pthread_condattr_getpshared¶

Synopsis¶

#include <pthread.h>

int pthread_condattr_getpshared(const pthread_condattr_t *restrict attr,
                                int *restrict pshared);

int pthread_condattr_setpshared(pthread_condattr_t *attr, int pshared);

Status¶

Implemented

Conformance¶

IEEE Std 1003.1-2017

Description¶

The pthread_condattr_getpshared() function shall obtain the value of the process-shared attribute from the attributes object referenced by attr.

The pthread_condattr_setpshared() function shall set the process-shared attribute in an initialized attributes object referenced by attr.

The process-shared attribute is set to PTHREAD_PROCESS_SHARED to permit a condition variable to be operated upon by any thread that has access to the memory where the condition variable is allocated, even if the condition variable is allocated in memory that is shared by multiple processes. The default value of the attribute is PTHREAD_PROCESS_PRIVATE.

The behavior is undefined if the value specified by the attr argument to pthread_condattr_getpshared() or pthread_condattr_setpshared() does not refer to an initialized condition variable attributes object.

Return value¶

If successful, the pthread_condattr_setpshared() function shall return zero; otherwise, an error number shall be returned to indicate the error.

If successful, the pthread_condattr_getpshared() function shall return zero and store the value of the process-shared attribute of attr into the object referenced by the pshared parameter. Otherwise, an error number shall be returned to indicate the error.

Errors¶

The pthread_condattr_setpshared() function may fail if:

EINVAL - The new value specified for the attribute is outside the range of legal values for that attribute, or is PTHREAD_PROCESS_SHARED (see POSIX deviations).

These functions shall not return an error code of EINTR.

POSIX deviations¶

Phoenix-RTOS doesn’t support process-shared condition variables (the Thread Process-Shared Synchronization option, _POSIX_THREAD_PROCESS_SHARED is not defined). pthread_condattr_setpshared() fails with EINVAL when pshared is PTHREAD_PROCESS_SHARED, although it is a legal value of the attribute, so the attribute is always PTHREAD_PROCESS_PRIVATE. A Phoenix-RTOS condition variable is a kernel object identified by a handle which is valid only in the process that created it, so a condition variable placed in memory shared by several processes can’t be used by threads of the other processes.