[newlib-cygwin] Cygwin: FIFO: avoid deadlock when closing

[Ken Brown]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=d1b36ea949e275c803787523b0b04657895638fc

commit d1b36ea949e275c803787523b0b04657895638fc
Author: Ken Brown <kbrown@cornell.edu>
Date:   Sat Jun 22 13:58:12 2019 -0400

    Cygwin: FIFO: avoid deadlock when closing
    
    fhandler_fifo::close could be called from a signal handler or another
    thread at a time when another function is holding the fifo_client
    lock.  This could prevent the listen_client thread from acting on the
    thread termination event.  Avoid a deadlock by calling
    fifo_client_unlock at the beginning of fhandler_fifo::close.

Diff:
---
 winsup/cygwin/fhandler_fifo.cc | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/winsup/cygwin/fhandler_fifo.cc b/winsup/cygwin/fhandler_fifo.cc
index 4291a7e..8afa397 100644
--- a/winsup/cygwin/fhandler_fifo.cc
+++ b/winsup/cygwin/fhandler_fifo.cc
@@ -928,6 +928,9 @@ fhandler_fifo::stop_listen_client ()
 int
 fhandler_fifo::close ()
 {
+  /* Avoid deadlock with lct in case this is called from a signal
+     handler or another thread. */
+  fifo_client_unlock ();
   int ret = stop_listen_client ();
   if (read_ready)
     CloseHandle (read_ready);