freebsd/share/man/man3/pthread.3

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.Dd January 15, 2004
.Dt PTHREAD 3
.Os
.Sh NAME
.Nm pthread
.Nd POSIX thread functions
.Sh LIBRARY
.Lb libpthread
.Lb libthr
.Sh SYNOPSIS
.In pthread.h
.Sh DESCRIPTION
POSIX threads are a set of functions that support applications with
requirements for multiple flows of control, called
.Em threads ,
within a process.
Multithreading is used to improve the performance of a
program.
.Pp
The POSIX thread functions are summarized in this section in the following
groups:
.Pp
.Bl -bullet -offset indent -compact
.It
Thread Routines
.It
Attribute Object Routines
.It
Mutex Routines
.It
Condition Variable Routines
.It
Read/Write Lock Routines
.It
Per-Thread Context Routines
.It
Cleanup Routines
.El
.Ss Thread Routines
.Bl -tag -width indent
.It Xo
.Ft int
.Fo pthread_create
.Fa "pthread_t *thread" "const pthread_attr_t *attr"
.Fa "void *\*[lp]*start_routine\*[rp]\*[lp]void *\*[rp]" "void *arg"
.Fc
.Xc
Creates a new thread of execution.
.It Xo
.Ft int
.Fn pthread_cancel "pthread_t thread"
.Xc
Cancels execution of a thread.
.It Xo
.Ft int
.Fn pthread_detach "pthread_t thread"
.Xc
Marks a thread for deletion.
.It Xo
.Ft int
.Fn pthread_equal "pthread_t t1" "pthread_t t2"
.Xc
Compares two thread IDs.
.It Xo
.Ft void
.Fn pthread_exit "void *value_ptr"
.Xc
Terminates the calling thread.
.It Xo
.Ft int
.Fn pthread_join "pthread_t thread" "void **value_ptr"
.Xc
Causes the calling thread to wait for the termination of the specified thread.
.It Xo
.Ft int
.Fn pthread_kill "pthread_t thread" "int sig"
.Xc
Delivers a signal to a specified thread.
.It Xo
.Ft int
.Fn pthread_once "pthread_once_t *once_control" "void \*[lp]*init_routine\*[rp]\*[lp]void\*[rp]"
.Xc
Calls an initialization routine once.
.It Xo
.Ft pthread_t
.Fn pthread_self void
.Xc
Returns the thread ID of the calling thread.
.It Xo
.Ft int
.Fn pthread_setcancelstate "int state" "int *oldstate"
.Xc
Sets the current thread's cancelability state.
.It Xo
.Ft int
.Fn pthread_setcanceltype "int type" "int *oldtype"
.Xc
Sets the current thread's cancelability type.
.It Xo
.Ft void
.Fn pthread_testcancel void
.Xc
Creates a cancellation point in the calling thread.
.It Xo
.Ft void
.Fn pthread_yield void
.Xc
Allows the scheduler to run another thread instead of the current one.
.El
.Ss Attribute Object Routines
.Bl -tag -width indent
.It Xo
.Ft int
.Fn pthread_attr_destroy "pthread_attr_t *attr"
.Xc
Destroy a thread attributes object.
.It Xo
.Ft int
.Fo pthread_attr_getinheritsched
.Fa "const pthread_attr_t *attr" "int *inheritsched"
.Fc
.Xc
Get the inherit scheduling attribute from a thread attributes object.
.It Xo
.Ft int
.Fo pthread_attr_getschedparam
.Fa "const pthread_attr_t *attr" "struct sched_param *param"
.Fc
.Xc
Get the scheduling parameter attribute from a thread attributes object.
.It Xo
.Ft int
.Fn pthread_attr_getschedpolicy "const pthread_attr_t *attr" "int *policy"
.Xc
Get the scheduling policy attribute from a thread attributes object.
.It Xo
.Ft int
.Fn pthread_attr_getscope "const pthread_attr_t *attr" "int *contentionscope"
.Xc
Get the contention scope attribute from a thread attributes object.
.It Xo
.Ft int
.Fn pthread_attr_getstacksize "const pthread_attr_t *attr" "size_t *stacksize"
.Xc
Get the stack size attribute from a thread attributes object.
.It Xo
.Ft int
.Fn pthread_attr_getstackaddr "const pthread_attr_t *attr" "void **stackaddr"
.Xc
Get the stack address attribute from a thread attributes object.
.It Xo
.Ft int
.Fn pthread_attr_getdetachstate "const pthread_attr_t *attr" "int *detachstate"
.Xc
Get the detach state attribute from a thread attributes object.
.It Xo
.Ft int
.Fn pthread_attr_init "pthread_attr_t *attr"
.Xc
Initialize a thread attributes object with default values.
.It Xo
.Ft int
.Fn pthread_attr_setinheritsched "pthread_attr_t *attr" "int inheritsched"
.Xc
Set the inherit scheduling attribute in a thread attributes object.
.It Xo
.Ft int
.Fo pthread_attr_setschedparam
.Fa "pthread_attr_t *attr" "const struct sched_param *param"
.Fc
.Xc
Set the scheduling parameter attribute in a thread attributes object.
.It Xo
.Ft int
.Fn pthread_attr_setschedpolicy "pthread_attr_t *attr" "int policy"
.Xc
Set the scheduling policy attribute in a thread attributes object.
.It Xo
.Ft int
.Fn pthread_attr_setscope "pthread_attr_t *attr" "int contentionscope"
.Xc
Set the contention scope attribute in a thread attributes object.
.It Xo
.Ft int
.Fn pthread_attr_setstacksize "pthread_attr_t *attr" "size_t stacksize"
.Xc
Set the stack size attribute in a thread attributes object.
.It Xo
.Ft int
.Fn pthread_attr_setstackaddr "pthread_attr_t *attr" "void *stackaddr"
.Xc
Set the stack address attribute in a thread attributes object.
.It Xo
.Ft int
.Fn pthread_attr_setdetachstate "pthread_attr_t *attr" "int detachstate"
.Xc
Set the detach state in a thread attributes object.
.El
.Ss Mutex Routines
.Bl -tag -width indent
.It Xo
.Ft int
.Fn pthread_mutexattr_destroy "pthread_mutexattr_t *attr"
.Xc
Destroy a mutex attributes object.
.It Xo
.Ft int
.Fn pthread_mutexattr_getprioceiling "pthread_mutexattr_t *attr" "int *ceiling"
.Xc
Obtain priority ceiling attribute of mutex attribute object.
.It Xo
.Ft int
.Fn pthread_mutexattr_getprotocol "pthread_mutexattr_t *attr" "int *protocol"
.Xc
Obtain protocol attribute of mutex attribute object.
.It Xo
.Ft int
.Fn pthread_mutexattr_gettype "pthread_mutexattr_t *attr" "int *type"
.Xc
Obtain the mutex type attribute in the specified mutex attributes object.
.It Xo
.Ft int
.Fn pthread_mutexattr_init "pthread_mutexattr_t *attr"
.Xc
Initialize a mutex attributes object with default values.
.It Xo
.Ft int
.Fn pthread_mutexattr_setprioceiling "pthread_mutexattr_t *attr" "int ceiling"
.Xc
Set priority ceiling attribute of mutex attribute object.
.It Xo
.Ft int
.Fn pthread_mutexattr_setprotocol "pthread_mutexattr_t *attr" "int protocol"
.Xc
Set protocol attribute of mutex attribute object.
.It Xo
.Ft int
.Fn pthread_mutexattr_settype "pthread_mutexattr_t *attr" "int type"
.Xc
Set the mutex type attribute that is used when a mutex is created.
.It Xo
.Ft int
.Fn pthread_mutex_destroy "pthread_mutex_t *mutex"
.Xc
Destroy a mutex.
.It Xo
.Ft int
.Fo pthread_mutex_init
.Fa "pthread_mutex_t *mutex" "const pthread_mutexattr_t *attr"
.Fc
.Xc
Initialize a mutex with specified attributes.
.It Xo
.Ft int
.Fn pthread_mutex_lock "pthread_mutex_t *mutex"
.Xc
Lock a mutex and block until it becomes available.
.It Xo
.Ft int
.Fo pthread_mutex_timedlock
.Fa "pthread_mutex_t *mutex" "const struct timespec *abstime"
.Fc
.Xc
Lock a mutex and block until it becomes available or until the timeout expires.
.It Xo
.Ft int
.Fn pthread_mutex_trylock "pthread_mutex_t *mutex"
.Xc
Try to lock a mutex, but do not block if the mutex is locked by another thread,
including the current thread.
.It Xo
.Ft int
.Fn pthread_mutex_unlock "pthread_mutex_t *mutex"
.Xc
Unlock a mutex.
.El
.Ss Condition Variable Routines
.Bl -tag -width indent
.It Xo
.Ft int
.Fn pthread_condattr_destroy "pthread_condattr_t *attr"
.Xc
Destroy a condition variable attributes object.
.It Xo
.Ft int
.Fn pthread_condattr_init "pthread_condattr_t *attr"
.Xc
Initialize a condition variable attributes object with default values.
.It Xo
.Ft int
.Fn pthread_cond_broadcast "pthread_cond_t *cond"
.Xc
Unblock all threads currently blocked on the specified condition variable.
.It Xo
.Ft int
.Fn pthread_cond_destroy "pthread_cond_t *cond"
.Xc
Destroy a condition variable.
.It Xo
.Ft int
.Fn pthread_cond_init "pthread_cond_t *cond" "const pthread_condattr_t *attr"
.Xc
Initialize a condition variable with specified attributes.
.It Xo
.Ft int
.Fn pthread_cond_signal "pthread_cond_t *cond"
.Xc
Unblock at least one of the threads blocked on the specified condition variable.
.It Xo
.Ft int
.Fo pthread_cond_timedwait
.Fa "pthread_cond_t *cond" "pthread_mutex_t *mutex"
.Fa "const struct timespec *abstime"
.Fc
.Xc
Wait no longer than the specified time for a condition
and lock the specified mutex.
.It Xo
.Ft int
.Fn pthread_cond_wait "pthread_cond_t *" "pthread_mutex_t *mutex"
.Xc
Wait for a condition and lock the specified mutex.
.El
.Ss Read/Write Lock Routines
.Bl -tag -width indent
.It Xo
.Ft int
.Fn pthread_rwlock_destroy "pthread_rwlock_t *lock"
.Xc
Destroy a read/write lock object.
.It Xo
.Ft int
.Fo pthread_rwlock_init
.Fa "pthread_rwlock_t *lock" "const pthread_rwlockattr_t *attr"
.Fc
.Xc
Initialize a read/write lock object.
.It Xo
.Ft int
.Fn pthread_rwlock_rdlock "pthread_rwlock_t *lock"
.Xc
Lock a read/write lock for reading, blocking until the lock can be
acquired.
.It Xo
.Ft int
.Fn pthread_rwlock_tryrdlock "pthread_rwlock_t *lock"
.Xc
Attempt to lock a read/write lock for reading, without blocking if the
lock is unavailable.
.It Xo
.Ft int
.Fn pthread_rwlock_trywrlock "pthread_rwlock_t *lock"
.Xc
Attempt to lock a read/write lock for writing, without blocking if the
lock is unavailable.
.It Xo
.Ft int
.Fn pthread_rwlock_unlock "pthread_rwlock_t *lock"
.Xc
Unlock a read/write lock.
.It Xo
.Ft int
.Fn pthread_rwlock_wrlock "pthread_rwlock_t *lock"
.Xc
Lock a read/write lock for writing, blocking until the lock can be
acquired.
.It Xo
.Ft int
.Fn pthread_rwlockattr_destroy "pthread_rwlockattr_t *attr"
.Xc
Destroy a read/write lock attribute object.
.It Xo
.Ft int
.Fo pthread_rwlockattr_getpshared
.Fa "const pthread_rwlockattr_t *attr" "int *pshared"
.Fc
.Xc
Retrieve the process shared setting for the read/write lock attribute
object.
.It Xo
.Ft int
.Fn pthread_rwlockattr_init "pthread_rwlockattr_t *attr"
.Xc
Initialize a read/write lock attribute object.
.It Xo
.Ft int
.Fn pthread_rwlockattr_setpshared "pthread_rwlockattr_t *attr" "int pshared"
.Xc
Set the process shared setting for the read/write lock attribute object.
.El
.Ss Per-Thread Context Routines
.Bl -tag -width indent
.It Xo
.Ft int
.Fn pthread_key_create "pthread_key_t *key" "void \*[lp]*routine\*[rp]\*[lp]void *\*[rp]"
.Xc
Create a thread-specific data key.
.It Xo
.Ft int
.Fn pthread_key_delete "pthread_key_t key"
.Xc
Delete a thread-specific data key.
.It Xo
.Ft "void *"
.Fn pthread_getspecific "pthread_key_t key"
.Xc
Get the thread-specific value for the specified key.
.It Xo
.Ft int
.Fn pthread_setspecific "pthread_key_t key" "const void *value_ptr"
.Xc
Set the thread-specific value for the specified key.
.El
.Ss Cleanup Routines
.Bl -tag -width indent
.It Xo
.Ft int
.Fo pthread_atfork
.Fa "void \*[lp]*prepare\*[rp]\*[lp]void\*[rp]"
.Fa "void \*[lp]*parent\*[rp]\*[lp]void\*[rp]"
.Fa "void \*[lp]*child\*[rp]\*[lp]void\*[rp]"
.Fc
.Xc
Register fork handlers
.It Xo
.Ft void
.Fn pthread_cleanup_pop "int execute"
.Xc
Remove the routine at the top of the calling thread's cancellation cleanup
stack and optionally invoke it.
.It Xo
.Ft void
.Fn pthread_cleanup_push "void \*[lp]*routine\*[rp]\*[lp]void *\*[rp]" "void *routine_arg"
.Xc
Push the specified cancellation cleanup handler onto the calling thread's
cancellation stack.
.El
.Sh INSTALLATION
The current
.Fx
POSIX thread implementation is built in two libraries,
.Lb libpthread ,
and
.Lb libthr .
They contain both thread-safe versions of
.Lb libc
functions and the thread functions.
Threaded applications are linked with one of these libraries.
.Sh SEE ALSO
.Xr pthread_atfork 3 ,
.Xr pthread_cleanup_pop 3 ,
.Xr pthread_cleanup_push 3 ,
.Xr pthread_condattr_destroy 3 ,
.Xr pthread_condattr_init 3 ,
.Xr pthread_cond_broadcast 3 ,
.Xr pthread_cond_destroy 3 ,
.Xr pthread_cond_init 3 ,
.Xr pthread_cond_signal 3 ,
.Xr pthread_cond_timedwait 3 ,
.Xr pthread_cond_wait 3 ,
.Xr pthread_create 3 ,
.Xr pthread_detach 3 ,
.Xr pthread_equal 3 ,
.Xr pthread_exit 3 ,
.Xr pthread_getspecific 3 ,
.Xr pthread_join 3 ,
.Xr pthread_key_delete 3 ,
.Xr pthread_kill 3 ,
.Xr pthread_mutexattr_destroy 3 ,
.Xr pthread_mutexattr_getprioceiling 3 ,
.Xr pthread_mutexattr_getprotocol 3 ,
.Xr pthread_mutexattr_gettype 3 ,
.Xr pthread_mutexattr_init 3 ,
.Xr pthread_mutexattr_setprioceiling 3 ,
.Xr pthread_mutexattr_setprotocol 3 ,
.Xr pthread_mutexattr_settype 3 ,
.Xr pthread_mutex_destroy 3 ,
.Xr pthread_mutex_init 3 ,
.Xr pthread_mutex_lock 3 ,
.Xr pthread_mutex_trylock 3 ,
.Xr pthread_mutex_unlock 3 ,
.Xr pthread_once 3 ,
.Xr pthread_rwlockattr_destroy 3 ,
.Xr pthread_rwlockattr_getpshared 3 ,
.Xr pthread_rwlockattr_init 3 ,
.Xr pthread_rwlockattr_setpshared 3 ,
.Xr pthread_rwlock_destroy 3 ,
.Xr pthread_rwlock_init 3 ,
.Xr pthread_rwlock_rdlock 3 ,
.Xr pthread_rwlock_unlock 3 ,
.Xr pthread_rwlock_wrlock 3 ,
.Xr pthread_self 3 ,
.Xr pthread_setcancelstate 3 ,
.Xr pthread_setcanceltype 3 ,
.Xr pthread_setspecific 3 ,
.Xr pthread_testcancel 3
.Sh STANDARDS
The functions with the
.Nm pthread_
prefix and not
.Nm _np
suffix or
.Nm pthread_rwlock
prefix conform to
.St -p1003.1-96 .
.Pp
The functions with the
.Nm pthread_
prefix and
.Nm _np
suffix are non-portable extensions to POSIX threads.
.Pp
The functions with the
.Nm pthread_rwlock
prefix are extensions created by The Open Group as part of the
.St -susv2 .