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PTHREAD_MUTEXATTR(3) Library Functions Manual PTHREAD_MUTEXATTR(3)
NAME
pthread_mutexattr_init, pthread_mutexattr_destroy,
pthread_mutexattr_setprioceiling, pthread_mutexattr_getprioceiling,
pthread_mutexattr_setprotocol, pthread_mutexattr_getprotocol,
pthread_mutexattr_settype, pthread_mutexattr_gettype,
pthread_mutexattr_getpshared, pthread_mutexattr_setpshared - mutex
attribute operations
LIBRARY
POSIX Threads Library (libpthread, -lpthread)
SYNOPSIS
#include <pthread.h>
int
pthread_mutexattr_init(pthread_mutexattr_t *attr);
int
pthread_mutexattr_destroy(pthread_mutexattr_t *attr);
int
pthread_mutexattr_setprioceiling(pthread_mutexattr_t *attr,
int prioceiling);
int
pthread_mutexattr_getprioceiling(pthread_mutexattr_t *attr,
int *prioceiling);
int
pthread_mutexattr_setprotocol(pthread_mutexattr_t *attr, int protocol);
int
pthread_mutexattr_getprotocol(pthread_mutexattr_t *attr, int *protocol);
int
pthread_mutexattr_settype(pthread_mutexattr_t *attr, int type);
int
pthread_mutexattr_gettype(pthread_mutexattr_t * restrict attr,
int * restrict type);
int
pthread_mutexattr_getpshared(const pthread_mutexattr_t * __restrict attr,
int * __restrict pshared);
int
pthread_mutexattr_setpshared(pthread_mutexattr_t * attr, int pshared);
DESCRIPTION
Mutex attributes are used to specify parameters to pthread_mutex_init().
Like with thread attributes, one attribute object can be used in multiple
calls to pthread_mutex_init(3), with or without modifications between
calls.
The pthread_mutexattr_init() function initializes attr with all the
default mutex attributes.
The pthread_mutexattr_destroy() function destroys attr.
The pthread_mutexattr_settype() functions set the mutex type value of the
attribute. Valid mutex types are:
PTHREAD_MUTEX_NORMAL
This type of mutex does not check for usage errors. It will
deadlock if reentered, and result in undefined behavior if a
locked mutex is unlocked by another thread. Attempts to unlock an
already unlocked PTHREAD_MUTEX_NORMAL mutex will result in
undefined behavior.
PTHREAD_MUTEX_ERRORCHECK
These mutexes do check for usage errors. If an attempt is made to
relock a PTHREAD_MUTEX_ERRORCHECK mutex without first dropping the
lock, an error will be returned. If a thread attempts to unlock a
PTHREAD_MUTEX_ERRORCHECK mutex that is locked by another thread,
an error will be returned. If a thread attempts to unlock a
PTHREAD_MUTEX_ERRORCHECK thread that is unlocked, an error will be
returned.
PTHREAD_MUTEX_RECURSIVE
These mutexes allow recursive locking. An attempt to relock a
PTHREAD_MUTEX_RECURSIVE mutex that is already locked by the same
thread succeeds. An equivalent number of pthread_mutex_unlock(3)
calls are needed before the mutex will wake another thread waiting
on this lock. If a thread attempts to unlock a
PTHREAD_MUTEX_RECURSIVE mutex that is locked by another thread, an
error will be returned. If a thread attempts to unlock a
PTHREAD_MUTEX_RECURSIVE thread that is unlocked, an error will be
returned.
It is advised that PTHREAD_MUTEX_RECURSIVE mutexes are not used
with condition variables. This is because of the implicit
unlocking done by pthread_cond_wait(3) and
pthread_cond_timedwait(3).
PTHREAD_MUTEX_DEFAULT
Also this type of mutex will cause undefined behavior if
reentered. Unlocking a PTHREAD_MUTEX_DEFAULT mutex locked by
another thread will result in undefined behavior. Attempts to
unlock an already unlocked PTHREAD_MUTEX_DEFAULT mutex will result
in undefined behavior.
This is the default mutex type for pthread_mutexattr_init().
The pthread_mutexattr_gettype() functions copy the type value of the
attribute to the location pointed to by the second parameter.
The pthread_mutexattr_getpshared() function obtains the value of the
process-shared attribute from the attributes object referenced by attr.
The pthread_mutexattr_setpshared() function is used to set the process-
shared attribute in an initialised attributes object referenced by attr.
The pthread_mutexattr_getprotocol() and pthread_mutexattr_setprotocol()
functions shall get and set the protocol attribute of a mutex attributes
object pointed to by attr which was previously created by the function
pthread_mutexattr_init().
The pthread_mutexattr_getprioceiling() and
pthread_mutexattr_setprioceiling() functions, shall get and set the
priority ceiling attribute of a mutex attributes object pointed to by
attr which was previously created by the function
pthread_mutexattr_init().
RETURN VALUES
If successful, these functions return 0. Otherwise, an error number is
returned to indicate the error.
ERRORS
The pthread_mutexattr_init() function shall fail if:
[ENOMEM] Insufficient memory exists to initialize the mutex
attributes object.
The pthread_mutexattr_settype() function shall fail if:
[EINVAL] The value specified either by type or attr is invalid.
No error numbers are defined for the pthread_mutexattr_destroy() and
pthread_mutexattr_gettype() functions.
pthread_mutexattr_setprioceiling() may fail if:
[EINVAL] Invalid value for attr, or invalid value for
prioceiling.
pthread_mutexattr_getprioceiling() may fail if:
[EINVAL] Invalid value for attr.
pthread_mutexattr_setprotocol() may fail if:
[EINVAL] Invalid value for attr, or invalid value for protocol.
pthread_mutexattr_getprotocol() may fail if:
[EINVAL] Invalid value for attr.
pthread_mutexattr_getpshared() and pthread_mutexattr_setpshared() may
fail if:
[EINVAL] the value specified by attr is invalid.
SEE ALSO
pthread_mutex_init(3)
STANDARDS
These functions conform to IEEE Std 1003.1-2001 ("POSIX.1").
BUGS
The pthread_mutexattr_getpshared() and pthread_mutexattr_setpshared()
functions are hidden by default since only thread shared attributes are
supported.
NetBSD 10.99 June 12, 2016 NetBSD 10.99