pthread_cond_init.3t (2010 09)

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pthread_cond_init(3T) pthread_cond_init(3T)

(Pthread Library)

NAME

pthread_cond_init(), pthread_cond_destroy() - initialize or destroy a condition variable

SYNOPSIS

#include <pthread.h>

int pthread_cond_init(

pthread_cond_t *__restrict cond,

const pthread_condattr_t *__restrict attr

);

pthread_cond_t cond = PTHREAD_COND_INITIALIZER;

int pthread_cond_destroy(

pthread_cond_t *cond

);

PARAMETERS

cond Pointer to the condition variable to be initialized or destroyed.

attr Pointer to the attributes object that deﬁnes the characteristics of the condition variable to

be initialized. If the pointer is NULL, default attributes are used.

DESCRIPTION

The pthread_cond_init()

function initializes the condition variable cond with the attributes attr .

If attr is NULL, the default condition variable attributes are used to initialize the attributes object. See

pthread_condattr_init(3T) for a list of the default condition variable attributes. After successful initiali-

zation, the condition variable may be used in condition variable operations. A condition variable should

be initialized only once or the resulting behavior is undeﬁned. The

pthread_once()

function provides

a way to ensure that a condition variable is only initialized once.

The macro

PTHREAD_COND_INITIALIZER

can be used to initialize condition variables that are stati-

cally allocated. These condition variables will be initialized with default attributes. The

pthread_cond_init()

function does not need to be called for statically initialized condition vari-

ables.

If the process-shared attribute in the condition variable attributes object referenced by attr is deﬁned as

PTHREAD_PROCESS_SHARED

, the condition variable must be allocated such that the processes sharing

the condition variable have access to it. This may be done through the memory-mapping functions (see

mmap(2)) or the shared memory functions (see shmget (2)).

pthread_cond_destroy()

destroys the condition variable cond . This function may set cond to an

invalid value. The destroyed condition variable can be reinitialized using the function

pthread_cond_init()

. If the condition variable is used after destruction in any condition variable

call, the resulting behavior is undeﬁned.

A condition variable should be destroyed only when there are no threads currently blocked on it. Des-

troying a condition variable that is currently in use results in undeﬁned behavior.

RETURN VALUE

Upon successful completion,

pthread_cond_init() and pthread_cond_destroy()

return zero.

Otherwise, an error number is returned to indicate the error (the

errno variable is not set).

ERRORS

If any of the following occur, the

pthread_cond_init() function returns the corresponding error

number:

[EAGAIN] The system does not have the available resources (other than memory) to initialize

the condition variable.

[EBUSY] The speciﬁed condition variable is an already initialized condition variable. How-

ever, getting [EBUSY] for reinitializing the condition variable cannot be expected

all the time since the behavior of reinitializing the condition variable is undeﬁned.

[EFAULT] The cond parameter points to an illegal address.

[EINVAL] The value speciﬁed by cond or attr is invalid.

HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

Summary of content (2 pages)

PAGE 1
pthread_cond_init(3T) pthread_cond_init(3T) (Pthread Library) NAME pthread_cond_init(), pthread_cond_destroy() - initialize or destroy a condition variable SYNOPSIS #include int pthread_cond_init( pthread_cond_t *__restrict cond, const pthread_condattr_t *__restrict attr ); pthread_cond_t cond = PTHREAD_COND_INITIALIZER; int pthread_cond_destroy( pthread_cond_t *cond ); PARAMETERS cond attr Pointer to the condition variable to be initialized or destroyed.
PAGE 2
pthread_cond_init(3T) pthread_cond_init(3T) (Pthread Library) [ENOMEM] There is insufficient memory available in which to initialize the condition variable. If any of the following occur, the pthread_cond_destroy() function returns the corresponding error number: [EBUSY] An attempt to destroy cond while it is in use by another thread. [EINVAL] cond is not a valid condition variable. WARNINGS The space for condition variable must be allocated before calling pthread_cond_init().