pthread_mutexattr_setkind_np Subroutine

Purpose

Sets the value of the kind attribute of a mutex attributes object.

Library

Threads Library (libpthreads.a)

Syntax

#include <pthread.h>

int pthread_mutexattr_setkind_np ( attr, kind) pthread_mutexattr_t *attr; int kind;

Description

The pthread_mutexattr_setkind_np subroutine sets the value of the kind attribute of the mutex attributes object attr. This attribute specifies the kind of the mutex created with this attributes object.

Note:

The pthread.h header file must be the first included file of each source file using the threads library. Otherwise, the -D_THREAD_SAFE compilation flag should be used, or the cc_r compiler used. In this case, the flag is automatically set.
The pthread_mutexattr_setkind_np subroutine is not portable.

This subroutine is provided only for compatibility with the DCE threads. It should not be used when writing new applications.

Parameters

Item	Description
attr	Specifies the mutex attributes object.
kind	Specifies the kind to set. It must have one of the following values: MUTEX_FAST_NP Denotes a fast mutex. A fast mutex can be locked only once. If the same thread unlocks twice the same fast mutex, the thread will deadlock. Any thread can unlock a fast mutex. A fast mutex is not compatible with the priority inheritance protocol. MUTEX_RECURSIVE_NP Denotes a recursive mutex. A recursive mutex can be locked more than once by the same thread without causing that thread to deadlock. The thread must then unlock the mutex as many times as it locked it. Only the thread that locked a recursive mutex can unlock it. A recursive mutex must not be used with condition variables. MUTEX_NONRECURSIVE_NP Denotes the default non-recursive POSIX compliant mutex.

Item

Description

attr

Specifies the mutex attributes object.

kind

Specifies the kind to set. It must have one of the following values:

MUTEX_FAST_NP: Denotes a fast mutex. A fast mutex can be locked only once. If the same thread unlocks twice the same fast mutex, the thread will deadlock. Any thread can unlock a fast mutex. A fast mutex is not compatible with the priority inheritance protocol.
MUTEX_RECURSIVE_NP: Denotes a recursive mutex. A recursive mutex can be locked more than once by the same thread without causing that thread to deadlock. The thread must then unlock the mutex as many times as it locked it. Only the thread that locked a recursive mutex can unlock it. A recursive mutex must not be used with condition variables.
MUTEX_NONRECURSIVE_NP: Denotes the default non-recursive POSIX compliant mutex.

Return Values

Upon successful completion, 0 is returned. Otherwise, an error code is returned.

Error Codes

The pthread_mutexattr_setkind_np subroutine is unsuccessful if the following is true:

Item	Description
EINVAL	The attr parameter is not valid.
ENOTSUP	The value of the kind parameter is not supported.