This version of this document is no longer maintained. For the latest documentation, see http://www.qnx.com/developers/docs.

pthread_rwlock_tryrdlock()

Attempt to acquire a shared lock on a read-write lock

Synopsis:

#include <pthread.h>

int pthread_rwlock_tryrdlock( 
                   pthread_rwlock_t* rwl );

Arguments:

rwl: A pointer to a pthread_rwlock_t object that you want to lock for reading.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

The pthread_rwlock_tryrdlock() function attempts to acquire a shared lock on the read-write lock referenced by rwl. If the read-write lock is already exclusively locked by any thread (including the calling thread), the function returns immediately instead of blocking until a read lock can be obtained.

Returns:

EOK: Success.
EAGAIN: On the first use of a statically initialized read-write lock, insufficient system resources existed to initialize the read-write lock.
EBUSY: The read-write lock was already write locked.
EDEADLK: The calling thread already has an exclusive lock for rwl.
EFAULT: A fault occurred when the kernel tried to access rwl.
EINVAL: The read-write lock rwl is invalid.

Classification:

POSIX 1003.1 THR

Safety:
Cancellation point	Yes
Interrupt handler	No
Signal handler	Yes
Thread	Yes