pthread_rwlock_destroy.3p (5947B)
- '\" et
- .TH PTHREAD_RWLOCK_DESTROY "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
- .\"
- .SH 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.
- .\"
- .SH NAME
- pthread_rwlock_destroy,
- pthread_rwlock_init
- \(em destroy and initialize a read-write lock object
- .SH SYNOPSIS
- .LP
- .nf
- #include <pthread.h>
- .P
- int pthread_rwlock_destroy(pthread_rwlock_t *\fIrwlock\fP);
- int pthread_rwlock_init(pthread_rwlock_t *restrict \fIrwlock\fP,
- const pthread_rwlockattr_t *restrict \fIattr\fP);
- pthread_rwlock_t \fIrwlock\fR = PTHREAD_RWLOCK_INITIALIZER;
- .fi
- .SH DESCRIPTION
- The
- \fIpthread_rwlock_destroy\fR()
- function shall destroy the read-write lock object referenced by
- .IR 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
- \fIpthread_rwlock_init\fR().
- An implementation may cause
- \fIpthread_rwlock_destroy\fR()
- to set the object referenced by
- .IR rwlock
- to an invalid value. Results are undefined if
- \fIpthread_rwlock_destroy\fR()
- is called when any thread holds
- .IR rwlock .
- Attempting to destroy an uninitialized read-write lock results in
- undefined behavior.
- .P
- The
- \fIpthread_rwlock_init\fR()
- function shall allocate any resources required to use the read-write
- lock referenced by
- .IR rwlock
- and initializes the lock to an unlocked state with attributes
- referenced by
- .IR attr .
- If
- .IR attr
- is NULL, the default read-write lock attributes shall be used; the
- effect is the same as passing the address of a default read-write lock
- attributes object. Once initialized, the lock can be used any number of
- times without being reinitialized. Results are undefined if
- \fIpthread_rwlock_init\fR()
- is called specifying an already initialized read-write lock. Results
- are undefined if a read-write lock is used without first being
- initialized.
- .P
- If the
- \fIpthread_rwlock_init\fR()
- function fails,
- .IR rwlock
- shall not be initialized and the contents of
- .IR rwlock
- are undefined.
- .P
- See
- .IR "Section 2.9.9" ", " "Synchronization Object Copies and Alternative Mappings"
- for further requirements.
- .P
- In cases where default read-write lock attributes are appropriate, the
- macro PTHREAD_RWLOCK_INITIALIZER can be used to initialize read-write
- locks. The effect shall be equivalent to dynamic initialization by a
- call to
- \fIpthread_rwlock_init\fR()
- with the
- .IR attr
- parameter specified as NULL, except that no error checks are performed.
- .P
- The behavior is undefined if the value specified by the
- .IR attr
- argument to
- \fIpthread_rwlock_init\fR()
- does not refer to an initialized read-write lock attributes object.
- .SH "RETURN VALUE"
- If successful, the
- \fIpthread_rwlock_destroy\fR()
- and
- \fIpthread_rwlock_init\fR()
- functions shall return zero; otherwise, an error number shall be
- returned to indicate the error.
- .SH ERRORS
- The
- \fIpthread_rwlock_init\fR()
- function shall fail if:
- .TP
- .BR EAGAIN
- The system lacked the necessary resources (other than memory) to
- initialize another read-write lock.
- .TP
- .BR ENOMEM
- Insufficient memory exists to initialize the read-write lock.
- .TP
- .BR EPERM
- The caller does not have the privilege to perform the operation.
- .P
- These functions shall not return an error code of
- .BR [EINTR] .
- .LP
- .IR "The following sections are informative."
- .SH EXAMPLES
- None.
- .SH "APPLICATION USAGE"
- Applications using these and related read-write lock functions may be
- subject to priority inversion, as discussed in the Base Definitions volume of POSIX.1\(hy2017,
- .IR "Section 3.291" ", " "Priority Inversion".
- .SH RATIONALE
- If an implementation detects that the value specified by the
- .IR rwlock
- argument to
- \fIpthread_rwlock_destroy\fR()
- does not refer to an initialized read-write lock object, it is
- recommended that the function should fail and report an
- .BR [EINVAL]
- error.
- .P
- If an implementation detects that the value specified by the
- .IR attr
- argument to
- \fIpthread_rwlock_init\fR()
- does not refer to an initialized read-write lock attributes object,
- it is recommended that the function should fail and report an
- .BR [EINVAL]
- error.
- .P
- If an implementation detects that the value specified by the
- .IR rwlock
- argument to
- \fIpthread_rwlock_destroy\fR()
- or
- \fIpthread_rwlock_init\fR()
- refers to a locked read-write lock object, or detects that the value
- specified by the
- .IR rwlock
- argument to
- \fIpthread_rwlock_init\fR()
- refers to an already initialized read-write lock object, it is recommended
- that the function should fail and report an
- .BR [EBUSY]
- error.
- .SH "FUTURE DIRECTIONS"
- None.
- .SH "SEE ALSO"
- .ad l
- .IR "\fIpthread_rwlock_rdlock\fR\^(\|)",
- .IR "\fIpthread_rwlock_timedrdlock\fR\^(\|)",
- .IR "\fIpthread_rwlock_timedwrlock\fR\^(\|)",
- .IR "\fIpthread_rwlock_trywrlock\fR\^(\|)",
- .IR "\fIpthread_rwlock_unlock\fR\^(\|)"
- .ad b
- .P
- The Base Definitions volume of POSIX.1\(hy2017,
- .IR "Section 3.291" ", " "Priority Inversion",
- .IR "\fB<pthread.h>\fP"
- .\"
- .SH COPYRIGHT
- Portions of this text are reprinted and reproduced in electronic form
- from IEEE Std 1003.1-2017, 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 .
- .PP
- 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/man-pages/reporting_bugs.html .