NAME

pthread_attr_getschedpolicy, pthread_attr_setschedpolicy — get and set the schedpolicy attribute (REALTIME THREADS)

SYNOPSIS

[TPS] #include <pthread.h>

int pthread_attr_getschedpolicy(const pthread_attr_t *restrict attr,
       int *restrict policy);
int pthread_attr_setschedpolicy(pthread_attr_t *attr, int policy);

DESCRIPTION

The pthread_attr_getschedpolicy() and pthread_attr_setschedpolicy() functions, respectively, shall get and set the schedpolicy attribute in the attr argument.

The supported values of policy shall include SCHED_FIFO, SCHED_RR, and SCHED_OTHER, which are defined in the <sched.h> header. When threads executing with the scheduling policy SCHED_FIFO, SCHED_RR, ^[TSP]  or SCHED_SPORADIC are waiting on a mutex, they shall acquire the mutex in priority order when the mutex is unlocked.

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

RETURN VALUE

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

ERRORS

The pthread_attr_setschedpolicy() function shall fail if:

[ENOTSUP]

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

The pthread_attr_setschedpolicy() function may fail if:

[EINVAL]

The value of policy 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_getschedpolicy() or pthread_attr_setschedpolicy() 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_getinheritsched, 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_getschedpolicy() and pthread_attr_setschedpolicy() 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 SCHED_SPORADIC scheduling policy is added for alignment with IEEE Std 1003.1d-1999.

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

IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/79 is applied, adding a reference to 2.9.4 Thread Scheduling in the APPLICATION USAGE section.

IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/80 is applied, updating the ERRORS section to include optional errors for the case when attr refers to an uninitialized thread attribute object.

Issue 7

The pthread_attr_getschedpolicy() and pthread_attr_setschedpolicy() 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/TC1-2008/0452 [314] is applied.

POSIX.1-2008, Technical Corrigendum 2, XSH/TC2-2008/0263 [757] is applied.