pthread_mutexattr_gettypeStandard C Library Functpthread_mutexattr_gettype(3C)NAME
pthread_mutexattr_gettype, pthread_mutexattr_settype - get or set mutex
type
SYNOPSIS
cc -mt [ flag... ] file... -lpthread [ library... ]
#include <pthread.h>
int pthread_mutexattr_gettype(pthread_mutexattr_t *restrict attr, int
*restrict type);
int pthread_mutexattr_settype(pthread_mutexattr_t *attr, int type);
DESCRIPTION
The pthread_mutexattr_gettype() and pthread_mutexattr_settype() func‐
tions respectively get and set the mutex type attribute. This attribute
is set in the type parameter to these functions. The default value of
the type attribute is PTHREAD_MUTEX_DEFAULT.
The type of mutex is contained in the type attribute of the mutex
attributes. Valid mutex types include:
PTHREAD_MUTEX_NORMAL This type of mutex does not detect
deadlock. A thread attempting to relock
this mutex without first unlocking it
will deadlock. Attempting to unlock a
mutex locked by a different thread
results in undefined behavior. Attempt‐
ing to unlock an unlocked mutex results
in undefined behavior.
PTHREAD_MUTEX_ERRORCHECK This type of mutex provides error
checking. A thread attempting to relock
this mutex without first unlocking it
will return with an error. A thread
attempting to unlock a mutex that
another thread has locked will return
with an error. A thread attempting to
unlock an unlocked mutex will return
with an error.
PTHREAD_MUTEX_RECURSIVE A thread attempting to relock this
mutex without first unlocking it will
succeed in locking the mutex. The
relocking deadlock that can occur with
mutexes of type PTHREAD_MUTEX_NORMAL
cannot occur with this type of mutex.
Multiple locks of this mutex require
the same number of unlocks to release
the mutex before another thread can
acquire the mutex. A thread attempting
to unlock a mutex that another thread
has locked will return with an error. A
thread attempting to unlock an unlocked
mutex will return with an error. This
type of mutex is only supported for
mutexes whose process shared attribute
is PTHREAD_PROCESS_PRIVATE.
PTHREAD_MUTEX_DEFAULT Attempting to recursively lock a mutex
of this type results in undefined
behavior. Attempting to unlock a mutex
of this type that was not locked by the
calling thread results in undefined
behavior. Attempting to unlock a mutex
of this type that is not locked results
in undefined behavior. An implementa‐
tion is allowed to map this mutex to
one of the other mutex types.
RETURN VALUES
Upon successful completion, the pthread_mutexattr_settype() function
returns 0. Otherwise, an error number is returned to indicate the
error.
Upon successful completion, the pthread_mutexattr_gettype() function
returns 0 and stores the value of the type attribute of attr in the
object referenced by the type parameter. Otherwise an error number is
returned to indicate the error.
ERRORS
The pthread_mutexattr_gettype() and pthread_mutexattr_settype() func‐
tions will fail if:
EINVAL The value type is invalid.
The pthread_mutexattr_gettype() and pthread_mutexattr_settype() func‐
tions may fail if:
EINVAL The value specified by attr is invalid.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Interface Stability │Standard │
├─────────────────────────────┼─────────────────────────────┤
│MT-Level │MT-Safe │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOpthread_cond_timedwait(3C), pthread_cond_wait(3C), attributes(5), stan‐
dards(5)NOTES
Application should not use a PTHREAD_MUTEX_RECURSIVE mutex with condi‐
tion variables because the implicit unlock performed for
pthread_cond_wait() or pthread_cond_timedwait() will not actually
release the mutex (if it had been locked multiple times). If this
occurs, no other thread can satisfy the condition of the predicate.
SunOS 5.10 23 Mar 2005 pthread_mutexattr_gettype(3C)
