PTHREAD_MUTEXATTR_GETTYPE(3C)PTHREAD_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 dead‐
lock. A thread attempting to relock this
mutex without first unlocking it will dead‐
lock. Attempting to unlock a mutex locked
by a different thread results in undefined
behavior. Attempting 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_PRI‐
VATE.
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
implementation 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.
Mar 23, 2005 PTHREAD_MUTEXATTR_GETTYPE(3C)
