pthread_mutexattr(3)
- NetBSD Manual Pages
PTHREAD_MUTEXATTR(3) NetBSD Library Functions Manual PTHREAD_MUTEXATTR(3)
NAME
pthread_mutexattr_init, pthread_mutexattr_destroy,
pthread_mutexattr_settype, pthread_mutexattr_gettype -- 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_settype(pthread_mutexattr_t *attr, int type);
int
pthread_mutexattr_gettype(pthread_mutexattr_t * restrict attr,
int * restrict type);
DESCRIPTION
Mutex attributes are used to specify parameters to pthread_mutex_init().
One attribute object can be used in multiple calls to
pthread_mutex_init(), 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,
PTHREAD_MUTEX_ERRORCHECK, PTHREAD_MUTEX_RECURSIVE, and
PTHREAD_MUTEX_DEFAULT. The default mutex type for
pthread_mutexaddr_init() is PTHREAD_MUTEX_DEFAULT.
PTHREAD_MUTEX_NORMAL mutexes do not check for usage errors.
PTHREAD_MUTEX_NORMAL mutexes 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 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 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.
PTHREAD_MUTEX_DEFAULT mutexes result in 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.
pthread_mutexattr_gettype() functions copy the type value of the
attribute to the location pointed to by the second parameter.
RETURN VALUES
If successful, these functions return 0. Otherwise, an error number is
returned to indicate the error.
ERRORS
pthread_mutexattr_init() shall fail if:
[ENOMEM] Insufficient memory exists to initialize the mutex
attributes object.
pthread_mutexattr_settype() shall fail if:
[EINVAL] The value specified by type is invalid.
pthread_mutexattr_destroy(), pthread_mutexattr_settype(), and
pthread_mutexattr_gettype() may fail if:
[EINVAL] Invalid value for attr.
SEE ALSO
pthread_mutex_init(3)
STANDARDS
pthread_mutexattr_init(), pthread_mutexattr_destroy(),
pthread_mutexattr_settype(), and pthread_mutexattr_gettype() conform to
ISO/IEC 9945-1:1996 (``POSIX.1'').
NetBSD 5.1 January 30, 2003 NetBSD 5.1
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