Sistemi operativi - Syscall pthread_cond_init

pthread_cond_init, pthread_cond_destroy - initialise and destroy condition variables

The function pthread_cond_init() initialises the condition variable referenced by cond with attributes referenced by attr. If attr is NULL, the default condition variable attributes are used; the effect is the same as passing the address of a default condition variable attributes object. Upon successful initialisation, the state of the condition variable becomes initialised. Attempting to initialise an already initialised condition variable results in undefined behaviour.

The function pthread_cond_destroy() destroys the given condition variable.

condition variable specified by cond; the object becomes, in effect, uninitialised. An implementation may cause pthread_cond_destroy() to set the object referenced by cond to an invalid value. A destroyed condition variable object can be re-initialised using pthread_cond_init(); the results of otherwise referencing the object after it has been destroyed are undefined.

It is safe to destroy an initialised condition variable upon which no threads are currently blocked. Attempting to destroy a condition variable upon which other threads are currently blocked results in undefined behaviour.

In cases where default condition variable attributes are appropriate, the macro PTHREAD_COND_INITIALIZER can be used to initialise condition variables that are statically allocated. The effect is equivalent to dynamic initialisation by a call to pthread_cond_init() with parameter attr specified as NULL, except that no error checks are performed.

RETURN VALUE

If successful, the pthread_cond_init() and

The pthread_cond_destroy() function returns zero. Otherwise, an error number is returned to indicate the error. The [EBUSY] and [EINVAL] error checks, if implemented, act as if they were performed immediately at the beginning of processing for the function and caused an error return prior to modifying the state of the condition variable specified by cond.

ERRORS:

1. [EBUSY]: The implementation has detected an attempt to destroy the object referenced by cond while it is in use by another thread.
2. [EINVAL]: The value specified by cond does not refer to a valid condition variable.