PTHREAD_RWLOCK_DESTROY
Section: POSIX Programmer's Manual (3P)
Updated: 2017
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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_rwlock_destroy,
pthread_rwlock_init
- destroy and initialize a rea-write lock object
SYNOPSIS
#include <pthread.h>
int pthread_rwlock_destroy(pthread_rwlock_t *rwlock);
int pthread_rwlock_init(pthread_rwlock_t *restrict rwlock,
const pthread_rwlockattr_t *restrict attr);
pthread_rwlock_t rwlock = PTHREAD_RWLOCK_INITIALIZER;
DESCRIPTION
The
pthread_rwlock_destroy()
function shall destroy the rea-write lock object referenced by
rwlock
and release any resources used by the lock. The effect of subsequent
use of the lock is undefined until the lock is reinitialized by
another call to
pthread_rwlock_init().
An implementation may cause
pthread_rwlock_destroy()
to set the object referenced by
rwlock
to an invalid value. Results are undefined if
pthread_rwlock_destroy()
is called when any thread holds
rwlock.
Attempting to destroy an uninitialized rea-write lock results in
undefined behavior.
The
pthread_rwlock_init()
function shall allocate any resources required to use the rea-write
lock referenced by
rwlock
and initializes the lock to an unlocked state with attributes
referenced by
attr.
If
attr
is NULL, the default rea-write lock attributes shall be used; the
effect is the same as passing the address of a default rea-write lock
attributes object. Once initialized, the lock can be used any number of
times without being reinitialized. Results are undefined if
pthread_rwlock_init()
is called specifying an already initialized rea-write lock. Results
are undefined if a rea-write lock is used without first being
initialized.
If the
pthread_rwlock_init()
function fails,
rwlock
shall not be initialized and the contents of
rwlock
are undefined.
See
Section 2.9.9,
Synchronization Object Copies and Alternative Mappings
for further requirements.
In cases where default rea-write lock attributes are appropriate, the
macro PTHREAD_RWLOCK_INITIALIZER can be used to initialize rea-write
locks. The effect shall be equivalent to dynamic initialization by a
call to
pthread_rwlock_init()
with the
attr
parameter specified as NULL, except that no error checks are performed.
The behavior is undefined if the value specified by the
attr
argument to
pthread_rwlock_init()
does not refer to an initialized rea-write lock attributes object.
RETURN VALUE
If successful, the
pthread_rwlock_destroy()
and
pthread_rwlock_init()
functions shall return zero; otherwise, an error number shall be
returned to indicate the error.
ERRORS
The
pthread_rwlock_init()
function shall fail if:
- EAGAIN
-
The system lacked the necessary resources (other than memory) to
initialize another rea-write lock.
- ENOMEM
-
Insufficient memory exists to initialize the rea-write lock.
- EPERM
-
The caller does not have the privilege to perform the operation.
These functions shall not return an error code of
[EINTR].
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
Applications using these and related rea-write lock functions may be
subject to priority inversion, as discussed in the Base Definitions volume of POSIX.1-2017,
Section 3.291,
Priority Inversion.
RATIONALE
If an implementation detects that the value specified by the
rwlock
argument to
pthread_rwlock_destroy()
does not refer to an initialized rea-write lock object, it is
recommended that the function should fail and report an
[EINVAL]
error.
If an implementation detects that the value specified by the
attr
argument to
pthread_rwlock_init()
does not refer to an initialized rea-write lock attributes object,
it is recommended that the function should fail and report an
[EINVAL]
error.
If an implementation detects that the value specified by the
rwlock
argument to
pthread_rwlock_destroy()
or
pthread_rwlock_init()
refers to a locked rea-write lock object, or detects that the value
specified by the
rwlock
argument to
pthread_rwlock_init()
refers to an already initialized rea-write lock object, it is recommended
that the function should fail and report an
[EBUSY]
error.
FUTURE DIRECTIONS
None.
SEE ALSO
pthread_rwlock_rdlock(),
pthread_rwlock_timedrdlock(),
pthread_rwlock_timedwrlock(),
pthread_rwlock_trywrlock(),
pthread_rwlock_unlock()
The Base Definitions volume of POSIX.1-2017,
Section 3.291,
Priority Inversion,
<pthread.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.-2017, Standard for Information Technology- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 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 .
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/ma-pages/reporting_bugs.html .
Index
- PROLOG
-
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- EXAMPLES
-
- APPLICATION USAGE
-
- RATIONALE
-
- FUTURE DIRECTIONS
-
- SEE ALSO
-
- COPYRIGHT
-
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