Purpose
This function applies a read lock to the read-write lock specified by the argument rwlock. The calling thread acquires the read lock if a writer does not hold the lock and there are no writes blocked on the lock. Otherwise, the calling thread will not acquire the read lock. If the read lock is not acquired, the calling thread blocks (that is, it does not return from the f_pthread_rwlock_rdlock call) until it can acquire the lock. Results are undefined if the calling thread holds a write lock on rwlock at the time the call is made. A thread may hold multiple concurrent read locks on rwlock (that is, successfully call the f_pthread_rwlock_rdlock function n times). If so, the thread must perform matching unlocks (that is, it must call the f_pthread_rwlock_unlock function n times).
Class
Function
Argument Type and Attributes
Result Type and Attributes
INTEGER(4)
Result Value
On successful completion, this function returns 0. Otherwise, this function returns one of the following errors.