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cc [options] -Kthread file#include <pthread.h>
int pthread_rwlock_init(pthread_rwlock_t *rwlock, const pthread_rwlockattr_t *attr);
int pthread_rwlock_destroy(pthread_rwlock_t *rwlock);
pthread_rwlock_t *rwlock=PTHREAD_RWLOCK_INITIALIZER
The rwlock parameter points to the reader-writer lock to be initialized or destroyed.
The attr parameter points to a read-write lock attributes object that will be used to initialize rwlock. If attr is NULL, the default read-write lock attributes are used; the effect is the same as passing the address of a default read-write attributes object.
If the pthread_rwlock_init function fails, rwlock is not initialized and its contents are undefined.
pthread_rwlock_destroy destroys the read-write object pointed to by rwlock and releases any resources used by the lock. This includes invalidating the lock and freeing any associated dynamically allocated resources. The effect of subsequent use of the lock is undefined until the lock is re-initialized by another call to pthread_rwlock_init. An implementation may cause pthread_rwlock_destroy to set the object referenced by rwlock to an invalid value. Results are undefined if pthread_rwlock_destroy is called when any thread holds rwlock. Attempting to destroy an uninitialized read-write lock results in undefined behavior. A destroyed read-write lock object can be re-initialized using pthread_rwlock_init; the results of otherwise referencing the read-write lock object after it has been destroyed are undefined.
pthread_rwlock_init returns the following value and does not change the contents of rwlock if the corresponding condition is detected:
pthread_rwlock_destroy returns the following values if the corresponding conditions are detected:
Most operations on read-write locks are not recursive--a thread can deadlock if it attempts to reacquire a read-write lock that it already has acquired.
Results are undefined if a read-write lock is used without first being initialized.