.\" Copyright (c) 1996 John Birrell <jb@cimlogic.com.au>.
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.\"	$Id: pthread.3,v 1.6 1998/04/10 09:33:09 jb Exp $
.\"
.Dd September 10, 1998
.Dt PTHREAD 3
.Os BSD 4
.Sh NAME
.Nm pthread
.Nd POSIX thread functions
.Sh DESCRIPTION
POSIX threads are a set of functions that support applications with
requirements for multiple flows of control, called
.Fa 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:
.Bl -bullet -offset indent
.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
.Sh THREAD ROUTINES
.Bl -tag -width Er
.It int Fn pthread_create "pthread_t *thread" "const pthread_attr_t *attr" "void *(*start_routine)(void *)" "void *arg"
Creates a new thread of execution.
.It int Fn pthread_detach "pthread_t thread"
Marks a thread for deletion.
.It int Fn pthread_equal "pthread_t t1" "pthread_t t2"
Compares two thread IDs.
.It void Fn pthread_exit "void *value_ptr"
Terminates the calling thread.
.It int Fn pthread_join "pthread_t thread" "void **value_ptr"
Causes the calling thread to wait for the termination of the specified thread.
.It int Fn pthread_once "pthread_once_t *once_control" "void (*init_routine)(void)"
Calls an initialization routine once.
.It pthread_t Fn pthread_self void
Returns the thread ID of the calling thread.
.El
.Sh ATTRIBUTE OBJECT ROUTINES
.Bl -tag -width Er
.It int Fn pthread_attr_destroy "pthread_attr_t *attr"
Destroy a thread attributes object.
.It int Fn pthread_attr_getinheritsched "pthread_attr_t *attr" "int *inheritsched"
Get the inherit scheduling attribute from a thread attributes object.
.It int Fn pthread_attr_getschedparam "pthread_attr_t *attr" "struct sched_param *param"
Get the scheduling parameter attribute from a thread attributes object.
.It int Fn pthread_attr_getschedpolicy "pthread_attr_t *attr" "int *policy"
Get the scheduling policy attribute from a thread attributes object.
.It int Fn pthread_attr_getscope "pthread_attr_t *attr" "int *contentionscope"
Get the contention scope attribute from a thread attributes object.
.It int Fn pthread_attr_getstacksize "pthread_attr_t *attr" "size_t *stacksize"
Get the stack size attribute from a thread attributes object.
.It int Fn pthread_attr_getstackaddr "pthread_attr_t *attr" "void **stackaddr"
Get the stack address attribute from a thread attributes object.
.It int Fn pthread_attr_getdetachstate "pthread_attr_t *attr" "int *detachstate"
Get the detach state attribute from a thread attributes object.
.It int Fn pthread_attr_init "pthread_attr_t *attr"
Initialize a thread attributes object with default values.
.It int Fn pthread_attr_setinheritsched "pthread_attr_t *attr" "int inheritsched"
Set the inherit scheduling attribute in a thread attributes object.
.It int Fn pthread_attr_setschedparam "pthread_attr_t *attr" "struct sched_param *param"
Set the scheduling parameter attribute in a thread attributes object.
.It int Fn pthread_attr_setschedpolicy "pthread_attr_t *attr" "int policy"
Set the scheduling policy attribute in a thread attributes object.
.It int Fn pthread_attr_setscope "pthread_attr_t *attr" "int contentionscope"
Set the contention scope attribute in a thread attributes object.
.It int Fn pthread_attr_setstacksize "pthread_attr_t *attr" "size_t stacksize"
Set the stack size attribute in a thread attributes object.
.It int Fn pthread_attr_setstackaddr "pthread_attr_t *attr" "void *stackaddr"
Set the stack address attribute in a thread attributes object.
.It int Fn pthread_attr_setdetachstate "pthread_attr_t *attr" "int detachstate"
Set the detach state in a thread attributes object.
.El
.Sh MUTEX ROUTINES
.Bl -tag -width Er
.It int Fn pthread_mutexattr_destroy "pthread_mutexattr_t *attr"
Destroy a mutex attributes object.
.It int Fn pthread_mutexattr_init "pthread_mutexattr_t *attr"
Initialize a mutex attributes object with default values.
.It int Fn pthread_mutex_destroy "pthread_mutex_t *mutex"
Destroy a mutex.
.It int Fn pthread_mutex_init "pthread_mutex_t *mutex" "const pthread_mutexattr_t *attr"
Initialize a mutex with specified attributes.
.It int Fn pthread_mutex_lock "pthread_mutex_t *mutex"
Lock a mutex and block until it becomes available.
.It int Fn pthread_mutex_trylock "pthread_mutex_t *mutex"
Try to lock a mutex, but don't block if the mutex is locked by another thread,
including the current thread.
.It int Fn pthread_mutex_unlock "pthread_mutex_t *mutex"
Unlock a mutex.
.El
.Sh CONDITION VARIABLE ROUTINES
.Bl -tag -width Er
.It int Fn pthread_condattr_init "pthread_condattr_t *attr"
Initialize a condition variable attributes object with default values.
.It int Fn pthread_condattr_destroy "pthread_condattr_t *attr"
Destroy a condition variable attributes object.
.It int Fn pthread_cond_broadcast "pthread_cond_t *cond"
Unblock all threads currently blocked on the specified condition variable.
.It int Fn pthread_cond_destroy "pthread_cond_t *cond"
Destroy a condition variable.
.It int Fn pthread_cond_init "pthread_cond_t *cond" "const pthread_condattr_t *attr"
Initialize a condition variable with specified attributes.
.It int Fn pthread_cond_signal "pthread_cond_t *cond"
Unblock at least one of the threads blocked on the specified condition variable.
.It int Fn pthread_cond_timedwait "pthread_cond_t *cond" "pthread_mutex_t *mutex" "const struct timespec *abstime"
Wait no longer than the specified time for a condition and lock the specified mutex.
.It int Fn pthread_cond_wait "pthread_cond_t *" "pthread_mutex_t *mutex"
Wait for a condition and lock the specified mutex.
.El
.Sh READ/WRITE LOCK ROUTINES
.Bl -tag -width Er
.It int Fn pthread_rwlock_destroy "pthread_rwlock_t *lock"
Destroy a read/write lock object.
.It int Fn pthread_rwlock_init "pthread_rwlock_t *lock" "const pthread_rwlockattr_t *attr"
Initialize a read/write lock object.
.It int Fn pthread_rwlock_rdlock "pthread_rwlock_t *lock"
Lock a read/write lock for reading, blocking until the lock can be
acquired.
.It int Fn pthread_rwlock_tryrdlock "pthread_rwlock_t *lock"
Attempt to lock a read/write lock for reading, without blocking if the
lock is unavailable.
.It int Fn pthread_rwlock_trywrlock "pthread_rwlock_t *lock"
Attempt to lock a read/write lock for writing, without blocking if the
lock is unavailable.
.It int Fn pthread_rwlock_unlock "pthread_rwlock_t *lock"
Unlock a read/write lock.
.It int Fn pthread_rwlock_wrlock "pthread_rwlock_t *lock"
Lock a read/write lock for writing, blocking until the lock can be
acquired.
.It int Fn pthread_rwlockattr_destroy "pthread_rwlockattr_t *attr"
Destroy a read/write lock attribute object.
.It int Fn pthread_rwlockattr_getpshared "pthread_rwlockattr_t *attr" "int *pshared"
Retrieve the process shared setting for the read/write lock attribute
object.
.It int Fn pthread_rwlockattr_init "pthread_rwlockattr_t *attr"
Initialize a read/write lock attribute object.
.It int Fn pthread_rwlockattr_setpshared "pthread_rwlockattr_t *attr" "int *pshared"
Set the process shared setting for the read/write lock attribute object.
.El
.Sh PER-THREAD CONTEXT ROUTINES
.Bl -tag -width Er
.It int Fn pthread_key_create "pthread_key_t *key" "void (*routine)(void *)"
Create a thread-specific data key.
.It int Fn pthread_key_delete "pthread_key_t key"
Delete a thread-specific data key.
.It void * Fn pthread_getspecific "pthread_key_t key" "void **value_ptr"
Get the thread-specific value for the specified key.
.It int Fn pthread_setspecific "pthread_key_t key" "const void *value_ptr"
Set the thread-specific value for the specified key.
.El
.Sh CLEANUP ROUTINES
.Bl -tag -width Er
.It void Fn pthread_cleanup_pop "int execute"
Remove the routine at the top of the calling thread's cancellation cleanup
stack and optionally invoke it.
.It void Fn pthread_cleanup_push "void (*routine)(void *)" "void *routine_arg"
Push the specified cancellation cleanup handler onto the calling thread's 
cancellation stack.
.El
.Sh INSTALLATION
The current FreeBSD POSIX thread implementation is built in the library
.Fa libc_r
which contains both thread-safe libc functions and the thread functions.
This library replaces
.Fa libc
for threaded applications.
.Pp
By default,
.Fa libc_r
is built as part of a 'make world'.  To disable the build of
.Fa libc_r
you must supply the '-DNOLIBC_R' option to
.Xr make 1 .
.Pp
A FreeBSD specific option has been added to gcc to make linking
threaded processes simple.
.Fa gcc -pthread
links a threaded process against
.Fa libc_r
instead of
.Fa libc.
.Sh STANDARDS
The functions in
.Fa libc_r
with the
.Fa pthread_
prefix and not
.Fa _np
suffix or
.Fa pthread_rwlock
prefix conform to IEEE
.Pq Dq Tn POSIX
Std 1003.1 Second Edition 1996-07-12
.Pp
The functions in libc_r with the
.Fa pthread_
prefix and
.Fa _np
suffix are non-portable extensions to POSIX threads.
.Pp
The functions in libc_r with the
.Fa pthread_rwlock
prefix are extensions created by The Open Group as part of the Single
UNIX Specification, Version 2.