pthread_rwlock_tryrdlock() — Attempt to lock a read or write lock object for reading

Standards

Format

#define _OPEN_THREADS
#include <pthread.h>

int pthread_rwlock_tryrdlock(pthread_rwlock_t *rwlock);

#define _UNIX03_THREADS
#include <pthread.h>

int pthread_rwlock_tryrdlock(pthread_rwlock_t *rwlock);

General description

The pthread_rwlock_tryrdlock() function applies a read lock as in the pthread_rwlock_rdlock() function with the exception that the function fails if any thread holds a write lock on rwlock or there are writers blocked on rwlock unless the thread already held rwlock for read. Read/write locks are used to protect shared resources.

If the read or write lock identified by rwlock is locked, pthread_rwlock_tryrdlock() returns immediately.

When there are only read locks on the read or write lock, pthread_rwlock_tryrdlock() will effectively add to the count of the number of times pthread_rwlock_unlock() must be called by the thread to release the mutex (that is, it has the same behavior as a pthread_rwlock_rdlock() function).

Returned value

If successful, pthread_rwlock_tryrdlock() returns 0.

Special behavior for Single UNIX Specification, Version 3: If unsuccessful, pthread_rwlock_tryrdlock() returns an error number to indicate the error.

Related information

• pthread.h
• pthread_rwlock_destroy() — Destroy a read or write lock object
• pthread_rwlock_init() — Initialize a read or write lock object