NAME
pthread_exit - thread termination
SYNOPSIS
#include <pthread.h>
void pthread_exit(void *value_ptr);
DESCRIPTION
The pthread_exit() function shall terminate the calling thread and make
the value value_ptr available to any successful join with the
terminating thread. Any cancellation cleanup handlers that have been
pushed and not yet popped shall be popped in the reverse order that
they were pushed and then executed. After all cancellation cleanup
handlers have been executed, if the thread has any thread-specific
data, appropriate destructor functions shall be called in an
unspecified order. Thread termination does not release any application
visible process resources, including, but not limited to, mutexes and
file descriptors, nor does it perform any process-level cleanup
actions, including, but not limited to, calling any atexit() routines
that may exist.
An implicit call to pthread_exit() is made when a thread other than the
thread in which main() was first invoked returns from the start routine
that was used to create it. The function’s return value shall serve as
the thread’s exit status.
The behavior of pthread_exit() is undefined if called from a
cancellation cleanup handler or destructor function that was invoked as
a result of either an implicit or explicit call to pthread_exit().
After a thread has terminated, the result of access to local (auto)
variables of the thread is undefined. Thus, references to local
variables of the exiting thread should not be used for the
pthread_exit() value_ptr parameter value.
The process shall exit with an exit status of 0 after the last thread
has been terminated. The behavior shall be as if the implementation
called exit() with a zero argument at thread termination time.
RETURN VALUE
The pthread_exit() function cannot return to its caller.
ERRORS
No errors are defined.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
None.
RATIONALE
The normal mechanism by which a thread terminates is to return from the
routine that was specified in the pthread_create() call that started
it. The pthread_exit() function provides the capability for a thread to
terminate without requiring a return from the start routine of that
thread, thereby providing a function analogous to exit().
Regardless of the method of thread termination, any cancellation
cleanup handlers that have been pushed and not yet popped are executed,
and the destructors for any existing thread-specific data are executed.
This volume of IEEE Std 1003.1-2001 requires that cancellation cleanup
handlers be popped and called in order. After all cancellation cleanup
handlers have been executed, thread-specific data destructors are
called, in an unspecified order, for each item of thread-specific data
that exists in the thread. This ordering is necessary because
cancellation cleanup handlers may rely on thread-specific data.
As the meaning of the status is determined by the application (except
when the thread has been canceled, in which case it is
PTHREAD_CANCELED), the implementation has no idea what an illegal
status value is, which is why no address error checking is done.
FUTURE DIRECTIONS
None.
SEE ALSO
_exit(2), exit(3), pthread_create(3), pthread_join(3), the Base
Definitions volume of IEEE Std 1003.1-2001, <pthread.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.opengroup.org/unix/online.html .