pthread_attr_getschedparam
PTHREAD_ATTR_INIT(3) 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 *pol-
icy);
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 val-
ues.
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. Modify-
ing 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_CRE-
ATE_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 termi-
nates, 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 (regu-
lar, 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 prior-
ity) 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 schedpol-
icy 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 prior-
ities 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 pro-
cess, 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 cur-
rent 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_CRE-
ATE_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 sup-
ported).
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)
