объект блокировки записи (write lock object)
Пролог (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.
Имя (Name)
pthread_rwlock_destroy, pthread_rwlock_init — destroy and
initialize a read-write lock object
Синопсис (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;
Описание (Description)
The pthread_rwlock_destroy() function shall destroy the read-
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 read-write lock results in
undefined behavior.
The pthread_rwlock_init() function shall allocate any resources
required to use the read-write lock referenced by rwlock and
initializes the lock to an unlocked state with attributes
referenced by attr. If 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
pthread_rwlock_init() is called specifying an already initialized
read-write lock. Results are undefined if a read-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 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 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 read-write lock attributes object.
Возвращаемое значение (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.
Ошибки (Error)
The pthread_rwlock_init() function shall fail if:
EAGAIN The system lacked the necessary resources (other than
memory) to initialize another read-write lock.
ENOMEM Insufficient memory exists to initialize the read-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.
Примеры (Examples)
None.
Использование в приложениях (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.1‐2017, Section 3.291, Priority
Inversion.
Обоснование (Rationale)
If an implementation detects that the value specified by the
rwlock argument to pthread_rwlock_destroy() does not refer to an
initialized read-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 read-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 read-write lock object,
or detects that the value specified by the rwlock argument to
pthread_rwlock_init() refers to an already initialized read-write
lock object, it is recommended that the function should fail and
report an [EBUSY] error.
Будущие направления (Future directions)
None.
Смотри также (See also)
pthread_rwlock_rdlock(3p), pthread_rwlock_timedrdlock(3p),
pthread_rwlock_timedwrlock(3p), pthread_rwlock_trywrlock(3p),
pthread_rwlock_unlock(3p)
The Base Definitions volume of POSIX.1‐2017, Section 3.291,
Priority Inversion, pthread.h(0p)
