pthread_rwlock_rdlock(3)pthread_rwlock_rdlock(3)NAMEpthread_rwlock_rdlock - Acquires a read-write lock for read access
pthread_rwlock_t *rwlock );
DECthreads POSIX 1003.1c Library (libpthread.so)
Address of the read-write lock object to acquire for read access.
This routine acquires a read-write lock for read access. If no thread
already holds the lock for write access and there are no writers wait‐
ing to acquire the lock, the lock for read access is granted to the
calling thread and this routine returns. If a thread already holds the
lock for read access, the lock is granted and this routine returns.
A thread can hold multiple, concurrent locks for read access on the
same read-write lock. In a given thread, for each call to this routine
that successfully acquires the same read-write lock for read access, a
corresponding call to pthread_rwlock_unlock must be issued.
If some thread already holds the lock for write access, the calling
thread will not acquire the read lock. If the read lock is not
acquired, the calling thread blocks until it can acquire the lock for
read access. Results are undefined if the calling thread has already
acquired a lock for write access on rwlock when this routine is called.
If the read-write lock object referenced by rwlock is not initialized,
the results of calling this routine are undefined.
If a thread is interrupted (via a Tru64 UNIX signal or an OpenVMS AST)
while waiting for a read-write lock for read access, upon return from
the interrupt routine the thread resumes waiting for the lock as if it
had not been interrupted.
If an error condition occurs, this routine returns an integer value
indicating the type of error. Possible return values are as follows:
Successful completion. The lock for read access could not be acquired
because the maximum number of read lock acquisitions for rwlock has
been exceeded. The current thread already owns the read-write lock for
writing. The value specified by rwlock does not refer to an initial‐
ized read-write lock object.
Functions: pthread_rwlock_init(3), pthread_rwlockattr_init(3),
Manuals: Guide to DECthreads and Programmer's Guide