[newlib-cygwin] Cygwin: pty: Add missing guard for close_pseudoconsole().

[Corinna Vinschen]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=6d46d8504948b365cd5365e0f62f855f98773031

commit 6d46d8504948b365cd5365e0f62f855f98773031
Author: Takashi Yano <takashi.yano@nifty.ne.jp>
Date:   Wed Apr 21 12:07:31 2021 +0900

    Cygwin: pty: Add missing guard for close_pseudoconsole().
    
    - This patch adds a missing mutex guard for close_pseudoconsole()
      call when GDB exits.

Diff:
---
 winsup/cygwin/fhandler_tty.cc | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/winsup/cygwin/fhandler_tty.cc b/winsup/cygwin/fhandler_tty.cc
index 530321513..9c03e09a7 100644
--- a/winsup/cygwin/fhandler_tty.cc
+++ b/winsup/cygwin/fhandler_tty.cc
@@ -177,7 +177,9 @@ atexit_func (void)
 						    input_available_event);
 		ReleaseMutex (ptys->input_mutex);
 	      }
+	    WaitForSingleObject (ptys->pcon_mutex, INFINITE);
 	    ptys->close_pseudoconsole (ttyp, force_switch_to);
+	    ReleaseMutex (ptys->pcon_mutex);
 	    break;
 	  }
       CloseHandle (h_gdb_process);