Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!rutgers!cbmvax!mks
From: mks@cbmvax.UUCP (Michael Sinz - CATS)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Semaphores
Message-ID: <8792@cbmvax.UUCP>
Date: 1 Dec 89 23:54:48 GMT
References: <1716@mathrt0.math.chalmers.se>
Reply-To: mks@cbmvax.UUCP (Michael Sinz - CATS)
Organization: Commodore Technology, West Chester, PA
Lines: 66

In article <1716@mathrt0.math.chalmers.se> d5adria@dtek.chalmers.se (Martin Adrian) writes:
>I can't get the function AddSemaphore to work.
>
>My program looks like this:
>
>main()
>{
>  struct SignalSemaphore ss;
>
>  /* set name and pri */
>
>  AddSemaphore(&ss);

Note that AddSemaphore is Broken in the 1.2/1.3 ROMs and you must use the
work-around published in AmigaMail and in the AutoDocs and in the
RKM: Includes & AutoDocs...  (Blue cover...)

>
>  ....
>
>  RemSemaphore(&ss);
>}
>
>The guru will show up every time with different nubers.
>
>When i disassembled the exec function AddSemaphore it looked like this(Ks1.3):
>AddSemaphore:  JSR   _LVOInitSemaphore(A6)
>	       LEA   SemaphoreList+LH_Head(A6),A0
>	       BRA   xxxx    ;do Enqueue
>
>When i looked up the functions in programmers guide i found that AddSemaphore
>wants the Semaphorepointer in A1 and InitSemaphore in A0.
>(The lattice proto/exec.h was wrong about this)
>
>InitSemaphore also destroys A0,A1,D0,D1.
>
>As far as i can see there is no way that this function can work.
> 
> BTW this macro works fine.
>#define AddSemaphore(ss) InitSemaphore(ss),\
>		         Enqueue(ExecBase->SemaphoreList,&(ss)->ss_Link)
>                                                                 ^ 
>						   the semaphore node 

Note that you need to do the following:

        InitSemaphore(ss);
        Forbid();
        Enqueue(ExecBase->SemaphoreList,ss);
        Permit();

You MUST Forbid()/Permit()

>Is this a known bug in Exec ?
>
>Martin Adrian.



/----------------------------------------------------------------------\
|      /// Michael Sinz -- CATS/Amiga Software Engineer                |
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