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man pages section 3: Basic Library Functions

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Updated: Friday, August 13, 2021



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


#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);


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.


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


The value specified by attr or pshared is invalid.


See attributes(7) for descriptions of the following attributes:

Interface Stability

See Also

pthread_rwlock_init(3C), pthread_rwlock_rdlock(3C), pthread_rwlock_unlock(3C), pthread_rwlock_wrlock(3C), , attributes(7), standards(7)


Previous releases of Oracle Solaris provided the PTHREAD_RWSCALE_PRIVATE_NP value of the process-shared attribute. This value is now deprecated but is still supported for source and binary compatibility. When passed to the pthread_rwlock_init() function, it is transformed into (PTHREAD_PROCESS_PRIVATE | PTHREAD_RWLOCK_SCALABLE_NP).