#### POSIX Threads for Windows – REFERENCE - Pthreads-w32

Reference Index

Table of Contents

## Name

pthread_attr_init, pthread_attr_destroy, pthread_attr_setdetachstate, pthread_attr_getdetachstate, pthread_attr_setschedparam, pthread_attr_getschedparam, pthread_attr_setschedpolicy, pthread_attr_getschedpolicy, pthread_attr_setinheritsched, pthread_attr_getinheritsched, pthread_attr_setscope, pthread_attr_getscope - thread creation attributes

## Synopsis

#include <pthread.h>

int pthread_attr_init(pthread_attr_t *attr);

int pthread_attr_destroy(pthread_attr_t *attr);

int pthread_attr_setdetachstate(pthread_attr_t *attr, int detachstate);

int pthread_attr_getdetachstate(const pthread_attr_t *attr, int *detachstate);

int pthread_attr_setschedpolicy(pthread_attr_t *attr, int policy);

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

int pthread_attr_setschedparam(pthread_attr_t *attr, const struct sched_param *param);

int pthread_attr_getschedparam(const pthread_attr_t *attr, struct sched_param *param);

int pthread_attr_setinheritsched(pthread_attr_t *attr, int inherit);

int pthread_attr_getinheritsched(const pthread_attr_t *attr, int *inherit);

int pthread_attr_setscope(pthread_attr_t *attr, int scope);

int pthread_attr_getscope(const pthread_attr_t *attr, int *scope);

## Description

Setting attributes for threads is achieved by filling a thread attribute object attr of type pthread_attr_t, then passing it as second argument to pthread_create(3) . Passing NULL is equivalent to passing a thread attribute object with all attributes set to their default values.

pthread_attr_init initializes the thread attribute object attr and fills it with default values for the attributes. (The default values are listed below for each attribute.)

Each attribute attrname (see below for a list of all attributes) can be individually set using the function pthread_attr_set attrname and retrieved using the function pthread_attr_get attrname.

pthread_attr_destroy destroys a thread attribute object, which must not then be reused until it is reinitialized.

Attribute objects are consulted only when creating a new thread. The same attribute object can be used for creating several threads. Modifying an attribute object after a call to pthread_create does not change the attributes of the thread previously created.

The following thread attributes are supported:

### detachstate

Control whether the thread is created in the joinable state (value PTHREAD_CREATE_JOINABLE) or in the detached state ( PTHREAD_CREATE_DETACHED).

Default value: PTHREAD_CREATE_JOINABLE.

In the joinable state, another thread can synchronize on the thread termination and recover its termination code using pthread_join(3) . When a joinable thread terminates, some of the thread resources are kept allocated, and released only when another thread performs pthread_join(3) on that thread.

In the detached state, the thread's resources are released immediately when it terminates. pthread_join(3) cannot be used to synchronize on the thread termination.

A thread created in the joinable state can later be put in the detached thread using pthread_detach(3) .

### schedpolicy

Select the scheduling policy for the thread: one of SCHED_OTHER (regular, non-real-time scheduling), SCHED_RR (real-time, round-robin) or SCHED_FIFO (real-time, first-in first-out).

Pthreads-w32 only supports SCHED_OTHER - attempting to set one of the other policies will return an error ENOTSUP.

Default value: SCHED_OTHER.

Pthreads-w32 only supports SCHED_OTHER - attempting to set one of the other policies will return an error ENOTSUP.

The scheduling policy of a thread can be changed after creation with pthread_setschedparam(3) .

### schedparam

Contain the scheduling parameters (essentially, the scheduling priority) for the thread.

Pthreads-w32 supports the priority levels defined by the Windows system it is running on. Under Windows, thread priorities are relative to the process priority class, which must be set via the Windows W32 API.

Default value: priority is 0 (Win32 level THREAD_PRIORITY_NORMAL).

The scheduling priority of a thread can be changed after creation with pthread_setschedparam(3) .

### inheritsched

Indicate whether the scheduling policy and scheduling parameters for the newly created thread are determined by the values of the schedpolicy and schedparam attributes (value PTHREAD_EXPLICIT_SCHED) or are inherited from the parent thread (value PTHREAD_INHERIT_SCHED).

Default value: PTHREAD_EXPLICIT_SCHED.

### scope

Define the scheduling contention scope for the created thread. The only value supported in the Pthreads-w32 implementation is PTHREAD_SCOPE_SYSTEM, meaning that the threads contend for CPU time with all processes running on the machine. The other value specified by the standard, PTHREAD_SCOPE_PROCESS, means that scheduling contention occurs only between the threads of the running process.

Pthreads-w32 only supports PTHREAD_SCOPE_SYSTEM.

Default value: PTHREAD_SCOPE_SYSTEM.

## Return Value

All functions return 0 on success and a non-zero error code on error. On success, the pthread_attr_get attrname functions also store the current value of the attribute attrname in the location pointed to by their second argument.

## Errors

The pthread_attr_setdetachstate function returns the following error codes on error:

EINVAL
  the specified detachstate is not one of PTHREAD_CREATE_JOINABLE or PTHREAD_CREATE_DETACHED.

The pthread_attr_setschedparam function returns the following error codes on error:

EINVAL
  the priority specified in param is outside the range of allowed priorities for the scheduling policy currently in attr (1 to 99 for SCHED_FIFO and SCHED_RR; 0 for SCHED_OTHER).

The pthread_attr_setschedpolicy function returns the following error codes on error:

EINVAL
  the specified policy is not one of SCHED_OTHER, SCHED_FIFO, or SCHED_RR.
ENOTSUP
  policy is not SCHED_OTHER, the only value supported by Pthreads-w32.

The pthread_attr_setinheritsched function returns the following error codes on error:

EINVAL
  the specified inherit is not one of PTHREAD_INHERIT_SCHED or PTHREAD_EXPLICIT_SCHED.

The pthread_attr_setscope function returns the following error codes on error:

EINVAL
  the specified scope is not one of PTHREAD_SCOPE_SYSTEM or PTHREAD_SCOPE_PROCESS.
ENOTSUP
  the specified scope is PTHREAD_SCOPE_PROCESS (not supported by Pthreads-w32).

## Author

Xavier Leroy <Xavier.Leroy@inria.fr>

Modified by Ross Johnson for use with Pthreads-w32.

## See Also

pthread_create(3) , pthread_join(3) , pthread_detach(3) , pthread_setschedparam(3) .

Table of Contents

- Name

- Synopsis

- Description

  - detachstate

  - schedpolicy

  - schedparam

  - inheritsched

  - scope

- Return Value

- Errors

- Author

- See Also