[PATCH] Cygwin: pty: Revise code waiting for forwarding again.

[Takashi Yano <takashi dot yano at nifty dot ne dot jp>]

- After commit 6cc299f0e20e4b76f7dbab5ea8c296ffa4859b62, outputs of
  cygwin programs which call both printf() and WriteConsole() are
  frequently distorted. This patch reverts waiting function to dumb
  Sleep().
---
 winsup/cygwin/fhandler_tty.cc | 30 +++++++++++++++++++-----------
 winsup/cygwin/tty.cc          |  3 ++-
 winsup/cygwin/tty.h           |  3 ++-
 3 files changed, 23 insertions(+), 13 deletions(-)

diff --git a/winsup/cygwin/fhandler_tty.cc b/winsup/cygwin/fhandler_tty.cc
index 1710f2520..404216bf6 100644
--- a/winsup/cygwin/fhandler_tty.cc
+++ b/winsup/cygwin/fhandler_tty.cc
@@ -1109,7 +1109,9 @@ skip_console_setting:
     }
   else if ((fd == 1 || fd == 2) && !get_ttyp ()->switch_to_pcon_out)
     {
-      cygwait (get_ttyp ()->fwd_done, INFINITE);
+      DWORD elasped = GetTickCount () - get_ttyp ()->last_push_time;
+      if (elasped < get_ttyp ()->max_fwd_latency)
+	Sleep (get_ttyp ()->max_fwd_latency - elasped);
       if (get_ttyp ()->pcon_pid == 0 ||
 	  kill (get_ttyp ()->pcon_pid, 0) != 0)
 	get_ttyp ()->pcon_pid = myself->pid;
@@ -1151,8 +1153,7 @@ fhandler_pty_slave::reset_switch_to_pcon (void)
       SetConsoleMode (get_handle (), mode & ~ENABLE_ECHO_INPUT);
     }
   if (get_ttyp ()->switch_to_pcon_out)
-    /* Wait for pty_master_fwd_thread() */
-    cygwait (get_ttyp ()->fwd_done, INFINITE);
+    Sleep (get_ttyp ()->max_fwd_latency);
   get_ttyp ()->pcon_pid = 0;
   get_ttyp ()->switch_to_pcon_in = false;
   get_ttyp ()->switch_to_pcon_out = false;
@@ -1187,6 +1188,8 @@ fhandler_pty_slave::push_to_pcon_screenbuffer (const char *ptr, size_t len)
     if (!try_reattach_pcon ())
       goto detach;
 
+  get_ttyp ()->last_push_time = GetTickCount ();
+
   char *buf;
   size_t nlen;
   DWORD origCP;
@@ -2210,8 +2213,6 @@ fhandler_pty_master::close ()
 	    }
 	  release_output_mutex ();
 	  master_fwd_thread->terminate_thread ();
-	  CloseHandle (get_ttyp ()->fwd_done);
-	  get_ttyp ()->fwd_done = NULL;
 	}
     }
 
@@ -2728,7 +2729,11 @@ fhandler_pty_slave::fixup_after_attach (bool native_maybe, int fd_set)
 	      DWORD mode = ENABLE_PROCESSED_OUTPUT | ENABLE_WRAP_AT_EOL_OUTPUT;
 	      SetConsoleMode (get_output_handle (), mode);
 	      if (!get_ttyp ()->switch_to_pcon_out)
-		cygwait (get_ttyp ()->fwd_done, INFINITE);
+		{
+		  DWORD elasped = GetTickCount () - get_ttyp ()->last_push_time;
+		  if (elasped < get_ttyp ()->max_fwd_latency)
+		    Sleep (get_ttyp ()->max_fwd_latency - elasped);
+		}
 	      if (get_ttyp ()->pcon_pid == 0 ||
 		  kill (get_ttyp ()->pcon_pid, 0) != 0)
 		get_ttyp ()->pcon_pid = myself->pid;
@@ -3010,14 +3015,12 @@ fhandler_pty_master::pty_master_fwd_thread ()
   termios_printf ("Started.");
   for (;;)
     {
-      if (::bytes_available (rlen, from_slave) && rlen == 0)
-	SetEvent (get_ttyp ()->fwd_done);
       if (!ReadFile (from_slave, outbuf, sizeof outbuf, &rlen, NULL))
 	{
 	  termios_printf ("ReadFile for forwarding failed, %E");
 	  break;
 	}
-      ResetEvent (get_ttyp ()->fwd_done);
+
       ssize_t wlen = rlen;
       char *ptr = outbuf;
       if (get_pseudo_console ())
@@ -3025,7 +3028,13 @@ fhandler_pty_master::pty_master_fwd_thread ()
 	  /* Avoid duplicating slave output which is already sent to
 	     to_master_cyg */
 	  if (!get_ttyp ()->switch_to_pcon_out)
-	    continue;
+	    {
+	      DWORD elasped = GetTickCount () - get_ttyp ()->last_push_time;
+	      if (get_ttyp ()->last_push_time &&
+		  elasped > get_ttyp ()->max_fwd_latency)
+		get_ttyp ()->max_fwd_latency = elasped;
+	      continue;
+	    }
 
 	  /* Avoid setting window title to "cygwin-console-helper.exe" */
 	  int state = 0;
@@ -3380,7 +3389,6 @@ fhandler_pty_master::setup ()
       errstr = "pty master forwarding thread";
       goto err;
     }
-  get_ttyp ()->fwd_done = CreateEvent (&sec_none, true, false, NULL);
 
   setup_pseudoconsole ();
 
diff --git a/winsup/cygwin/tty.cc b/winsup/cygwin/tty.cc
index ef9bbc1ff..b290a41e1 100644
--- a/winsup/cygwin/tty.cc
+++ b/winsup/cygwin/tty.cc
@@ -245,7 +245,8 @@ tty::init ()
   num_pcon_attached_slaves = 0;
   term_code_page = 0;
   need_redraw_screen = false;
-  fwd_done = NULL;
+  max_fwd_latency = 20;
+  last_push_time = 0;
 }
 
 HANDLE
diff --git a/winsup/cygwin/tty.h b/winsup/cygwin/tty.h
index b291fd3c1..ba2b9074a 100644
--- a/winsup/cygwin/tty.h
+++ b/winsup/cygwin/tty.h
@@ -106,7 +106,8 @@ private:
   int num_pcon_attached_slaves;
   UINT term_code_page;
   bool need_redraw_screen;
-  HANDLE fwd_done;
+  DWORD max_fwd_latency;
+  DWORD last_push_time;
 
 public:
   HANDLE from_master () const { return _from_master; }
-- 
2.21.0