cancel-thread can take arguments

* doc/ref/api-scheduling.texi (Threads):
* module/ice-9/threads.scm (cancel-thread): Additional args to
  cancel-thread will be returned by the thread.

doc/ref/api-scheduling.texi

@@ -112,12 +112,13 @@ If one or more threads are waiting to execute, calling yield forces an
 immediate context switch to one of them. Otherwise, yield has no effect.
 @end deffn
 
-@deffn {Scheme Procedure} cancel-thread thread
+@deffn {Scheme Procedure} cancel-thread thread . values
 @deffnx {C Function} scm_cancel_thread (thread)
 Asynchronously interrupt @var{thread} and ask it to terminate.
 @code{dynamic-wind} post thunks will run, but throw handlers will not.
 If @var{thread} has already terminated or been signaled to terminate,
-this function is a no-op.
+this function is a no-op.  Calling @code{join-thread} on the thread will
+return the given @var{values}, if the cancel succeeded.
 
 Under this hood, thread cancellation uses @code{system-async-mark} and
 @code{abort-to-prompt}.  @xref{Asyncs} for more on asynchronous

module/ice-9/threads.scm

@@ -88,16 +88,17 @@
 
 
 (define cancel-tag (make-prompt-tag "cancel"))
-(define (cancel-thread thread)
+(define (cancel-thread thread . values)
   "Asynchronously interrupt the target @var{thread} and ask it to
-terminate.  @code{dynamic-wind} post thunks will run, but throw handlers
+terminate, returning the given @var{values}.  @code{dynamic-wind} post
-will not.  If @var{thread} has already terminated or been signaled to
+thunks will run, but throw handlers will not.  If @var{thread} has
-terminate, this function is a no-op."
+already terminated or been signaled to terminate, this function is a
+no-op."
   (system-async-mark
    (lambda ()
      (catch #t
        (lambda ()
-         (abort-to-prompt cancel-tag))
+         (apply abort-to-prompt cancel-tag values))
        (lambda _
          (error "thread cancellation failed, throwing error instead???"))))
    thread))