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PTHREAD_MUTEXATTR_GETTYPE
Section: POSIX Programmer's Manual (3P)
Updated: 2003
Index
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PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
NAME
pthread_mutexattr_gettype, pthread_mutexattr_settype - get and set
the mutex type attribute
SYNOPSIS
#include <pthread.h>
int pthread_mutexattr_gettype(const 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()
functions, respectively, shall 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 shall deadlock.
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 shall return with
an error. A thread attempting to unlock a mutex which another thread
has locked shall return with an error. A thread attempting to
unlock an unlocked mutex shall return with an error.
- PTHREAD_MUTEX_RECURSIVE
-
A thread attempting to relock this mutex without first unlocking it
shall succeed in locking the mutex. The relocking deadlock
which can occur with mutexes of type PTHREAD_MUTEX_NORMAL cannot occur
with this type of mutex. Multiple locks of this mutex shall
require the same number of unlocks to release the mutex before another
thread can acquire the mutex. A thread attempting to unlock
a mutex which another thread has locked shall return with an error.
A thread attempting to unlock an unlocked mutex shall return
with an error.
- PTHREAD_MUTEX_DEFAULT
-
Attempting to recursively lock a mutex of this type results in undefined
behavior. Attempting to unlock a mutex of this type which
was not locked by the calling thread results in undefined behavior.
Attempting to unlock a mutex of this type which is not locked
results in undefined behavior. An implementation may map this mutex
to one of the other mutex types.
RETURN VALUE
Upon successful completion, the pthread_mutexattr_gettype()
function shall return zero and store the value of the
type attribute of attr into the object referenced by the
type parameter. Otherwise, an error shall be returned
to indicate the error.
If successful, the pthread_mutexattr_settype() function shall
return zero; otherwise, an error number shall be returned
to indicate the error.
ERRORS
The pthread_mutexattr_settype() function shall fail if:
- EINVAL
-
The value type is invalid.
The pthread_mutexattr_gettype() and pthread_mutexattr_settype()
functions may fail if:
- EINVAL
-
The value specified by attr is invalid.
These functions shall not return an error code of [EINTR].
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
It is advised that an application should not use a PTHREAD_MUTEX_RECURSIVE
mutex with condition variables because the implicit
unlock performed for a pthread_cond_timedwait() or pthread_cond_wait()
may not actually release the mutex (if it had been locked
multiple times). If this happens, no other thread can satisfy the
condition of the predicate.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
pthread_cond_timedwait(), the Base Definitions volume of
IEEE Std 1003.1-2001, <pthread.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
Index
- PROLOG
-
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- EXAMPLES
-
- APPLICATION USAGE
-
- RATIONALE
-
- FUTURE DIRECTIONS
-
- SEE ALSO
-
- COPYRIGHT
-
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