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    pthread_mutexattr_init(3T) manual page Table of Contents

Name

pthread_mutexattr_init, pthread_mutexattr_destroy, pthread_mutexattr_setpshared, pthread_mutexattr_getpshared, pthread_mutexattr_setprotocol, pthread_mutexattr_getprotocol, pthread_mutexattr_setprioceiling, pthread_mutexattr_getprioceiling - mutex initialization attributes

Synopsis

#include <pthread.h>

int pthread_mutexattr_init(pthread_mutexattr_t *attr);
int pthread_mutexattr_destroy(pthread_mutexattr_t *attr);
int pthread_mutexattr_setpshared(pthread_mutexattr_t *attr, int process-shared);
int pthread_mutexattr_getpshared(const pthread_mutexattr_t *attr, int *process-shared);

MT-Level

MT-Safe

Description

Initialize

pthread_mutexattr_init() initializes a mutex attributes object, attr, with the default value for its attribute, which is PTHREAD_PROCESS_PRIVATE . If the process-shared attribute is PTHREAD_PROCESS_PRIVATE , only threads created within the same process as the thread that initialized the mutex can access the mutex. If threads of differing processes attempt to access the mutex, the behavior is unpredictable.

Attempts to initialize an already initialized mutex variable attributes object will leave the storage allocated by the previous initialization unallocated.

Once a mutex attributes object is used to initialize one or more mutexes, any function that affects the attributes object (including destruction) will not affect any previously initialized mutexes.

Destroy

pthread_mutexattr_destroy() destroys a mutex attributes object; the object will then become uninitialized. A destroyed mutex attributes object can be reinitialized using pthread_mutexattr_init(). The results of referencing the object after it has been destroyed are undefined.

Set/Get Scope

pthread_mutexattr_setpshared() and pthread_mutexattr_getpshared() sets the process-shared attribute in an initialized attributes object pointed to by attr, and gets the value of the process-shared attribute from the attributes object pointed to by attr, respectively.

At present, only the attribute process-shared is defined.

Unsupported Interfaces

Currently, the following interfaces, which are optional under POSIX, are not supported: 


int pthread_mutexattr_setprotocol (pthread_mutexattr_t *attr, int protocol);

Return Values

Upon successful completion, pthread_mutexattr_init(), pthread_mutexattr_destroy(), pthread_mutexattr_setprotocol(), pthread_mutexattr_getprotocol(), pthread_mutexattr_setprioceiling(), pthread_mutexattr_getprioceiling() , and pthread_mutexattr_setpshared() return 0; otherwise, an error number is returned.

Upon successful completion, pthread_mutexattr_getpshared() returns 0 and stores the value of the process-shared attribute of attr in the object pointed to by the process-shared parameter; otherwise, an error number is returned.

Errors

The function pthread_mutexattr_init() returns an error number if the following condition is detected:
ENOMEM
Insufficient memory exists to initialize the mutex attributes object.

The functions pthread_mutexattr_destroy(), pthread_mutexattr_getpshared(), and pthread_mutexattr_setpshared() return an error number if the following condition is detected:

EINVAL
The value specified by attr is invalid.

The function pthread_mutexattr_setpshared() returns an error number if the following condition is detected:

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

Currently, the functions pthread_mutexattr_setprotocol(), pthread_mutexattr_getprotocol(), pthread_mutexattr_setprioceiling(), and pthread_mutexattr_getprioceiling() always return the following error code:

ENOSYS
These optional interfaces are not supported.

See Also

pthread_cond_init(3T) , pthread_create(3T) , pthread_mutex_init(3T)

Notes

The functions pthread_mutexattr_setprotocol(), pthread_mutexattr_getprotocol(), pthread_mutexattr_setprioceiling(), and pthread_mutexattr_getprioceiling() return ENOSYS in the current implementation, i.e., this function is not currently implemented.

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