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Re: About lockfree_mpmc -

Cross-posted to 2 groups.

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I wrote:
> So as you have noticed the processor can then reorder the loads on line 
> [2] with the older
> store on line [1] and this will cause a problem, so i think i have to 
> insert a load between
> line [1] and line [2].


Even if i insert a load beween line [1] and [2] this will not work ,
i have to insert an mfence between line [1] and [2].


What do you think ?


Sincerely,
Amine Moulay Ramdane.






"aminer" <aminer@videotron.ca> wrote in message 
news:juhuo3$q5s$1@dont-email.me...
>
> Hello all,
>
> I think i have discovered a problem with lockfree_mpmc:
>
> You will find the source code of lockfree_mpmc at:
>
> http://pages.videotron.com/aminer/
>
>
> So please follow with me:
>
> If you take a look at the lockfree_mpmc , here is  the source code
> of the push() method:
>
> ---
>
> function TLockfree_MPMC.push(tm : tNodeQueue):boolean;
> var lasttail,newtemp:long;
> i,j:integer;
> begin
>
> if getlength >= fsize
>  then
>      begin
>          result:=false;
>          exit;
>      end;
> result:=true;
>
> newTemp:=LockedIncLong(temp);
>
> [1] lastTail:=newTemp-1;
> [2] setObject(lastTail,tm);
>
> repeat
>
> if CAS(tail,lasttail,newtemp)
>   then
>      begin
>       exit;
>      end;
> sleep(0);
> until false;
>
> end;
>
> ---
>
> As you know in the x86 architecture Loads may be reordered with older 
> stores
> to different locations.
>
> So in line [2] there is a load of tail and lasttail to the registers of 
> the processor
> before calling setobject() and just before on line [1] there is a store to 
> lasttail.
>
> So as you have noticed the processor can then reorder the loads on line 
> [2] with the older
> store on line [1] and this will cause a problem, so i think i have to 
> insert a load between
> line [1] and line [2].
>
>
> What do you think ?
>
>
>
> Sincerely,
> Amine Moulay Ramdane.
>
> 

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Thread

About lockfree_mpmc - "aminer" <aminer@videotron.ca> - 2012-07-22 18:27 -0500
  Re: About lockfree_mpmc - "aminer" <aminer@videotron.ca> - 2012-07-22 18:34 -0500
    Re: About lockfree_mpmc - "aminer" <aminer@videotron.ca> - 2012-07-22 18:51 -0500

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