pthread_mutexattr_getpshared or pthread_mutexattr_setpshared Subroutine

Purpose

Sets and gets process-shared attribute.

Library

Threads Library (libpthreads.a)

Syntax

#include <pthread.h>

int pthread_mutexattr_getpshared (attr, pshared) const pthread_mutexattr_t *attr; int *pshared;

int pthread_mutexattr_setpshared (attr, pshared) pthread_mutexattr_t *attr; int pshared;

Description

The pthread_mutexattr_getpshared subroutine obtains the value of the process-shared attribute from the attributes object referenced by attr. The pthread_mutexattr_setpshared subroutine is used to set the process-shared attribute in an initialized attributes object referenced by attr.

The process-shared attribute is set to PTHREAD_PROCESS_SHARED to permit a mutex to be operated upon by any thread that has access to the memory where the mutex is allocated, even if the mutex is allocated in memory that is shared by multiple processes. If the process-shared attribute is PTHREAD_PROCESS_PRIVATE, the mutex will only be operated upon by threads created within the same process as the thread that initialized the mutex; if threads of differing processes attempt to operate on such a mutex, the behavior is undefined. The default value of the attribute is PTHREAD_PROCESS_PRIVATE.

Parameters

Item	Description
attr	Specifies the mutex attributes object.
pshared	Points to where the pshared attribute value will be stored.

Return Values

Upon successful completion, the pthread_mutexattr_setpshared subroutine returns zero. Otherwise, an error number is returned to indicate the error.

Upon successful completion, the pthread_mutexattr_getpshared subroutine returns zero and stores the value of the process-shared attribute of attr into the object referenced by the pshared parameter. Otherwise, an error number is returned to indicate the error.

Error Codes

The pthread_mutexattr_getpshared and pthread_mutexattr_setpshared subroutines will fail if:

Item	Description
EINVAL	The value specified by attr is invalid.

The pthread_mutexattr_setpshared function will fail if:

Item	Description
EINVAL	The new value specified for the attribute is outside the range of legal values for that attribute.

These subroutines will not return an error code of EINTR.