NAME

pthread_attr_getinheritsched, pthread_attr_setinheritsched — get and set the inheritsched attribute (REALTIME THREADS)

SYNOPSIS

[TPS] #include <pthread.h>

int pthread_attr_getinheritsched(const pthread_attr_t *restrict attr,
       int *restrict inheritsched);
int pthread_attr_setinheritsched(pthread_attr_t *attr,
       int inheritsched);

DESCRIPTION

The pthread_attr_getinheritsched() and pthread_attr_setinheritsched() functions, respectively, shall get and set the inheritsched attribute in the attr argument.

When the attributes objects are used by pthread_create(), the inheritsched attribute determines how the other scheduling attributes of the created thread shall be set.

The supported values of inheritsched shall be:

PTHREAD_INHERIT_SCHED

Specifies that the thread scheduling attributes shall be inherited from the creating thread, and the scheduling attributes in this attr argument shall be ignored.

PTHREAD_EXPLICIT_SCHED

Specifies that the thread scheduling attributes shall be set to the corresponding values from this attributes object.

The symbols PTHREAD_INHERIT_SCHED and PTHREAD_EXPLICIT_SCHED are defined in the <pthread.h> header.

The following thread scheduling attributes defined by POSIX.1-2024 are affected by the inheritsched attribute: scheduling policy (schedpolicy), scheduling parameters (schedparam), and scheduling contention scope (contentionscope).

The behavior is undefined if the value specified by the attr argument to pthread_attr_getinheritsched() or pthread_attr_setinheritsched() does not refer to an initialized thread attributes object.

RETURN VALUE

If successful, the pthread_attr_getinheritsched() and pthread_attr_setinheritsched() functions shall return zero; otherwise, an error number shall be returned to indicate the error.

ERRORS

The pthread_attr_setinheritsched() function shall fail if:

[ENOTSUP]

An attempt was made to set the attribute to an unsupported value.

The pthread_attr_setinheritsched() function may fail if:

[EINVAL]

The value of inheritsched is not valid.

These functions shall not return an error code of [EINTR].

EXAMPLES

None.

APPLICATION USAGE

After these attributes have been set, a thread can be created with the specified attributes using pthread_create(). Using these routines does not affect the current running thread.

See 2.9.4 Thread Scheduling for further details on thread scheduling attributes and their default settings.

RATIONALE

If an implementation detects that the value specified by the attr argument to pthread_attr_getinheritsched() or pthread_attr_setinheritsched() does not refer to an initialized thread attributes object, it is recommended that the function should fail and report an [EINVAL] error.

FUTURE DIRECTIONS

None.

SEE ALSO

pthread_attr_destroy, pthread_attr_getscope, pthread_attr_getschedpolicy, pthread_attr_getschedparam, pthread_create

XBD <pthread.h>, <sched.h>

CHANGE HISTORY

First released in Issue 5. Included for alignment with the POSIX Threads Extension.

Marked as part of the Realtime Threads Feature Group.

Issue 6

The pthread_attr_getinheritsched() and pthread_attr_setinheritsched() functions are marked as part of the Threads and Thread Execution Scheduling options.

The [ENOSYS] error condition has been removed as stubs need not be provided if an implementation does not support the Thread Execution Scheduling option.

The restrict keyword is added to the pthread_attr_getinheritsched() prototype for alignment with the ISO/IEC 9899:1999 standard.

IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/75 is applied, clarifying the values of inheritsched in the DESCRIPTION and adding two optional [EINVAL] errors to the ERRORS section for checking when attr refers to an uninitialized thread attribute object.

IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/77 is applied, adding a reference to 2.9.4 Thread Scheduling in the APPLICATION USAGE section.

Issue 7

The pthread_attr_getinheritsched() and pthread_attr_setinheritsched() functions are marked only as part of the Thread Execution Scheduling option as the Threads option is now part of the Base.

The [EINVAL] error for an uninitialized thread attributes object is removed; this condition results in undefined behavior.

POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0450 [314] is applied.

POSIX.1-2008, Technical Corrigendum 2, XSH/TC2-2008/0262 [757] is applied.