PTHREAD(3) BSD Library Functions Manual PTHREAD(3)NAME
pthread — POSIX thread functions
LIBRARY
POSIX Threads Library (libpthread, -lpthread)
SYNOPSIS
#include <pthread.h>
DESCRIPTION
POSIX threads are a set of functions that support applications with
requirements for multiple flows of control, called threads, within a
process. Multithreading is used to improve the performance of a program.
The POSIX thread functions are summarized in this section in the follow‐
ing groups:
· Thread Routines
· Attribute Object Routines
· Mutex Routines
· Condition Variable Routines
· Read/Write Lock Routines
· Per-Thread Context Routines
· Cleanup Routines
Thread Routines
int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
void *(*start_routine)(void *), void *arg)
Creates a new thread of execution.
int pthread_cancel(pthread_t thread)
Cancels execution of a thread.
int pthread_detach(pthread_t thread)
Marks a thread for deletion.
int pthread_equal(pthread_t t1, pthread_t t2)
Compares two thread IDs.
void pthread_exit(void *value_ptr)
Terminates the calling thread.
int pthread_join(pthread_t thread, void **value_ptr)
Causes the calling thread to wait for the termination of the
specified thread.
int pthread_kill(pthread_t thread, int sig)
Delivers a signal to a specified thread.
int pthread_once(pthread_once_t *once_control, void
(*init_routine)(void))
Calls an initialization routine once.
pthread_t pthread_self(void)
Returns the thread ID of the calling thread.
int pthread_setcancelstate(int state, int *oldstate)
Sets the current thread's cancelability state.
int pthread_setcanceltype(int type, int *oldtype)
Sets the current thread's cancelability type.
void pthread_testcancel(void)
Creates a cancellation point in the calling thread.
void pthread_yield(void)
Allows the scheduler to run another thread instead of the current
one.
Attribute Object Routines
int pthread_attr_destroy(pthread_attr_t *attr)
Destroy a thread attributes object.
int pthread_attr_getinheritsched(const pthread_attr_t *attr,
int *inheritsched)
Get the inherit scheduling attribute from a thread attributes
object.
int pthread_attr_getschedparam(const pthread_attr_t *attr,
struct sched_param *param)
Get the scheduling parameter attribute from a thread attributes
object.
int pthread_attr_getschedpolicy(const pthread_attr_t *attr, int *policy)
Get the scheduling policy attribute from a thread attributes
object.
int pthread_attr_getscope(const pthread_attr_t *attr, int
*contentionscope)
Get the contention scope attribute from a thread attributes
object.
int pthread_attr_getstacksize(const pthread_attr_t *attr, size_t
*stacksize)
Get the stack size attribute from a thread attributes object.
int pthread_attr_getstackaddr(const pthread_attr_t *attr, void
**stackaddr)
Get the stack address attribute from a thread attributes object.
int pthread_attr_getdetachstate(const pthread_attr_t *attr, int
*detachstate)
Get the detach state attribute from a thread attributes object.
int pthread_attr_init(pthread_attr_t *attr)
Initialize a thread attributes object with default values.
int pthread_attr_setinheritsched(pthread_attr_t *attr, int inheritsched)
Set the inherit scheduling attribute in a thread attributes
object.
int pthread_attr_setschedparam(pthread_attr_t *attr,
const struct sched_param *param)
Set the scheduling parameter attribute in a thread attributes
object.
int pthread_attr_setschedpolicy(pthread_attr_t *attr, int policy)
Set the scheduling policy attribute in a thread attributes
object.
int pthread_attr_setscope(pthread_attr_t *attr, int contentionscope)
Set the contention scope attribute in a thread attributes object.
int pthread_attr_setstacksize(pthread_attr_t *attr, size_t stacksize)
Set the stack size attribute in a thread attributes object.
int pthread_attr_setstackaddr(pthread_attr_t *attr, void *stackaddr)
Set the stack address attribute in a thread attributes object.
int pthread_attr_setdetachstate(pthread_attr_t *attr, int detachstate)
Set the detach state in a thread attributes object.
Mutex Routines
int pthread_mutexattr_destroy(pthread_mutexattr_t *attr)
Destroy a mutex attributes object.
int pthread_mutexattr_getprioceiling(pthread_mutexattr_t *attr, int
*ceiling)
Obtain priority ceiling attribute of mutex attribute object.
int pthread_mutexattr_getprotocol(pthread_mutexattr_t *attr, int
*protocol)
Obtain protocol attribute of mutex attribute object.
int pthread_mutexattr_gettype(pthread_mutexattr_t *attr, int *type)
Obtain the mutex type attribute in the specified mutex attributes
object.
int pthread_mutexattr_init(pthread_mutexattr_t *attr)
Initialize a mutex attributes object with default values.
int pthread_mutexattr_setprioceiling(pthread_mutexattr_t *attr, int
ceiling)
Set priority ceiling attribute of mutex attribute object.
int pthread_mutexattr_setprotocol(pthread_mutexattr_t *attr, int
protocol)
Set protocol attribute of mutex attribute object.
int pthread_mutexattr_settype(pthread_mutexattr_t *attr, int type)
Set the mutex type attribute that is used when a mutex is cre‐
ated.
int pthread_mutex_destroy(pthread_mutex_t *mutex)
Destroy a mutex.
int pthread_mutex_init(pthread_mutex_t *mutex,
const pthread_mutexattr_t *attr)
Initialize a mutex with specified attributes.
int pthread_mutex_lock(pthread_mutex_t *mutex)
Lock a mutex and block until it becomes available.
int pthread_mutex_timedlock(pthread_mutex_t *mutex,
const struct timespec *abstime)
Lock a mutex and block until it becomes available or until the
timeout expires.
int pthread_mutex_trylock(pthread_mutex_t *mutex)
Try to lock a mutex, but do not block if the mutex is locked by
another thread, including the current thread.
int pthread_mutex_unlock(pthread_mutex_t *mutex)
Unlock a mutex.
Condition Variable Routines
int pthread_condattr_destroy(pthread_condattr_t *attr)
Destroy a condition variable attributes object.
int pthread_condattr_init(pthread_condattr_t *attr)
Initialize a condition variable attributes object with default
values.
int pthread_cond_broadcast(pthread_cond_t *cond)
Unblock all threads currently blocked on the specified condition
variable.
int pthread_cond_destroy(pthread_cond_t *cond)
Destroy a condition variable.
int pthread_cond_init(pthread_cond_t *cond, const pthread_condattr_t
*attr)
Initialize a condition variable with specified attributes.
int pthread_cond_signal(pthread_cond_t *cond)
Unblock at least one of the threads blocked on the specified con‐
dition variable.
int 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.
int pthread_cond_wait(pthread_cond_t *, pthread_mutex_t *mutex)
Wait for a condition and lock the specified mutex.
Read/Write Lock Routines
int pthread_rwlock_destroy(pthread_rwlock_t *lock)
Destroy a read/write lock object.
int pthread_rwlock_init(pthread_rwlock_t *lock,
const pthread_rwlockattr_t *attr)
Initialize a read/write lock object.
int pthread_rwlock_rdlock(pthread_rwlock_t *lock)
Lock a read/write lock for reading, blocking until the lock can
be acquired.
int pthread_rwlock_tryrdlock(pthread_rwlock_t *lock)
Attempt to lock a read/write lock for reading, without blocking
if the lock is unavailable.
int pthread_rwlock_trywrlock(pthread_rwlock_t *lock)
Attempt to lock a read/write lock for writing, without blocking
if the lock is unavailable.
int pthread_rwlock_unlock(pthread_rwlock_t *lock)
Unlock a read/write lock.
int pthread_rwlock_wrlock(pthread_rwlock_t *lock)
Lock a read/write lock for writing, blocking until the lock can
be acquired.
int pthread_rwlockattr_destroy(pthread_rwlockattr_t *attr)
Destroy a read/write lock attribute object.
int pthread_rwlockattr_getpshared(const pthread_rwlockattr_t *attr,
int *pshared)
Retrieve the process shared setting for the read/write lock
attribute object.
int pthread_rwlockattr_init(pthread_rwlockattr_t *attr)
Initialize a read/write lock attribute object.
int pthread_rwlockattr_setpshared(pthread_rwlockattr_t *attr, int
pshared)
Set the process shared setting for the read/write lock attribute
object.
Per-Thread Context Routines
int pthread_key_create(pthread_key_t *key, void (*routine)(void *))
Create a thread-specific data key.
int pthread_key_delete(pthread_key_t key)
Delete a thread-specific data key.
void * pthread_getspecific(pthread_key_t key)
Get the thread-specific value for the specified key.
int pthread_setspecific(pthread_key_t key, const void *value_ptr)
Set the thread-specific value for the specified key.
Cleanup Routines
int pthread_atfork(void (*prepare)(void), void (*parent)(void),
void (*child)(void))
Register fork handlers
void pthread_cleanup_pop(int execute)
Remove the routine at the top of the calling thread's cancella‐
tion cleanup stack and optionally invoke it.
void pthread_cleanup_push(void (*routine)(void *), void *routine_arg)
Push the specified cancellation cleanup handler onto the calling
thread's cancellation stack.
IMPLEMENTATION NOTES
The current DragonFly POSIX thread implementation is built in the library
libthread_xu which contains both thread-safe libc functions and the
thread functions. Another thread library, libc_r, is available for test‐
ing purposes.
In DragonFly, it is possible to switch the threading library used by
dynamically linked binaries at execution time by re-linking
/usr/lib/libpthread.so.x to a different library in /usr/lib/thread. At
link time, ld(1) reads the SONAME of libpthread.so, which is set to
libpthread.so.0 (or a higher major, if there were ABI changes). For nor‐
mal libraries libfoo.so is usually a symlink to libfoo.so.3 which also
has its SONAME set to libfoo.so.3, so that if libfoo.so.4 is installed,
programs will still continue to use libfoo.so.3 and not follow the sym‐
link libfoo.so to the newer (and possibly incompatible) libfoo.so.4.
What we do for libpthread.so is approximately the opposite: libpthread.so
is not a symlink but nevertheless has its SONAME set to libpthread.so.0.
libpthread.so.0, however, is a symlink to the threading library of the
user's choice. The linker will use the default threading library which
libpthread.so is linked to, but the runtime linker will instead follow
the symlink.
libc.so defines all pthread functions as weak symbols except for
pthread_create() (which is defined by libpthread.so.x to satisfy ld(1)).
At execution time, rtld(1) will resolve all these references to the
strong symbols from the thread library.
By default, libc_r is built as part of a 'make buildworld'. To disable
the build of libc_r you must supply the '-DNO_LIBC_R' option to make(1)
(or set it in make.conf(5)).
Another make.conf(5) option, THREAD_LIB, can be used to override the sys‐
tem's default threading library.
A DragonFly specific option exists in gcc(1) to simplify the linking of
threaded processes. gcc -pthread links a threaded process against
libpthread.so instead of libc.
SEE ALSOpthread_atfork(3), pthread_cancel(3), pthread_cleanup_pop(3),
pthread_cleanup_push(3), pthread_condattr_destroy(3),
pthread_condattr_init(3), pthread_cond_broadcast(3),
pthread_cond_destroy(3), pthread_cond_init(3), pthread_cond_signal(3),
pthread_cond_timedwait(3), pthread_cond_wait(3), pthread_create(3),
pthread_detach(3), pthread_equal(3), pthread_exit(3),
pthread_getspecific(3), pthread_join(3), pthread_key_delete(3),
pthread_kill(3), pthread_mutexattr_destroy(3),
pthread_mutexattr_getprioceiling(3), pthread_mutexattr_getprotocol(3),
pthread_mutexattr_gettype(3), pthread_mutexattr_init(3),
pthread_mutexattr_setprioceiling(3), pthread_mutexattr_setprotocol(3),
pthread_mutexattr_settype(3), pthread_mutex_destroy(3),
pthread_mutex_init(3), pthread_mutex_lock(3), pthread_mutex_trylock(3),
pthread_mutex_unlock(3), pthread_once(3), pthread_rwlockattr_destroy(3),
pthread_rwlockattr_getpshared(3), pthread_rwlockattr_init(3),
pthread_rwlockattr_setpshared(3), pthread_rwlock_destroy(3),
pthread_rwlock_init(3), pthread_rwlock_rdlock(3),
pthread_rwlock_unlock(3), pthread_rwlock_wrlock(3), pthread_self(3),
pthread_setcancelstate(3), pthread_setcanceltype(3),
pthread_setspecific(3), pthread_testcancel(3)STANDARDS
The functions with the pthread_ prefix and not _np suffix or
pthread_rwlock prefix conform to ISO/IEC 9945-1:1996 (“POSIX.1”).
The functions with the pthread_ prefix and _np suffix are non-portable
extensions to POSIX threads.
The functions with the pthread_rwlock prefix are extensions created by
The Open Group as part of the Version 2 of the Single UNIX Specification
(“SUSv2”).
BSD April 8, 2010 BSD