pthread_attr_init, pthread_attr_destroy, pthread_attr_setdetachstate, pthread_attr_getde-
tachstate, pthread_attr_setschedparam, pthread_attr_getschedparam, pthread_attr_setsched-
policy, pthread_attr_getschedpolicy, pthread_attr_setinheritsched, pthread_attr_getinher-
itsched, pthread_attr_setscope, pthread_attr_getscope - thread creation attributes
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);
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
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_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:
Control whether the thread is created in the joinable state (value PTHREAD_CREATE_JOIN-
ABLE) 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 per-
forms 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
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_setsched-
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_setsched-
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
Default value: PTHREAD_EXPLICIT_SCHED.
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 con-
tend for CPU time with all processes running on the machine. In particular, thread priori-
ties 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 con-
tention 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 Linux-
Default value: PTHREAD_SCOPE_SYSTEM.
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.
The pthread_attr_setdetachstate function returns the following error codes on error:
EINVAL the specified detachstate is not one of PTHREAD_CREATE_JOINABLE or
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.
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
The pthread_attr_setscope function returns the following error codes on error:
EINVAL the specified scope is not one of PTHREAD_SCOPE_SYSTEM or
the specified scope is PTHREAD_SCOPE_PROCESS (not supported).
Xavier Leroy <Xavier.Leroy@inria.fr>
pthread_create(3), pthread_join(3), pthread_detach(3), pthread_setschedparam(3).