int
pthread_rwlock_rdlock(
pthread_rwlock_t *lock
)
int
pthread_rwlock_timedrdlock(
pthread_rwlock_t * restrict lock
, const struct timespec * restrict abstime
)
int
pthread_rwlock_tryrdlock(
pthread_rwlock_t *lock
)
)
function acquires a read lock on
lock
provided that
lock
is not presently held for writing and no writer threads are
presently blocked on the lock.
If the read lock cannot be immediately acquired, the calling thread
blocks until it can acquire the lock.
The
pthread_rwlock_timedrdlock()
performs the same action, but will not wait beyond
abstime
to obtain the lock before returning.
The
pthread_rwlock_tryrdlock()
function performs the same action as
pthread_rwlock_rdlock(
),
but does not block if the lock cannot be immediately obtained (i.e.,
the lock is held for writing or there are waiting writers).
A thread may hold multiple concurrent read locks.
If so,
pthread_rwlock_unlock()
must be called once for each lock obtained.
The results of acquiring a read lock while the calling thread holds a write lock are undefined.
),
pthread_rwlock_timedrdlock(
),
and
pthread_rwlock_tryrdlock(
)
functions will return zero.
Otherwise an error number will be returned to indicate the error.
)
function shall fail if:
EBUSY
]
The
pthread_rwlock_timedrdlock()
function shall fail if:
ETIMEDOUT
]
abstime
was reached before the lock could be obtained.
The
pthread_rwlock_rdlock(),
pthread_rwlock_timedrdlock(
),
and
pthread_rwlock_tryrdlock(
)
functions may fail if:
EAGAIN
]
lock
has been exceeded.
EDEADLK
]
lock
for writing.
EINVAL
]
lock
is invalid.
),
pthread_rwlock_timedrdlock(
),
and
pthread_rwlock_tryrdlock(
)
conform to
ISO/IEC 9945-1:1996 (``POSIX.1'') .