PTHREAD_ATTR_INIT(3)
NAME
pthread_attr_init, pthread_attr_destroy, pthread_attr_set-
detachstate, pthread_attr_getdetachstate,
pthread_attr_setschedparam, pthread_attr_getschedparam,
pthread_attr_setschedpolicy, pthread_attr_getschedpolicy,
pthread_attr_setinheritsched, pthread_attr_getinher-
itsched, 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). Pass-
ing 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 immedi-
ately 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 inter-
preted 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 priori-
ties 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 argu-
ment.
ERRORS
The pthread_attr_setdetachstate function returns the fol-
lowing error codes on error:
EINVAL the specified detachstate is not one of
PTHREAD_CREATE_JOINABLE or PTHREAD_CRE-
ATE_DETACHED.
The pthread_attr_setschedparam function returns the fol-
lowing 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 fol-
lowing 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 fol-
lowing 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_PRO-
CESS.
ENOTSUP
the specified scope is PTHREAD_SCOPE_PROCESS
(not supported).
AUTHOR
Xavier Leroy lt;Xavier.Leroy@inria.fr
SEE ALSO
pthread_create(3) pthread_join(3) pthread_detach(3)
pthread_setschedparam(3).