From: Jakub Jelinek Date: Thu, 12 Jul 2007 18:26:36 +0000 (+0000) Subject: 2.5-18.1 X-Git-Tag: man-pages-6.06~226^2~2 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f7f73b1caae7ef3a9d58add8824ae2d77fc8d82f;p=thirdparty%2Fman-pages.git 2.5-18.1 --- diff --git a/linuxthreads/man/pthread_cond_init.man b/linuxthreads/man/pthread_cond_init.man deleted file mode 100644 index 4913062fd2..0000000000 --- a/linuxthreads/man/pthread_cond_init.man +++ /dev/null @@ -1,234 +0,0 @@ -.TH PTHREAD_COND 3 LinuxThreads - -.XREF pthread_cond_signal -.XREF pthread_cond_broadcast -.XREF pthread_cond_wait -.XREF pthread_cond_timedwait -.XREF pthread_cond_destroy - -.SH NAME -pthread_cond_init, pthread_cond_destroy, pthread_cond_signal, pthread_cond_broadcast, pthread_cond_wait, pthread_cond_timedwait \- operations on conditions - -.SH SYNOPSIS -#include - -pthread_cond_t cond = PTHREAD_COND_INITIALIZER; - -int pthread_cond_init(pthread_cond_t *cond, pthread_condattr_t *cond_attr); - -int pthread_cond_signal(pthread_cond_t *cond); - -int pthread_cond_broadcast(pthread_cond_t *cond); - -int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex); - -int pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex, const struct timespec *abstime); - -int pthread_cond_destroy(pthread_cond_t *cond); - -.SH DESCRIPTION - -A condition (short for ``condition variable'') is a synchronization -device that allows threads to suspend execution and relinquish the -processors until some predicate on shared data is satisfied. The basic -operations on conditions are: signal the condition (when the -predicate becomes true), and wait for the condition, suspending the -thread execution until another thread signals the condition. - -A condition variable must always be associated with a mutex, to avoid -the race condition where a thread prepares to wait on a condition -variable and another thread signals the condition just before the -first thread actually waits on it. - -!pthread_cond_init! initializes the condition variable |cond|, using the -condition attributes specified in |cond_attr|, or default attributes -if |cond_attr| is !NULL!. The LinuxThreads implementation supports no -attributes for conditions, hence the |cond_attr| parameter is actually -ignored. - -Variables of type !pthread_cond_t! can also be initialized -statically, using the constant !PTHREAD_COND_INITIALIZER!. - -!pthread_cond_signal! restarts one of the threads that are waiting on -the condition variable |cond|. If no threads are waiting on |cond|, -nothing happens. If several threads are waiting on |cond|, exactly one -is restarted, but it is not specified which. - -!pthread_cond_broadcast! restarts all the threads that are waiting on -the condition variable |cond|. Nothing happens if no threads are -waiting on |cond|. - -!pthread_cond_wait! atomically unlocks the |mutex| (as per -!pthread_unlock_mutex!) and waits for the condition variable |cond| to -be signaled. The thread execution is suspended and does not consume -any CPU time until the condition variable is signaled. The |mutex| -must be locked by the calling thread on entrance to -!pthread_cond_wait!. Before returning to the calling thread, -!pthread_cond_wait! re-acquires |mutex| (as per !pthread_lock_mutex!). - -Unlocking the mutex and suspending on the condition variable is done -atomically. Thus, if all threads always acquire the mutex before -signaling the condition, this guarantees that the condition cannot be -signaled (and thus ignored) between the time a thread locks the mutex -and the time it waits on the condition variable. - -!pthread_cond_timedwait! atomically unlocks |mutex| and waits on -|cond|, as !pthread_cond_wait! does, but it also bounds the duration -of the wait. If |cond| has not been signaled within the amount of time -specified by |abstime|, the mutex |mutex| is re-acquired and -!pthread_cond_timedwait! returns the error !ETIMEDOUT!. -The |abstime| parameter specifies an absolute time, with the same -origin as !time!(2) and !gettimeofday!(2): an |abstime| of 0 -corresponds to 00:00:00 GMT, January 1, 1970. - -!pthread_cond_destroy! destroys a condition variable, freeing the -resources it might hold. No threads must be waiting on the condition -variable on entrance to !pthread_cond_destroy!. In the LinuxThreads -implementation, no resources are associated with condition variables, -thus !pthread_cond_destroy! actually does nothing except checking that -the condition has no waiting threads. - -.SH CANCELLATION - -!pthread_cond_wait! and !pthread_cond_timedwait! are cancellation -points. If a thread is cancelled while suspended in one of these -functions, the thread immediately resumes execution, then locks again -the |mutex| argument to !pthread_cond_wait! and -!pthread_cond_timedwait!, and finally executes the cancellation. -Consequently, cleanup handlers are assured that |mutex| is locked when -they are called. - -.SH "ASYNC-SIGNAL SAFETY" - -The condition functions are not async-signal safe, and should not be -called from a signal handler. In particular, calling -!pthread_cond_signal! or !pthread_cond_broadcast! from a signal -handler may deadlock the calling thread. - -.SH "RETURN VALUE" - -All condition variable functions return 0 on success and a non-zero -error code on error. - -.SH ERRORS - -!pthread_cond_init!, !pthread_cond_signal!, !pthread_cond_broadcast!, -and !pthread_cond_wait! never return an error code. - -The !pthread_cond_timedwait! function returns the following error codes -on error: -.RS -.TP -!ETIMEDOUT! -the condition variable was not signaled until the timeout specified by -|abstime| - -.TP -!EINTR! -!pthread_cond_timedwait! was interrupted by a signal -.RE - -The !pthread_cond_destroy! function returns the following error code -on error: -.RS -.TP -!EBUSY! -some threads are currently waiting on |cond|. -.RE - -.SH AUTHOR -Xavier Leroy - -.SH "SEE ALSO" -!pthread_condattr_init!(3), -!pthread_mutex_lock!(3), -!pthread_mutex_unlock!(3), -!gettimeofday!(2), -!nanosleep!(2). - -.SH EXAMPLE - -Consider two shared variables |x| and |y|, protected by the mutex |mut|, -and a condition variable |cond| that is to be signaled whenever |x| -becomes greater than |y|. - -.RS -.ft 3 -.nf -.sp -int x,y; -pthread_mutex_t mut = PTHREAD_MUTEX_INITIALIZER; -pthread_cond_t cond = PTHREAD_COND_INITIALIZER; -.ft -.LP -.RE -.fi - -Waiting until |x| is greater than |y| is performed as follows: - -.RS -.ft 3 -.nf -.sp -pthread_mutex_lock(&mut); -while (x <= y) { - pthread_cond_wait(&cond, &mut); -} -/* operate on x and y */ -pthread_mutex_unlock(&mut); -.ft -.LP -.RE -.fi - -Modifications on |x| and |y| that may cause |x| to become greater than -|y| should signal the condition if needed: - -.RS -.ft 3 -.nf -.sp -pthread_mutex_lock(&mut); -/* modify x and y */ -if (x > y) pthread_cond_broadcast(&cond); -pthread_mutex_unlock(&mut); -.ft -.LP -.RE -.fi - -If it can be proved that at most one waiting thread needs to be waken -up (for instance, if there are only two threads communicating through -|x| and |y|), !pthread_cond_signal! can be used as a slightly more -efficient alternative to !pthread_cond_broadcast!. In doubt, use -!pthread_cond_broadcast!. - -To wait for |x| to becomes greater than |y| with a timeout of 5 -seconds, do: - -.RS -.ft 3 -.nf -.sp -struct timeval now; -struct timespec timeout; -int retcode; - -pthread_mutex_lock(&mut); -gettimeofday(&now); -timeout.tv_sec = now.tv_sec + 5; -timeout.tv_nsec = now.tv_usec * 1000; -retcode = 0; -while (x <= y && retcode != ETIMEDOUT) { - retcode = pthread_cond_timedwait(&cond, &mut, &timeout); -} -if (retcode == ETIMEDOUT) { - /* timeout occurred */ -} else { - /* operate on x and y */ -} -pthread_mutex_unlock(&mut); -.ft -.LP -.RE -.fi diff --git a/linuxthreads/man/pthread_condattr_init.man b/linuxthreads/man/pthread_condattr_init.man deleted file mode 100644 index f491cbedbe..0000000000 --- a/linuxthreads/man/pthread_condattr_init.man +++ /dev/null @@ -1,39 +0,0 @@ -.TH PTHREAD_CONDATTR 3 LinuxThreads - -.XREF pthread_condattr_destroy - -.SH NAME -pthread_condattr_init, pthread_condattr_destroy \- condition creation attributes - -.SH SYNOPSIS -#include - -int pthread_condattr_init(pthread_condattr_t *attr); - -int pthread_condattr_destroy(pthread_condattr_t *attr); - -.SH DESCRIPTION - -Condition attributes can be specified at condition creation time, by passing a -condition attribute object as second argument to !pthread_cond_init!(3). -Passing !NULL! is equivalent to passing a condition attribute object with -all attributes set to their default values. - -The LinuxThreads implementation supports no attributes for -conditions. The functions on condition attributes are included only -for compliance with the POSIX standard. - -!pthread_condattr_init! initializes the condition attribute object -|attr| and fills it with default values for the attributes. -!pthread_condattr_destroy! destroys a condition attribute object, -which must not be reused until it is reinitialized. Both functions do -nothing in the LinuxThreads implementation. - -.SH "RETURN VALUE" -!pthread_condattr_init! and !pthread_condattr_destroy! always return 0. - -.SH AUTHOR -Xavier Leroy - -.SH "SEE ALSO" -!pthread_cond_init!(3). diff --git a/linuxthreads/man/pthread_key_create.man b/linuxthreads/man/pthread_key_create.man deleted file mode 100644 index 6823e304c9..0000000000 --- a/linuxthreads/man/pthread_key_create.man +++ /dev/null @@ -1,151 +0,0 @@ -.TH PTHREAD_SPECIFIC 3 LinuxThreads - -.SH NAME -pthread_key_create, pthread_key_delete, pthread_setspecific, pthread_getspecific \- management of thread-specific data - -.SH SYNOPSIS -#include - -int pthread_key_create(pthread_key_t *key, void (*destr_function) (void *)); - -int pthread_key_delete(pthread_key_t key); - -int pthread_setspecific(pthread_key_t key, const void *pointer); - -void * pthread_getspecific(pthread_key_t key); - -.SH DESCRIPTION - -Programs often need global or static variables that have different -values in different threads. Since threads share one memory space, -this cannot be achieved with regular variables. Thread-specific data -is the POSIX threads answer to this need. - -Each thread possesses a private memory block, the thread-specific data -area, or TSD area for short. This area is indexed by TSD keys. The TSD -area associates values of type !void *! to TSD keys. TSD keys are -common to all threads, but the value associated with a given TSD key -can be different in each thread. - -For concreteness, the TSD areas can be viewed as arrays of !void *! -pointers, TSD keys as integer indices into these arrays, and the value -of a TSD key as the value of the corresponding array element in the -calling thread. - -When a thread is created, its TSD area initially associates !NULL! -with all keys. - -!pthread_key_create! allocates a new TSD key. The key is stored in the -location pointed to by |key|. There is a limit of !PTHREAD_KEYS_MAX! -on the number of keys allocated at a given time. The value initially -associated with the returned key is !NULL! in all currently executing -threads. - -The |destr_function| argument, if not !NULL!, specifies a destructor -function associated with the key. When a thread terminates via -!pthread_exit! or by cancellation, |destr_function| is called with -arguments the value associated with the key in that thread. The -|destr_function| is not called if that value is !NULL!. The order in -which destructor functions are called at thread termination time is -unspecified. - -Before the destructor function is called, the !NULL! value is -associated with the key in the current thread. A destructor function -might, however, re-associate non-!NULL! values to that key or some -other key. To deal with this, if after all the destructors have been -called for all non-!NULL! values, there are still some non-!NULL! -values with associated destructors, then the process is repeated. The -LinuxThreads implementation stops the process after -!PTHREAD_DESTRUCTOR_ITERATIONS! iterations, even if some non-!NULL! -values with associated descriptors remain. Other implementations may -loop indefinitely. - -!pthread_key_delete! deallocates a TSD key. It does not check whether -non-!NULL! values are associated with that key in the currently -executing threads, nor call the destructor function associated with -the key. - -!pthread_setspecific! changes the value associated with |key| in the -calling thread, storing the given |pointer| instead. - -!pthread_getspecific! returns the value currently associated with -|key| in the calling thread. - -.SH "RETURN VALUE" - -!pthread_key_create!, !pthread_key_delete!, and !pthread_setspecific! -return 0 on success and a non-zero error code on failure. If -successful, !pthread_key_create! stores the newly allocated key in the -location pointed to by its |key| argument. - -!pthread_getspecific! returns the value associated with |key| on -success, and !NULL! on error. - -.SH ERRORS -!pthread_key_create! returns the following error code on error: -.RS -.TP -!EAGAIN! -!PTHREAD_KEYS_MAX! keys are already allocated -.RE - -!pthread_key_delete! and !pthread_setspecific! return the following -error code on error: -.RS -.TP -!EINVAL! -|key| is not a valid, allocated TSD key -.RE - -!pthread_getspecific! returns !NULL! if |key| is not a valid, -allocated TSD key. - -.SH AUTHOR -Xavier Leroy - -.SH "SEE ALSO" -pthread_create(3), pthread_exit(3), pthread_testcancel(3). - -.SH EXAMPLE - -The following code fragment allocates a thread-specific array of 100 -characters, with automatic reclaimation at thread exit: - -.RS -.ft 3 -.nf -.sp -/* Key for the thread-specific buffer */ -static pthread_key_t buffer_key; - -/* Once-only initialisation of the key */ -static pthread_once_t buffer_key_once = PTHREAD_ONCE_INIT; - -/* Allocate the thread-specific buffer */ -void buffer_alloc(void) -{ - pthread_once(&buffer_key_once, buffer_key_alloc); - pthread_setspecific(buffer_key, malloc(100)); -} - -/* Return the thread-specific buffer */ -char * get_buffer(void) -{ - return (char *) pthread_getspecific(buffer_key); -} - -/* Allocate the key */ -static void buffer_key_alloc() -{ - pthread_key_create(&buffer_key, buffer_destroy); -} - -/* Free the thread-specific buffer */ -static void buffer_destroy(void * buf) -{ - free(buf); -} -.ft -.LP -.RE -.fi diff --git a/linuxthreads/man/pthread_mutex_init.man b/linuxthreads/man/pthread_mutex_init.man deleted file mode 100644 index 643b007aec..0000000000 --- a/linuxthreads/man/pthread_mutex_init.man +++ /dev/null @@ -1,213 +0,0 @@ -.TH PTHREAD_MUTEX 3 LinuxThreads - -.XREF pthread_mutex_lock -.XREF pthread_mutex_unlock -.XREF pthread_mutex_trylock -.XREF pthread_mutex_destroy - -.SH NAME -pthread_mutex_init, pthread_mutex_lock, pthread_mutex_trylock, pthread_mutex_unlock, pthread_mutex_destroy \- operations on mutexes - -.SH SYNOPSIS -#include - -pthread_mutex_t fastmutex = PTHREAD_MUTEX_INITIALIZER; - -pthread_mutex_t recmutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP; - -pthread_mutex_t errchkmutex = PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP; - -int pthread_mutex_init(pthread_mutex_t *mutex, const pthread_mutexattr_t *mutexattr); - -int pthread_mutex_lock(pthread_mutex_t *mutex); - -int pthread_mutex_trylock(pthread_mutex_t *mutex); - -int pthread_mutex_unlock(pthread_mutex_t *mutex); - -int pthread_mutex_destroy(pthread_mutex_t *mutex); - -.SH DESCRIPTION -A mutex is a MUTual EXclusion device, and is useful for protecting -shared data structures from concurrent modifications, and implementing -critical sections and monitors. - -A mutex has two possible states: unlocked (not owned by any thread), -and locked (owned by one thread). A mutex can never be owned by two -different threads simultaneously. A thread attempting to lock a mutex -that is already locked by another thread is suspended until the owning -thread unlocks the mutex first. - -!pthread_mutex_init! initializes the mutex object pointed to by -|mutex| according to the mutex attributes specified in |mutexattr|. -If |mutexattr| is !NULL!, default attributes are used instead. - -The LinuxThreads implementation supports only one mutex attributes, -the |mutex kind|, which is either ``fast'', ``recursive'', or -``error checking''. The kind of a mutex determines whether -it can be locked again by a thread that already owns it. -The default kind is ``fast''. See !pthread_mutexattr_init!(3) for more -information on mutex attributes. - -Variables of type !pthread_mutex_t! can also be initialized -statically, using the constants !PTHREAD_MUTEX_INITIALIZER! (for fast -mutexes), !PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP! (for recursive -mutexes), and !PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP! (for error checking -mutexes). - -!pthread_mutex_lock! locks the given mutex. If the mutex is currently -unlocked, it becomes locked and owned by the calling thread, and -!pthread_mutex_lock! returns immediately. If the mutex is already -locked by another thread, !pthread_mutex_lock! suspends the calling -thread until the mutex is unlocked. - -If the mutex is already locked by the calling thread, the behavior of -!pthread_mutex_lock! depends on the kind of the mutex. If the mutex is -of the ``fast'' kind, the calling thread is suspended until the mutex -is unlocked, thus effectively causing the calling thread to -deadlock. If the mutex is of the ``error checking'' kind, -!pthread_mutex_lock! returns immediately with the error code !EDEADLK!. -If the mutex is of the ``recursive'' kind, !pthread_mutex_lock! -succeeds and returns immediately, recording the number of times the -calling thread has locked the mutex. An equal number of -!pthread_mutex_unlock! operations must be performed before the mutex -returns to the unlocked state. - -!pthread_mutex_trylock! behaves identically to !pthread_mutex_lock!, -except that it does not block the calling thread if the mutex is -already locked by another thread (or by the calling thread in the case -of a ``fast'' mutex). Instead, !pthread_mutex_trylock! returns -immediately with the error code !EBUSY!. - -!pthread_mutex_unlock! unlocks the given mutex. The mutex is assumed -to be locked and owned by the calling thread on entrance to -!pthread_mutex_unlock!. If the mutex is of the ``fast'' kind, -!pthread_mutex_unlock! always returns it to the unlocked state. If it -is of the ``recursive'' kind, it decrements the locking count of the -mutex (number of !pthread_mutex_lock! operations performed on it by -the calling thread), and only when this count reaches zero is the -mutex actually unlocked. - -On ``error checking'' mutexes, !pthread_mutex_unlock! actually checks -at run-time that the mutex is locked on entrance, and that it was -locked by the same thread that is now calling !pthread_mutex_unlock!. -If these conditions are not met, an error code is returned and the -mutex remains unchanged. ``Fast'' and ``recursive'' mutexes perform -no such checks, thus allowing a locked mutex to be unlocked by a -thread other than its owner. This is non-portable behavior and must -not be relied upon. - -!pthread_mutex_destroy! destroys a mutex object, freeing the resources -it might hold. The mutex must be unlocked on entrance. In the -LinuxThreads implementation, no resources are associated with mutex -objects, thus !pthread_mutex_destroy! actually does nothing except -checking that the mutex is unlocked. - -.SH CANCELLATION - -None of the mutex functions is a cancellation point, not even -!pthread_mutex_lock!, in spite of the fact that it can suspend a -thread for arbitrary durations. This way, the status of mutexes at -cancellation points is predictable, allowing cancellation handlers to -unlock precisely those mutexes that need to be unlocked before the -thread stops executing. Consequently, threads using deferred -cancellation should never hold a mutex for extended periods of time. - -.SH "ASYNC-SIGNAL SAFETY" - -The mutex functions are not async-signal safe. What this means is that -they should not be called from a signal handler. In particular, -calling !pthread_mutex_lock! or !pthread_mutex_unlock! from a signal -handler may deadlock the calling thread. - -.SH "RETURN VALUE" - -!pthread_mutex_init! always returns 0. The other mutex functions -return 0 on success and a non-zero error code on error. - -.SH ERRORS - -The !pthread_mutex_lock! function returns the following error code -on error: -.RS -.TP -!EINVAL! -the mutex has not been properly initialized. - -.TP -!EDEADLK! -the mutex is already locked by the calling thread -(``error checking'' mutexes only). -.RE - -The !pthread_mutex_trylock! function returns the following error codes -on error: -.RS -.TP -!EBUSY! -the mutex could not be acquired because it was currently locked. - -.TP -!EINVAL! -the mutex has not been properly initialized. -.RE - -The !pthread_mutex_unlock! function returns the following error code -on error: -.RS -.TP -!EINVAL! -the mutex has not been properly initialized. - -.TP -!EPERM! -the calling thread does not own the mutex (``error checking'' mutexes only). -.RE - -The !pthread_mutex_destroy! function returns the following error code -on error: -.RS -.TP -!EBUSY! -the mutex is currently locked. -.RE - -.SH AUTHOR -Xavier Leroy - -.SH "SEE ALSO" -!pthread_mutexattr_init!(3), -!pthread_mutexattr_setkind_np!(3), -!pthread_cancel!(3). - -.SH EXAMPLE - -A shared global variable |x| can be protected by a mutex as follows: - -.RS -.ft 3 -.nf -.sp -int x; -pthread_mutex_t mut = PTHREAD_MUTEX_INITIALIZER; -.ft -.LP -.RE -.fi - -All accesses and modifications to |x| should be bracketed by calls to -!pthread_mutex_lock! and !pthread_mutex_unlock! as follows: - -.RS -.ft 3 -.nf -.sp -pthread_mutex_lock(&mut); -/* operate on x */ -pthread_mutex_unlock(&mut); -.ft -.LP -.RE -.fi - - diff --git a/linuxthreads/man/pthread_mutexattr_setkind_np.man b/linuxthreads/man/pthread_mutexattr_setkind_np.man deleted file mode 100644 index e10f47d0e5..0000000000 --- a/linuxthreads/man/pthread_mutexattr_setkind_np.man +++ /dev/null @@ -1,39 +0,0 @@ -.TH PTHREAD_MUTEXATTR_SETKIND_NP 3 LinuxThreads - -.XREF pthread_mutexattr_getkind_np - -.SH NAME -pthread_mutexattr_setkind_np, pthread_mutexattr_getkind_np \- deprecated mutex creation attributes - -.SH SYNOPSIS -#include - -int pthread_mutexattr_setkind_np(pthread_mutexattr_t *attr, int kind); - -int pthread_mutexattr_getkind_np(const pthread_mutexattr_t *attr, int *kind); - -.SH DESCRIPTION - -These functions are deprecated, use !pthread_mutexattr_settype!(3) -and !pthread_mutexattr_gettype!(3) instead. - -.SH "RETURN VALUE" -!pthread_mutexattr_getkind_np! always returns 0. - -!pthread_mutexattr_setkind_np! returns 0 on success and a non-zero -error code on error. - -.SH ERRORS - -On error, !pthread_mutexattr_setkind_np! returns the following error code: -.TP -!EINVAL! -|kind| is neither !PTHREAD_MUTEX_FAST_NP! nor !PTHREAD_MUTEX_RECURSIVE_NP! -nor !PTHREAD_MUTEX_ERRORCHECK_NP! - -.SH AUTHOR -Xavier Leroy - -.SH "SEE ALSO" -!pthread_mutexattr_settype!(3), -!pthread_mutexattr_gettype!(3). diff --git a/linuxthreads/man/pthread_once.man b/linuxthreads/man/pthread_once.man deleted file mode 100644 index e9d117b656..0000000000 --- a/linuxthreads/man/pthread_once.man +++ /dev/null @@ -1,34 +0,0 @@ -.TH PTHREAD_ONCE 3 LinuxThreads - -.SH NAME -pthread_once \- once-only initialization - -.SH SYNOPSIS -#include - -pthread_once_t once_control = PTHREAD_ONCE_INIT; - -int pthread_once(pthread_once_t *once_control, void (*init_routine) (void)); - -.SH DESCRIPTION - -The purpose of !pthread_once! is to ensure that a piece of -initialization code is executed at most once. The |once_control| -argument points to a static or extern variable statically initialized -to !PTHREAD_ONCE_INIT!. - -The first time !pthread_once! is called with a given |once_control| -argument, it calls |init_routine| with no argument and changes the -value of the |once_control| variable to record that initialization has -been performed. Subsequent calls to !pthread_once! with the same -!once_control! argument do nothing. - -.SH "RETURN VALUE" -!pthread_once! always returns 0. - -.SH ERRORS -None. - -.SH AUTHOR -Xavier Leroy -