mirror of git://sourceware.org/git/glibc.git
222 lines
7.2 KiB
Groff
222 lines
7.2 KiB
Groff
.TH PTHREAD_ATTR_INIT 3 LinuxThreads
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.XREF pthread_attr_destroy
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.XREF pthread_attr_setdetachstate
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.XREF pthread_attr_getdetachstate
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.XREF pthread_attr_setschedparam
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.XREF pthread_attr_getschedparam
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.XREF pthread_attr_setschedpolicy
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.XREF pthread_attr_getschedpolicy
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.XREF pthread_attr_setinheritsched
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.XREF pthread_attr_getinheritsched
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.XREF pthread_attr_setscope
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.XREF pthread_attr_getscope
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.SH NAME
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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
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.SH SYNOPSIS
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#include <pthread.h>
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int pthread_attr_init(pthread_attr_t *attr);
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int pthread_attr_destroy(pthread_attr_t *attr);
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int pthread_attr_setdetachstate(pthread_attr_t *attr, int detachstate);
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int pthread_attr_getdetachstate(const pthread_attr_t *attr, int *detachstate);
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int pthread_attr_setschedpolicy(pthread_attr_t *attr, int policy);
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int pthread_attr_getschedpolicy(const pthread_attr_t *attr, int *policy);
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int pthread_attr_setschedparam(pthread_attr_t *attr, const struct sched_param *param);
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int pthread_attr_getschedparam(const pthread_attr_t *attr, struct sched_param *param);
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int pthread_attr_setinheritsched(pthread_attr_t *attr, int inherit);
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int pthread_attr_getinheritsched(const pthread_attr_t *attr, int *inherit);
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int pthread_attr_setscope(pthread_attr_t *attr, int scope);
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int pthread_attr_getscope(const pthread_attr_t *attr, int *scope);
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.SH DESCRIPTION
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Setting attributes for threads is achieved by filling a
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thread attribute object |attr| of type !pthread_attr_t!, then passing it as
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second argument to !pthread_create!(3). Passing !NULL! is equivalent to
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passing a thread attribute object with all attributes set to their
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default values.
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!pthread_attr_init! initializes the thread attribute object |attr| and
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fills it with default values for the attributes. (The default values
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are listed below for each attribute.)
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Each attribute |attrname| (see below for a list of all attributes) can
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be individually set using the function !pthread_attr_set!|attrname|
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and retrieved using the function !pthread_attr_get!|attrname|.
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!pthread_attr_destroy! destroys a thread attribute object, which
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must not be reused until it is reinitialized. !pthread_attr_destroy!
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does nothing in the LinuxThreads implementation.
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Attribute objects are consulted only when creating a new thread. The
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same attribute object can be used for creating several
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threads. Modifying an attribute object after a call to
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!pthread_create! does not change the attributes of the thread
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previously created.
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The following thread attributes are supported:
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.SS detachstate
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Control whether the thread is created in the joinable state (value
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!PTHREAD_CREATE_JOINABLE!) or in the detached state
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(!PTHREAD_CREATE_DETACHED!).
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Default value: !PTHREAD_CREATE_JOINABLE!.
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In the joinable state, another thread can synchronize on the thread
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termination and recover its termination code using !pthread_join!(3),
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but some of the thread resources are kept allocated after the thread
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terminates, and reclaimed only when another thread performs
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!pthread_join!(3) on that thread.
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In the detached state, the thread resources are immediately freed when
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it terminates, but !pthread_join!(3) cannot be used to synchronize on
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the thread termination.
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A thread created in the joinable state can later be put in the
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detached thread using !pthread_detach!(3).
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.SS schedpolicy
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Select the scheduling policy for the thread: one of
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!SCHED_OTHER! (regular, non-realtime scheduling),
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!SCHED_RR! (realtime, round-robin) or
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!SCHED_FIFO! (realtime, first-in first-out). See
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!sched_setpolicy!(2) for more information on scheduling policies.
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Default value: !SCHED_OTHER!.
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The realtime scheduling policies !SCHED_RR! and !SCHED_FIFO! are
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available only to processes with superuser privileges.
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The scheduling policy of a thread can be changed after creation with
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!pthread_setschedparam!(3).
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.SS schedparam
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Contain the scheduling parameters (essentially, the scheduling
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priority) for the thread. See !sched_setparam!(2) for more information
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on scheduling parameters.
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Default value: priority is 0.
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This attribute is not significant if the scheduling policy is !SCHED_OTHER!;
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it only matters for the realtime policies !SCHED_RR! and !SCHED_FIFO!.
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The scheduling priority of a thread can be changed after creation with
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!pthread_setschedparam!(3).
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.SS inheritsched
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Indicate whether the scheduling policy and scheduling parameters for
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the newly created thread are determined by the values of the
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|schedpolicy| and |schedparam| attributes (value
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!PTHREAD_EXPLICIT_SCHED!) or are inherited from the parent thread
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(value !PTHREAD_INHERIT_SCHED!).
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Default value: !PTHREAD_EXPLICIT_SCHED!.
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.SS scope
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Define the scheduling contention scope for the created thread. The
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only value supported in the LinuxThreads implementation is
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!PTHREAD_SCOPE_SYSTEM!, meaning that the threads contend for CPU time
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with all processes running on the machine. In particular, thread
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priorities are interpreted relative to the priorities of all other
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processes on the machine. The other value specified by the standard,
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!PTHREAD_SCOPE_PROCESS!, means that scheduling contention occurs only
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between the threads of the running process: thread priorities are
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interpreted relative to the priorities of the other threads of the
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process, regardless of the priorities of other processes.
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!PTHREAD_SCOPE_PROCESS! is not supported in LinuxThreads.
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Default value: !PTHREAD_SCOPE_SYSTEM!.
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.SH "RETURN VALUE"
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All functions return 0 on success and a non-zero error code on error.
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On success, the !pthread_attr_get!|attrname| functions also store the
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current value of the attribute |attrname| in the location pointed to
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by their second argument.
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.SH ERRORS
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The !pthread_attr_setdetachstate! function returns the following error
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codes on error:
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.RS
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.TP
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!EINVAL!
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the specified |detachstate| is not one of !PTHREAD_CREATE_JOINABLE! or
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!PTHREAD_CREATE_DETACHED!.
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.RE
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The !pthread_attr_setschedparam! function returns the following error
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codes on error:
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.RS
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.TP
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!EINVAL!
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the priority specified in |param| is outside the range of allowed
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priorities for the scheduling policy currently in |attr|
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(1 to 99 for !SCHED_FIFO! and !SCHED_RR!; 0 for !SCHED_OTHER!).
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.RE
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The !pthread_attr_setschedpolicy! function returns the following error
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codes on error:
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.RS
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.TP
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!EINVAL!
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the specified |policy| is not one of !SCHED_OTHER!, !SCHED_FIFO!, or
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!SCHED_RR!.
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.TP
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!ENOTSUP!
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|policy| is !SCHED_FIFO! or !SCHED_RR!, and the effective user of the
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calling process is not super-user.
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.RE
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The !pthread_attr_setinheritsched! function returns the following error
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codes on error:
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.RS
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.TP
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!EINVAL!
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the specified |inherit| is not one of !PTHREAD_INHERIT_SCHED! or
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!PTHREAD_EXPLICIT_SCHED!.
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.RE
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The !pthread_attr_setscope! function returns the following error
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codes on error:
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.RS
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.TP
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!EINVAL!
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the specified |scope| is not one of !PTHREAD_SCOPE_SYSTEM! or
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!PTHREAD_SCOPE_PROCESS!.
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.TP
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!ENOTSUP!
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the specified |scope| is !PTHREAD_SCOPE_PROCESS! (not supported).
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.RE
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.SH AUTHOR
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Xavier Leroy <Xavier.Leroy@inria.fr>
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.SH "SEE ALSO"
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!pthread_create!(3),
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!pthread_join!(3),
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!pthread_detach!(3),
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!pthread_setschedparam!(3).
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