блокировка записи для чтения (write lock for reading)
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_timedrdlock — lock a read-write lock for reading
Синопсис (Synopsis)
#include <pthread.h>
#include <time.h>
int pthread_rwlock_timedrdlock(pthread_rwlock_t *restrict rwlock,
const struct timespec *restrict abstime);
Описание (Description)
The pthread_rwlock_timedrdlock() function shall apply a read lock
to the read-write lock referenced by rwlock as in the
pthread_rwlock_rdlock() function. However, if the lock cannot be
acquired without waiting for other threads to unlock the lock,
this wait shall be terminated when the specified timeout expires.
The timeout shall expire when the absolute time specified by
abstime passes, as measured by the clock on which timeouts are
based (that is, when the value of that clock equals or exceeds
abstime), or if the absolute time specified by abstime has
already been passed at the time of the call.
The timeout shall be based on the CLOCK_REALTIME clock. The
resolution of the timeout shall be the resolution of the
CLOCK_REALTIME clock. The timespec data type is defined in the
<time.h> header. Under no circumstances shall the function fail
with a timeout if the lock can be acquired immediately. The
validity of the abstime parameter need not be checked if the lock
can be immediately acquired.
If a signal that causes a signal handler to be executed is
delivered to a thread blocked on a read-write lock via a call to
pthread_rwlock_timedrdlock(), upon return from the signal handler
the thread shall resume waiting for the lock as if it was not
interrupted.
The calling thread may deadlock if at the time the call is made
it holds a write lock on rwlock. The results are undefined if
this function is called with an uninitialized read-write lock.
Возвращаемое значение (Return value)
The pthread_rwlock_timedrdlock() function shall return zero if
the lock for reading on the read-write lock object referenced by
rwlock is acquired. Otherwise, an error number shall be returned
to indicate the error.
Ошибки (Error)
The pthread_rwlock_timedrdlock() function shall fail if:
ETIMEDOUT
The lock could not be acquired before the specified
timeout expired.
The pthread_rwlock_timedrdlock() function may fail if:
EAGAIN The read lock could not be acquired because the maximum
number of read locks for lock would be exceeded.
EDEADLK
A deadlock condition was detected or the calling thread
already holds a write lock on rwlock.
EINVAL The abstime nanosecond value is less than zero or greater
than or equal to 1000 million.
This function shall not return an error code of [EINTR].
The following sections are informative.
Примеры (Examples)
None.
Использование в приложениях (Application usage)
Applications using this function 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_timedrdlock() does not refer to
an initialized read-write lock object, it is recommended that the
function should fail and report an [EINVAL] error.
Будущие направления (Future directions)
None.
Смотри также (See also)
pthread_rwlock_destroy(3p), pthread_rwlock_rdlock(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, Section 4.12, Memory Synchronization,
pthread.h(0p), time.h(0p)
