132fb3dc99
The function allows to peek at the thread exit status and even see return value, without joining (and thus finally destroying) the target thread. Reviewed by: markj Sponsored by: The FreeBSD Foundation (kib) MFC after: 2 weeks Differential revision: https://reviews.freebsd.org/D23676
175 lines
4.9 KiB
Groff
175 lines
4.9 KiB
Groff
.\" Copyright (c) 1996-1998 John Birrell <jb@cimlogic.com.au>.
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by John Birrell.
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.\" 4. Neither the name of the author nor the names of any co-contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd February 13, 2019
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.Dt PTHREAD_JOIN 3
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.Os
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.Sh NAME
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.Nm pthread_join ,
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.Nm pthread_peekjoin_np ,
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.Nm pthread_timedjoin_np
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.Nd inspect thread termination state
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.Sh LIBRARY
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.Lb libpthread
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.Sh SYNOPSIS
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.In pthread.h
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.Ft int
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.Fn pthread_join "pthread_t thread" "void **value_ptr"
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.In pthread_np.h
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.Ft int
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.Fo pthread_peekjoin_np
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.Fa "pthread_t thread"
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.Fa "void **value_ptr"
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.Fc
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.Ft int
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.Fo pthread_timedjoin_np
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.Fa "pthread_t thread"
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.Fa "void **value_ptr"
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.Fa "const struct timespec *abstime"
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.Fc
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.Sh DESCRIPTION
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The
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.Fn pthread_join
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function suspends execution of the calling thread until the target
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.Fa thread
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terminates unless the target
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.Fa thread
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has already terminated.
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.Pp
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On return from a successful
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.Fn pthread_join
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call with a non-NULL
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.Fa value_ptr
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argument, the value passed to
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.Fn pthread_exit
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by the terminating thread is stored in the location referenced by
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.Fa value_ptr .
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When a
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.Fn pthread_join
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returns successfully, the target thread has been terminated.
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The results
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of multiple simultaneous calls to
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.Fn pthread_join
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specifying the same target thread are undefined.
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If the thread calling
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.Fn pthread_join
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is cancelled, then the target thread is not detached.
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.Pp
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The
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.Fn pthread_timedjoin_np
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function is equivalent to the
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.Fn pthread_join
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function except it will return
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.Er ETIMEDOUT
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if target thread does not exit before specified absolute time passes.
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.Pp
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The
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.Fn pthread_peekjoin_np
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only peeks into the exit status of the specified thread.
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If the thread has not exited, the
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.Er EBUSY
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error is returned.
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Otherwise, zero is returned and the thread exit value is optionally stored
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into the location of
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.Fa *value_ptr .
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The target thread is left unjoined and can be used as an argument for
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the
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.Fn pthread_join
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family of functions again.
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.Pp
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A thread that has exited but remains unjoined counts against
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[_POSIX_THREAD_THREADS_MAX].
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.Sh RETURN VALUES
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If successful, the described functions return zero.
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Otherwise an error number is returned to indicate the error or
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special condition.
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.Sh ERRORS
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The
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.Fn pthread_join ,
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.Fn pthread_peekjoin_np ,
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and
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.Fn pthread_timedjoin_np
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functions will fail if:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The implementation has detected that the value specified by
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.Fa thread
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does not refer to a joinable thread.
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.It Bq Er ESRCH
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No thread could be found corresponding to that specified by the given
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thread ID,
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.Fa thread .
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.It Bq Er EDEADLK
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A deadlock was detected or the value of
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.Fa thread
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specifies the calling thread.
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.It Bq Er EOPNOTSUPP
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The implementation detected that another caller is already waiting on
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.Fa thread .
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.El
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.Pp
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Additionally, the
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.Fn pthread_timedjoin_np
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function will fail if:
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.Bl -tag -width Er
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.It Bq Er ETIMEDOUT
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The specified absolute time passed while
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.Fn pthread_timedjoin_np
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waited for thread exit.
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.El
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.Pp
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The
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.Fn pthread_peekjoin_np
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function will also fail if:
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.Bl -tag -width Er
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.It Bq Er EBUSY
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The specified thread has not yet exited.
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.El
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.Sh SEE ALSO
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.Xr wait 2 ,
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.Xr pthread_create 3
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.Sh STANDARDS
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The
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.Fn pthread_join
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function conforms to
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.St -p1003.1-96 .
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The
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.Fn pthread_timedjoin_np
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function is a
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.Fx
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extension which first appeared in
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.Fx 6.1 .
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Another extension, the
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.Fn pthread_peekjoin_np
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function, first appearead in
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.Fx 13.0 .
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