HardenedBSD/share/man/man3/pthread_join.3

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.Dd October 12, 2021
.Dt PTHREAD_JOIN 3
.Os
.Sh NAME
.Nm pthread_join ,
.Nm pthread_peekjoin_np ,
.Nm pthread_timedjoin_np
.Nd inspect thread termination state
.Sh LIBRARY
.Lb libpthread
.Sh SYNOPSIS
.In pthread.h
.Ft int
.Fn pthread_join "pthread_t thread" "void **value_ptr"
.In pthread_np.h
.Ft int
.Fo pthread_peekjoin_np
.Fa "pthread_t thread"
.Fa "void **value_ptr"
.Fc
.Ft int
.Fo pthread_timedjoin_np
.Fa "pthread_t thread"
.Fa "void **value_ptr"
.Fa "const struct timespec *abstime"
.Fc
.Sh DESCRIPTION
The
.Fn pthread_join
function suspends execution of the calling thread until the target
.Fa thread
terminates unless the target
.Fa thread
has already terminated.
.Pp
On return from a successful
.Fn pthread_join
call with a non-NULL
.Fa value_ptr
argument, the value passed to
.Fn pthread_exit
by the terminating thread is stored in the location referenced by
.Fa value_ptr .
When a
.Fn pthread_join
returns successfully, the target thread has been terminated.
The results
of multiple simultaneous calls to
.Fn pthread_join
specifying the same target thread are undefined.
If the thread calling
.Fn pthread_join
is cancelled, then the target thread is not detached.
.Pp
The
.Fn pthread_timedjoin_np
function is equivalent to the
.Fn pthread_join
function except it will return
.Er ETIMEDOUT
if target thread does not exit before specified absolute time passes.
.Pp
The
.Fn pthread_peekjoin_np
only peeks into the exit status of the specified thread.
If the thread has not exited, the
.Er EBUSY
error is returned.
Otherwise, zero is returned and the thread exit value is optionally stored
into the location of
.Fa *value_ptr .
The target thread is left unjoined and can be used as an argument for
the
.Fn pthread_join
family of functions again.
.Pp
A thread that has exited but remains unjoined counts against
[_POSIX_THREAD_THREADS_MAX].
.Sh RETURN VALUES
If successful, the described functions return zero.
Otherwise an error number is returned to indicate the error or
special condition.
.Sh ERRORS
The
.Fn pthread_join ,
.Fn pthread_peekjoin_np ,
and
.Fn pthread_timedjoin_np
functions will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
The implementation has detected that the value specified by
.Fa thread
does not refer to a joinable thread.
.It Bq Er ESRCH
No thread could be found corresponding to that specified by the given
thread ID,
.Fa thread .
.It Bq Er EDEADLK
A deadlock was detected or the value of
.Fa thread
specifies the calling thread.
.It Bq Er EOPNOTSUPP
The implementation detected that another caller is already waiting on
.Fa thread .
.El
.Pp
Additionally, the
.Fn pthread_timedjoin_np
function will fail if:
.Bl -tag -width Er
.It Bq Er ETIMEDOUT
The specified absolute time passed while
.Fn pthread_timedjoin_np
waited for thread exit.
.El
.Pp
The
.Fn pthread_peekjoin_np
function will also fail if:
.Bl -tag -width Er
.It Bq Er EBUSY
The specified thread has not yet exited.
.El
.Sh SEE ALSO
.Xr wait 2 ,
.Xr pthread 3 ,
.Xr pthread_create 3 ,
.Xr pthread_np 3
.Sh STANDARDS
The
.Fn pthread_join
function conforms to
.St -p1003.1-96 .
The
.Fn pthread_timedjoin_np
function is a
.Fx
extension which first appeared in
.Fx 6.1 .
Another extension, the
.Fn pthread_peekjoin_np
function, first appearead in
.Fx 13.0 .