add pthread_cancel, obtained from OpenBSD.

eischen (Daniel Eischen) added wrappers to protect against cancled
threads orphaning internal resources.

the cancelability code is still a bit fuzzy but works for test
programs of my own, OpenBSD's and some examples from ORA's books.

add readdir_r to both libc and libc_r

add some 'const' attributes to function parameters

Reviewed by: eischen, jasone

1 files changed, 70 insertions, 0 deletions

diff --git a/share/man/man3/pthread_cancel.3 b/share/man/man3/pthread_cancel.3
new file mode 100644
index 0000000..5755f89
--- /dev/null
+++ b/share/man/man3/pthread_cancel.3
@@ -0,0 +1,70 @@
+.\" $FreeBSD$
+.Dd January 17, 1999
+.Dt PTHREAD_CANCEL 3
+.Os
+.Sh NAME
+.Nm pthread_cancel
+.Nd cancel execution of a thread
+.Sh SYNOPSIS
+.Fd #include <pthread.h>
+.Ft int
+.Fn pthread_cancel "pthread_t thread"
+.Sh DESCRIPTION
+The
+.Fn pthread_cancel
+function requests that
+.Fa thread
+be canceled. The target thread's cancelability state and type determines
+when the cancellation takes effect. When the cancellation is acted on,
+the cancellation cleanup handlers for
+.Fa thread
+are called. When the last cancellation cleanup handler returns,
+the thread-specific data destructor functions will be called for
+.Fa thread .
+When the last destructor function returns,
+.Fa thread
+will be terminated.
+.Pp
+The cancellation processing in the target thread runs asynchronously with
+respect to the calling thread returning from
+.Fn pthread_cancel .
+.Pp
+A status of
+.Dv PTHREAD_CANCELED
+is made available to any threads joining with the target. The symbolic
+constant
+.Dv PTHREAD_CANCELED
+expands to a constant expression of type
+.Ft "(void *)" ,
+whose value matches no pointer to an object in memory nor the value
+.Dv NULL .
+.Sh RETURN VALUES
+If successful,  the
+.Fn pthread_cancel
+functions will return zero. Otherwise an error number will be returned to
+indicate the error.
+.Sh ERRORS
+.Fn pthread_cancel
+will fail if:
+.Bl -tag -width Er
+.It Bq Er ESRCH
+No thread could be found corresponding to that specified by the given
+thread ID.
+.El
+.Sh SEE ALSO
+.Xr pthread_cleanup_pop 3 ,
+.Xr pthread_cleanup_push 3 ,
+.Xr pthread_exit 3 ,
+.Xr pthread_join 3 ,
+.Xr pthread_setcancelstate 3 ,
+.Xr pthread_setcanceltype 3 ,
+.Xr pthread_testcancel 3
+.Sh STANDARDS
+.Fn pthread_cancel
+conforms to ISO/IEC 9945-1 ANSI/IEEE
+.Pq Dq Tn POSIX
+Std 1003.1 Second Edition 1996-07-12.
+.Sh AUTHORS
+This man page was written by
+.An David Leonard <d@openbsd.org> 
+for the OpenBSD implementation of pthread_cancel.