Cygwin: pty: Add a workaround for issue of starting a lot of mintty.

- If a lot of mintty are started in a short time from a mintty, some
  of them hang with empty screen, crash immediately or hang on exiting
  mintty. The following report seems to be related to this issue.
    https://cygwin.com/pipermail/cygwin/2020-August/245751.html
  The cause is not clear at all, but this patch seems to solve the
  issue.

1 files changed, 11 insertions, 4 deletions

diff --git a/winsup/cygwin/spawn.cc b/winsup/cygwin/spawn.cc
index 840ec4a86..e70ceb86d 100644
--- a/winsup/cygwin/spawn.cc
+++ b/winsup/cygwin/spawn.cc
@@ -177,7 +177,7 @@ find_exec (const char *name, path_conv& buf, const char *search,
 /* Utility for child_info_spawn::worker.  */
 
 static HANDLE
-handle (int fd, bool writing)
+handle (int fd, bool writing, bool iscygwin)
 {
   HANDLE h;
   cygheap_fdget cfd (fd);
@@ -188,6 +188,11 @@ handle (int fd, bool writing)
     h = INVALID_HANDLE_VALUE;
   else if (!writing)
     h = cfd->get_handle ();
+  else if (cfd->get_major () == DEV_PTYS_MAJOR && iscygwin)
+    {
+      fhandler_pty_slave *ptys = (fhandler_pty_slave *)(fhandler_base *) cfd;
+      h = ptys->get_output_handle_cyg ();
+    }
   else
     h = cfd->get_output_handle ();
 
@@ -625,9 +630,11 @@ child_info_spawn::worker (const char *prog_arg, const char *const *argv,
 
       /* Set up needed handles for stdio */
       si.dwFlags = STARTF_USESTDHANDLES;
-      si.hStdInput = handle ((in__stdin < 0 ? 0 : in__stdin), false);
-      si.hStdOutput = handle ((in__stdout < 0 ? 1 : in__stdout), true);
-      si.hStdError = handle (2, true);
+      si.hStdInput = handle ((in__stdin < 0 ? 0 : in__stdin), false,
+			     iscygwin ());
+      si.hStdOutput = handle ((in__stdout < 0 ? 1 : in__stdout), true,
+			      iscygwin ());
+      si.hStdError = handle (2, true, iscygwin ());
 
       si.cb = sizeof (si);