Re: locks

["Steve Richter" <srichter@xxxxxxxxxxxxx>]

/* Using CMPSW to implement an InterlockedIncrement( ) function. */
/* this is a lot faster than LOCKSL, Inc value, UNLOCKSL. */

DCL SPCPTR  pGlobalCount  AUTO ;
DCL DD  nGlobalCount  BIN(2) BAS(pGlobalCount) ;
DCL DD  nWasCount, nIncCount  BIN(2) AUTO ;

BgnInc:

    CPYNV     nWasCount, nGlobalCount ;
    ADDN        nIncCount, nWasCount, 1 ;

/* If Was and Global are equal ( no other thread has gotten to Global ), */
/* set Global = Inc. Otherwise, set Was = Inc. */
    CMPSW    nWasCount, nGlobalCount, nIncCount ;

/* ( should not CMPSW be called CMPCHG ( compare and chg ) ?  */

/* Was and Global were not equal at CMPSW time. */
/* Someone else got to Global since "CPYNV Was, Global". */
/* Branch back and try again. */
    CMPNV(B) nWasCount, nIncCount / EQ(BgnInc) ;
 
EndInc:

/* return with nWasCount and nIncCount.  */
/* the machine guarantees that this code set Global = Inc. */


Thanks for the answers Larry.

Steve Richter



 


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