3D3D3B&amp=3Bam=
>> p=3D3Bnbsp=3D3D3B&amp=3Bamp=3D3Bnbsp=3D3D3B WITH a =3D3D3D Text8.New (buf=
>> =3D<br>&gt=3B &gt=3B&gt=3B ) DO&amp=3Blt=3D3Bbr&amp=3Bgt=3D3B&amp=3Bamp=3D3=
>> B=3D3D&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3Bnbsp=3D3D3B&=
>> amp=3Bamp=3D3Bnbsp=3D3D3=3D<br>&gt=3B &gt=3B&gt=3B B&amp=3Bamp=3D3Bnbsp=3D3=
>> D3B&amp=3Bamp=3D3Bnbsp=3D3D3B&amp=3Bamp=3D3Bnbsp=3D3D3B&amp=3Bamp=3D3Bnbsp=
>> =3D3D3B&amp=3Bamp=3D3Bnbs=3D<br>&gt=3B &gt=3B&gt=3B p=3D3D3B MemoryBarrier(=
>> )=3D3D3B&amp=3Blt=3D3B=3D3D&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=
>> =3Bgt=3D3Bbr&amp=3Bgt=3D3B&amp=3Bamp=3D3Bn=3D<br>&gt=3B &gt=3B&gt=3B bsp=3D=
>> 3D3B&amp=3Bamp=3D3Bnbsp=3D3D3B&amp=3Bamp=3D3Bnbsp=3D3D3B&amp=3Bamp=3D3Bnbsp=
>> =3D3D3B&amp=3Bamp=3D3Bnbsp=3D3D3B&amp=3Bam=3D<br>&gt=3B &gt=3B&gt=3B p=3D3B=
>> nbsp=3D3D3B&amp=3Bamp=3D3Bnbsp=3D3D3B fromCharCache[c=3D3D&lt=3Bbr&gt=3B&am=
>> p=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B] :=3D<br>&gt=3B &gt=3B&gt=3B =3D3D=
>> 3D a=3D3D3B&amp=3Blt=3D3Bbr&amp=3Bgt=3D3B&amp=3Bamp=3D3Bnbsp=3D3D3B&amp=3Ba=
>> mp=3D3Bnbsp=3D3D3B&amp=3Bamp=3D3Bnbsp=3D3D3B&amp=3B=3D<br>&gt=3B &gt=3B&gt=
>> =3B amp=3D3Bnbsp=3D3D3B END=3D3D3B&amp=3Blt=3D3Bbr&amp=3Bgt=3D3B=3D3D0A=3D3=
>> D&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B&amp=3Bamp=3D<br>=
>> &gt=3B &gt=3B&gt=3B =3D3Bnbsp=3D3D3B&amp=3Bamp=3D3Bnbsp=3D3D3B&amp=3Bamp=3D=
>> 3Bnbsp=3D3D3B END=3D3D3B&amp=3Blt=3D3Bbr&amp=3Bgt=3D3B=3D3D0A=3D3D=3D<br>&g=
>> t=3B &gt=3B&gt=3B &lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B=
>> &amp=3Bamp=3D3Bnbsp=3D3D3B&amp=3Bamp=3D3Bnbsp=3D3D3B&amp=3Bamp=3D3Bnbsp=3D3=
>> D3B RET=3D<br>&gt=3B &gt=3B&gt=3B URN fromCharCache [c]&amp=3Blt=3D3Bbr&amp=
>> =3Bgt=3D3B=3D3D0A=3D3D&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=
>> =3D3B&amp=3Bamp=3D3Bnb=3D<br>&gt=3B &gt=3B&gt=3B sp=3D3D3B END FromChar=3D3=
>> D3B&amp=3Blt=3D3Bbr&amp=3Bgt=3D3B=3D3D0A=3D3D&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &=
>> amp=3Bgt=3D3B&amp=3Bgt=3D3B&amp=3Blt=3D<br>&gt=3B &gt=3B&gt=3B =3D3Bbr&amp=
>> =3Bgt=3D3B&amp=3Blt=3D3Bbr&amp=3Bgt=3D3Bto ensure that all of Text8.New() f=
>> inishes before =3D<br>&gt=3B &gt=3B&gt=3B the assignment to=3D3D&lt=3Bbr&gt=
>> =3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B fromCharCache[c] is made.&am=
>> p=3Blt=3D3B=3D<br>&gt=3B &gt=3B&gt=3B br&amp=3Bgt=3D3B&amp=3Blt=3D3Bbr&amp=
>> =3Bgt=3D3B&amp=3Blt=3D3Bbr&amp=3Bgt=3D3BCan the compiler somehow catch thes=
>> e?=3D<br>&gt=3B &gt=3B&gt=3B =3D3D&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D=
>> 3B&amp=3Bgt=3D3B&amp=3Blt=3D3Bbr&amp=3Bgt=3D3BI fear they are a small epide=
>> mic.&amp=3Bl=3D<br>&gt=3B &gt=3B&gt=3B t=3D3Bbr&amp=3Bgt=3D3BFor a long tim=
>> e people didn't real=3D3D&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3B=
>> gt=3D3Bize=3D<br>&gt=3B &gt=3B&gt=3B where all the compiler and processor c=
>> ould reorder.&amp=3Blt=3D3Bbr&amp=3Bgt=3D3B&amp=3Blt=3D3Bbr&amp=3B=3D<br>&g=
>> t=3B &gt=3B&gt=3B gt=3D3B&amp=3Blt=3D3Bbr&amp=3Bgt=3D3BDo we ha=3D3D&lt=3Bb=
>> r&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3Bve the right construct=3D=
>> <br>&gt=3B &gt=3B&gt=3B s by now to fix them?&amp=3Blt=3D3Bbr&amp=3Bgt=3D3B=
>> I think we do.&amp=3Blt=3D3Bbr&amp=3Bgt=3D3B&amp=3Blt=3D3Bbr&amp=3Bgt=3D<br=
>>> &gt=3B &gt=3B&gt=3B =3D3B&amp=3Blt=3D3Bbr&amp=3Bgt=3D3B -=3D3D&lt=3Bbr&gt=
>> =3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B Jay&amp=3Blt=3D3Bbr&amp=3Bgt=
>> =3D3B                         =3D<br>&gt=3B &gt=3B&gt=3B &amp=3Blt=3D3B/div=
>> &amp=3Bgt=3D3B&amp=3Blt=3D3B/body&amp=3Bgt=3D3B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B=
>> &amp=3Bgt=3D3B&amp=3Bgt=3D3B&amp=3Blt=3D3B/html&amp=3Bgt=3D3B=3D<br>&gt=3B=
>> &gt=3B&gt=3B =3D3D&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3=
>> B&lt=3Bbr&gt=3B&amp=3Bgt=3D3B &amp=3Bgt=3D3B&amp=3Bgt=3D3B--_5f23896e-68ee-=
>> 44da-82dd=3D<br>&gt=3B &gt=3B&gt=3B -311cd8c58979_--&lt=3Bbr&gt=3B&lt=3B/di=
>> v&gt=3B                         &lt=3B/div&gt=3B&lt=3B/body&gt=3B<br>&gt=3B=
>> &gt=3B&gt=3B &lt=3B/html&gt=3B=3D<br>&gt=3B &gt=3B&gt=3B <br>&gt=3B &gt=3B=
>> &gt=3B --_86f22d85-5540-4565-bf73-232aaafdc94b_--<br></div> 		 	   		  </di=
>> v></body>
>> </html>=
>> 
>> --_5c33c9ca-3a7d-4c39-ab66-ab9c151d1539_--




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