cond_init(SYNCH)

cond_init -- initialize a condition variable

Synopsis

   cc [options] -Kthread file
   
   #include <synch.h>
   

   int cond_init(cond_t *cond, int type, void *arg);

Description

cond_init initializes the condition variable pointed to by cond to be of type type. Once created, the condition cond can be used any number of times without being re-initialized.

Parameters

cond: pointer to condition variable to be initialized
type: USYNC_THREAD or USYNC_PROCESS
arg: NULL (reserved for future use)

cond parameter

cond points to the condition variable to be initialized.

type parameter

type can be set to one of the following values:

USYNC_THREAD: initialize the condition variable for threads within the current process
USYNC_PROCESS: initialize the condition variable for threads across processes

arg parameter

arg should be set to NULL. It is not currently used, but is reserved for future use.

Static condition variable initialization

In this implementation, a condition variable can be initialized statically if its storage is zero-filled. In this case, the condition variable is of type USYNC_THREAD, and cond_init need not be called.

Return values

cond_init returns zero for success and an error number for failure.

Errors

If the following condition is detected, cond_init returns the corresponding value:

EINVAL: invalid type or NULL cond argument specified

Warnings

cond_init does not examine the cond argument before initializing it. If cond_init is called more than once for the same condition, it will overwrite its state. It is the user's responsibility to ensure that cond_init is only called once for each condition variable.

References

Intro(SYNCH), condition(SYNCH), cond_broadcast(SYNCH), cond_destroy(SYNCH), cond_signal(SYNCH), cond_timedwait(SYNCH), cond_wait(SYNCH)