pthread_rwlockattr_getpshared

, pthread_rwlockattr_setpshared

- get or set process-shared attribute of read-write lock attributes object

Synopsis

cc –mt [ flag... ] file... [ library... ]
#include <pthread.h>

int pthread_rwlockattr_getpshared(
     const pthread_rwlockattr_t *restrict attr,
     int *restrict pshared);

int pthread_rwlockattr_setpshared(pthread_rwlockattr_t *attr,
     int pshared);

Description

The process-shared attribute is set to PTHREAD_PROCESS_SHARED to permit a read-write lock to be operated upon by any thread that has access to the memory where the read-write lock is allocated, even if the read-write lock is allocated in memory that is shared by multiple processes. If the process-shared attribute is PTHREAD_PROCESS_PRIVATE, the read-write lock will only be operated upon by threads created within the same process as the thread that initialised the read-write lock; if threads of differing processes attempt to operate on such a read-write lock, the behaviour is undefined. The default value of the process-shared attribute is PTHREAD_PROCESS_PRIVATE.

The pthread_rwlockattr_getpshared() function obtains the value of the process-shared attribute from the initialised attributes object referenced by attr. The pthread_rwlockattr_setpshared() function is used to set the process-shared attribute in an initialised attributes object referenced by attr.

Return Values

If successful, the pthread_rwlockattr_setpshared() function returns 0. Otherwise, an error number is returned to indicate the error.

Upon successful completion, the pthread_rwlockattr_getpshared() returns 0 and stores the value of the process-shared attribute of attr into the object referenced by the pshared parameter. Otherwise an error number is returned to indicate the error.

Errors

The pthread_rwlockattr_getpshared() and pthread_rwlockattr_setpshared() functions will fail if:

EINVAL

The value specified by attr or pshared is invalid.

Attributes

See attributes(5) for descriptions of the following attributes:

See Also

pthread_rwlock_init(3C), pthread_rwlock_rdlock(3C), pthread_rwlock_unlock(3C), pthread_rwlock_wrlock(3C), pthread_rwlockattr_init(3C), attributes(5), standards(5)