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Conference azur::mcc

Title:	DECmcc user notes file. Does not replace IPMT.
Notice:	Use IPMT for problems. Newsletter location in note 6187
Moderator:	TAEC::BEROUD

Created:	Mon Aug 21 1989
Last Modified:	Wed Jun 04 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	6497
Total number of notes:	27359

2355.0. "Condition variable routines?" by QUIVER::DESMOND () Mon Feb 17 1992 19:40

    Are there any MCC jacket routines for condition variables?  If not, do
    I just use the CMA condition variable routines?
    
    							John

T.R	Title	User	Personal Name	Date	Lines
2355.1	There are routines .. but they didn't get documented for Field Test	MOLAR::ROBERTS	Keith Roberts - DECmcc Toolkit Team	`Tue Feb 18 1992 08:50`	9
	John, Yes, there are DECmcc Condition Variable routine wrappers ... but they didn't get documented for Field Test. There is an ULTRIX ECO which will add these routines to the SRM. I will post the draft edition of these routines in the next reply -- Hopefully they are correct 8) /keith
2355.2	Draft copy of DECmcc SRM Condition Variable routines	MOLAR::ROBERTS	Keith Roberts - DECmcc Toolkit Team	`Tue Feb 18 1992 08:54`	668
	mcc_condition_broadcast __________________________________________________________________ mcc_condition_broadcast-Broadcast on a condition variable Broadcast on a condition variable, unblocking all threads currently waiting on the condition variable. __________________________________________________________________ FORMAT mcc_condition_broadcast condition __________________________________________________________________ RETURNS MCC Usage: cond_value data type: MCC_T_CVR access: write only mechanism: by value Condition values that this routine returns are listed under CONDITION VALUES RETURNED __________________________________________________________________ ARGUMENTS CONDITION MCC Usage: handle data type: MCC_T_CONDVAR access: read only mechanism: by reference Handle of condition variable to be broadcast condition-22 mcc_condition_broadcast __________________________________________________________________ DESCRIPTION This routine wakes up all threads waiting on the condition variable. This operation must be called when data guarded by the mutex associated with the condition variable has been changed in such a way the it might be possible for more than one thread waiting on the condition to proceed. For example, this would be used to wake up all readers waiting for shared read access to some data. This routine is not alertable. __________________________________________________________________ CONDITION VALUES RETURNED MCC_S_NORMAL Normal successful completion MCC_S_EXISTENCE_ Object does not exist ERROR MCC_S_INVOBJTYPE Invalid type of referenced object MCC_S_REQARG Required argument is missing MCC_S_USE_ERROR Incorrect use of handle MCC_S_ Wrong number of arguments WRONGNUMARGS condition-23 mcc_condition_create __________________________________________________________________ mcc_condition_create-Create a condition variable This routine creates and initializes a condition variable object and returns its handle. __________________________________________________________________ FORMAT mcc_condition_create condition __________________________________________________________________ RETURNS MCC Usage: cond_value data type: MCC_T_CVR access: write only mechanism: by value Condition values that this routine returns are listed under CONDITION VALUES RETURNED __________________________________________________________________ ARGUMENTS CONDITION MCC Usage: Handle data type: MCC_T_CONDVAR access: write only mechanism: by reference Variable that receives the handle for the new condition-variable. condition-24 mcc_condition_create __________________________________________________________________ DESCRIPTION This procedure creates and initializes a condition variable object and returns its handle which may be shared by threads to access the object. Condition variables created by this procedure are not owned by any particular thread and any associated storage is not automatically recleaimed if the creating thread terminates. This routine is not alertable. __________________________________________________________________ CONDITION VALUES RETURNED MCC_S_NORMAL Normal successful completion MCC_S_EXISTENCE_ Object does not exist ERROR MCC_S_INSVIRMEM Insufficient virtual memory MCC_S_REQARG Required argument is missing MCC_S_USE_ERROR Incorrect use of handle MCC_S_ Wrong number of arguments WRONGNUMARGS condition-25 mcc_condition_delete __________________________________________________________________ mcc_condition_delete-Delete a condition variable This routine deletes a condition variable __________________________________________________________________ FORMAT mcc_condition_delete condition __________________________________________________________________ RETURNS MCC Usage: cond_value data type: MCC_T_CVR access: write only mechanism: by value Condition values that this routine returns are listed under CONDITION VALUES RETURNED __________________________________________________________________ ARGUMENTS CONDITION MCC Usage: handle data type: MCC_T_CONDVAR access: modify mechanism: by reference Handle for the condition variable that will no longer be referenced. condition-26 mcc_condition_delete __________________________________________________________________ DESCRIPTION This operation should be called when a condition variable will no longer be referenced by any threads. The effect of this operation is to give permission to reclaim storage for the condition variable. The condition variable is deleted and the CONDITION parameter is set to the value MCC_K_ NULL. Calling this operation with a CONDITION parameter of MCC_K_NULL is legal and has no effect. If the condition variable currently has waiting threads, then the operation will fail and an error condition code (MCC_S_IN_USE_ERROR) will be returned. If the mutex does not exist, then the operation will fail and an error condition code (MCC_S_ EXISTENCE) will be returned. This routine is not alertable. __________________________________________________________________ CONDITION VALUES RETURNED MCC_S_NORMAL Normal success completion MCC_S_EXISTENCE_ The object does not exist ERROR MCC_S_IN_USE_ The object is currently in use ERROR MCC_S_INVOBJTYPE Invalid type of referenced object MCC_S_REQARG Required argument is missing MCC_S_USE_ERROR Incorrect use of handle MCC_S_ Wrong number of arguments WRONGNUMARGS condition-27 mcc_condition_signal __________________________________________________________________ mcc_condition_signal-Signal a condition variable Signal a condition variable, unblocking one thread waiting on the condition variable. __________________________________________________________________ FORMAT mcc_condition_signal condition __________________________________________________________________ RETURNS MCC Usage: cond_value data type: MCC_T_CVR access: write only mechanism: by value Condition values that this routine returns are listed under CONDITION VALUES RETURNED __________________________________________________________________ ARGUMENTS CONDITION MCC Usage: handle data type: MCC_T_CONDVAR access: read only mechanism: by reference Handle of condition variable to be signaled condition-28 mcc_condition_signal __________________________________________________________________ DESCRIPTION This routine wakes up one thread currently waiting on the condition variable. This operation must be called when data guarded by the mutex associated with the condition variable has been changed in such a way the it might be possible for one thread waiting on the condition to proceed. For example, this would be used to wake up a thread waiting for exclusive access to some data. This operation can be called with the mutex either locked or unlocked. This routine is not alertable. __________________________________________________________________ CONDITION VALUES RETURNED MCC_S_NORMAL Normal successful completion MCC_S_EXISTENCE_ Object does not exist ERROR MCC_S_INVOBJTYPE Invalid type of referenced object MCC_S_REQARG Required argument is missing MCC_S_USE_ERROR Incorrect use of handle MCC_S_ Wrong number of arguments WRONGNUMARGS condition-29 mcc_condition_wait __________________________________________________________________ mcc_condition_wait-Wait for condition variable A thread can wait for a condition variable to be signaled or broadcast by calling this procedure. __________________________________________________________________ FORMAT mcc_condition_wait condition, mutex __________________________________________________________________ RETURNS MCC Usage: cond_value data type: MCC_T_CVR access: write only mechanism: by value Condition values that this routine returns are listed under CONDITION VALUES RETURNED __________________________________________________________________ ARGUMENTS CONDITION MCC Usage: handle data type: MCC_T_CONDVAR access: read only mechanism: by reference The condition variable to be waited on. condition-30 mcc_condition_wait mutex MCC Usage: handle data type: MCC_T_MUTEX access: read only mechanism: by reference Handle of mutex associated with the condition variable. __________________________________________________________________ DESCRIPTION This operation must be called with the mutex locked. This operation automatically releases the mutex and causes the thread to wait on the condition. If the wait is satisfied as a result of some thread calling MCC_CONDITION_BROADCAST or MCC_CONDITION_SIGNAL, then the mutex is reacquired and the procedure returns. This operation might (with low probability) return spuriously without the condition variable being signalled or broadcast. It is recommended that the client retest the predicate condition after returning from this operation. If the operation fails to unlock the mutex, then the operation will fail and the error condition will be returned. If the routine is alerted, then the mutex will be reacquired before returning. This routine is alertable. condition-31 mcc_condition_wait __________________________________________________________________ CONDITION VALUES RETURNED MCC_S_NORMAL Normal successful completion MCC_S_EXISTENCE_ Object does not exist ERROR MCC_S_IN_USE_ Object is currently in use ERROR MCC_S_INVOBJTYPE Invalid type of referenced object MCC_S_REQARG Required argument is missing MCC_S_USE_ERROR Incorrect use of handle MCC_S_ Wrong number of arguments WRONGNUMARGS
2355.3	MCC wrappers are meant to be transitionary	TOOK::BURGESS		`Tue Feb 18 1992 13:42`	16
	The mcc condition variable and mutex routines are layered on DECthreads. You may choose to use the CMA or POSIX API to the synchronization primitives or other threading services. When the POSIX API evolves from a draft to a standard, then this API will be the prefered interface to multi-threading services. In the mean time you have 3 sub-optimum API choices: o POSIX draft 1003.4a which might change o CMA which won't change but might not be found on as many platforms as the POSIX API o MCC wrappers which currently use the CMA interface. \Pete