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Acquire a shared read lock on a read-write lock
#include <pthread.h> int pthread_rwlock_rdlock( pthread_rwlock_t* rwl );
- A pointer to a pthread_rwlock_t object that you want to lock for reading.
Use the -l c option to qcc to link against this library. This library is usually included automatically.
The pthread_rwlock_rdlock() function acquires a shared lock on the read-write lock referenced by rwl. If the read-write lock is already exclusively locked, the calling thread blocks until the exclusive lock is released.
If a signal is delivered to a thread waiting to lock a read-write lock, it will resume waiting for the lock after returning from the signal handler.
A thread may hold several read locks on the same read-write lock; it must call pthread_rwlock_unlock() multiple times to release its read lock.
- On the first use of statically initialized read-write lock, insufficient system resources existed to initialize the read-write lock.
- The calling thread already has an exclusive lock for rwl.
- A fault occurred when the kernel tried to access rwl.
- The read-write lock rwl is invalid.