if (wroteSome) {
	    return errorCode;
	} else if (statePtr->outQueueHead == NULL) {
	    ResetFlag(statePtr, BG_FLUSH_SCHEDULED);
	    (chanPtr->typePtr->watchProc)(chanPtr->instanceData,
		    statePtr->interestMask);
	} else {

	    /*
	     * When we are calledFromAsyncFlush, that means a writable
	     * state on the channel triggered the call, so we should be
	     * able to write something.  Either we did write something 
	     * and wroteSome should be set, or there was nothing left to
	     * write in this call, and we've completed the BG flush.
	     * These are the two cases above.  If we get here, that means
	     * there is some kind failure in the writable event machinery.
	     */



	    assert(!calledFromAsyncFlush);
	}
    }

    /*
     * If the channel is flagged as closed, delete it when the refCount drops
     * to zero, the output queue is empty and there is no output in the
     * current output buffer.

} "ready line1 line2 {done\n}"
test io-53.4 {CopyData: background write overflow} {stdio unix openpipe fileevent fcopy} {
    set big bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb\n
    variable x
    for {set x 0} {$x < 12} {incr x} {
	append big $big
    }

    file delete $path(pipe)
    set f1 [open $path(pipe) w]
    puts $f1 {
	puts ready
	fcopy stdin stdout -command { set x }
	vwait x




    }
    close $f1
    set f1 [open "|[list [interpreter] $path(pipe)]" r+]
    set result [gets $f1]
    fconfigure $f1 -blocking 0
    puts $f1 $big
    flush $f1

    set result ""
    fileevent $f1 read [namespace code {
	append result [read $f1 1024]
	if {[string length $result] >= [string length $big]} {
	    set x done
	}
    }]

{
    PipeState *psPtr = (PipeState *) instanceData;
    int newmask;

    if (psPtr->inFile) {
	newmask = mask & (TCL_READABLE | TCL_EXCEPTION);
	if (newmask) {
	    Tcl_CreateFileHandler(GetFd(psPtr->inFile), newmask,
		    (Tcl_FileProc *) Tcl_NotifyChannel,
		    (ClientData) psPtr->channel);
	} else {
	    Tcl_DeleteFileHandler(GetFd(psPtr->inFile));
	}
    }
    if (psPtr->outFile) {
	newmask = mask & (TCL_WRITABLE | TCL_EXCEPTION);
	if (newmask) {
	    Tcl_CreateFileHandler(GetFd(psPtr->outFile), newmask,
		    (Tcl_FileProc *) Tcl_NotifyChannel,
		    (ClientData) psPtr->channel);
	} else {
	    Tcl_DeleteFileHandler(GetFd(psPtr->outFile));
	}
    }
}