pthread_attr_init

PTHREAD_ATTR_INIT(3)       Library Functions Manual       PTHREAD_ATTR_INIT(3)



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_setattrname and
       retrieved using the function pthread_attr_getattrname.

       pthread_attr_destroy destroys a thread attribute object, which must not
       be reused until it is reinitialized.  pthread_attr_destroy does nothing
       in the LinuxThreads implementation.

       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), but
       some of the thread resources are kept allocated after the thread
       terminates, and reclaimed only when another thread performs
       pthread_join(3) on that thread.

       In the detached state, the thread resources are immediately freed when
       it terminates, but 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-realtime scheduling), SCHED_RR (realtime, round-robin) or
       SCHED_FIFO (realtime, first-in first-out). See sched_setpolicy(2) for
       more information on scheduling policies.

       Default value: SCHED_OTHER.

       The realtime scheduling policies SCHED_RR and SCHED_FIFO are available
       only to processes with superuser privileges.

       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. See sched_setparam(2) for more information on
       scheduling parameters.

       Default value: priority is 0.

       This attribute is not significant if the scheduling policy is
       SCHED_OTHER; it only matters for the realtime policies SCHED_RR and
       SCHED_FIFO.

       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 LinuxThreads implementation is
       PTHREAD_SCOPE_SYSTEM, meaning that the threads contend for CPU time
       with all processes running on the machine. In particular, thread
       priorities are interpreted relative to the priorities of all other
       processes 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: thread priorities are
       interpreted relative to the priorities of the other threads of the
       process, regardless of the priorities of other processes.
       PTHREAD_SCOPE_PROCESS is not supported in LinuxThreads.

       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_getattrname 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 SCHED_FIFO or SCHED_RR, and the effective user
                     of the calling process is not super-user.

       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).


AUTHOR
       Xavier Leroy <Xavier.Leroy@inria.fr>


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



                                 LinuxThreads             PTHREAD_ATTR_INIT(3)