Cygwin: pty: Allow multiple apps to enable pseudo console simultaneously.

- After commit bb428520, there has been the disadvantage:
  7) Pseudo console cannot be activated if it is already activated for
     another process on same pty.
  This patch clears this disadvantage.

6 files changed, 314 insertions, 93 deletions

diff --git a/winsup/cygwin/fhandler.h b/winsup/cygwin/fhandler.h
index 3db33ea78..a4c1a3816 100644
--- a/winsup/cygwin/fhandler.h
+++ b/winsup/cygwin/fhandler.h
@@ -2273,6 +2273,9 @@ class fhandler_pty_common: public fhandler_termios
   }
 
   void resize_pseudo_console (struct winsize *);
+  static DWORD get_console_process_id (DWORD pid, bool match,
+				       bool cygwin = false,
+				       bool stub_only = false);
 
  protected:
   static BOOL process_opost_output (HANDLE h, const void *ptr, ssize_t& len,
@@ -2354,14 +2357,14 @@ class fhandler_pty_slave: public fhandler_pty_common
   bool term_has_pcon_cap (const WCHAR *env);
   void set_switch_to_pcon (void);
   void reset_switch_to_pcon (void);
-  void mask_switch_to_pcon_in (bool mask);
+  void mask_switch_to_pcon_in (bool mask, bool xfer);
   void setup_locale (void);
   tty *get_ttyp () { return (tty *) tc (); } /* Override as public */
   void create_invisible_console (void);
   static void transfer_input (xfer_dir dir, HANDLE from, tty *ttyp,
 			      _minor_t unit, HANDLE input_available_event);
   HANDLE get_input_available_event (void) { return input_available_event; }
-  bool pcon_activated (void) { return get_ttyp ()->h_pseudo_console; }
+  bool pcon_activated (void) { return get_ttyp ()->pcon_activated; }
 };
 
 #define __ptsname(buf, unit) __small_sprintf ((buf), "/dev/pty%d", (unit))
diff --git a/winsup/cygwin/fhandler_tty.cc b/winsup/cygwin/fhandler_tty.cc
index c74e38c3d..06fc19ac2 100644
--- a/winsup/cygwin/fhandler_tty.cc
+++ b/winsup/cygwin/fhandler_tty.cc
@@ -64,8 +64,9 @@ struct pipe_reply {
 
 extern HANDLE attach_mutex; /* Defined in fhandler_console.cc */
 
-static DWORD
-get_console_process_id (DWORD pid, bool match)
+DWORD
+fhandler_pty_common::get_console_process_id (DWORD pid, bool match,
+					     bool cygwin, bool stub_only)
 {
   tmp_pathbuf tp;
   DWORD *list = (DWORD *) tp.c_get ();
@@ -75,16 +76,34 @@ get_console_process_id (DWORD pid, bool match)
   if (num == 0 || num > buf_size)
     return 0;
 
-  DWORD res = 0;
+  DWORD res_pri = 0, res = 0;
   /* Last one is the oldest. */
   /* https://github.com/microsoft/terminal/issues/95 */
   for (int i = (int) num - 1; i >= 0; i--)
     if ((match && list[i] == pid) || (!match && list[i] != pid))
       {
-	res = list[i];
-	break;
+	if (!cygwin)
+	  {
+	    res_pri = list[i];
+	    break;
+	  }
+	else
+	  {
+	    pinfo p (cygwin_pid (list[i]));
+	    if (!!p && p->dwProcessId && p->exec_dwProcessId
+		&& p->dwProcessId != p->exec_dwProcessId)
+	      {
+		res_pri = list[i];
+		break;
+	      }
+	    if (!!p && !res)
+	      res = list[i];
+	  }
       }
-  return res;
+  if (stub_only)
+    return res_pri;
+  else
+    return res_pri ?: res;
 }
 
 static bool isHybrid;
@@ -937,7 +956,7 @@ fhandler_pty_slave::init (HANDLE h, DWORD a, mode_t)
 void
 fhandler_pty_slave::set_switch_to_pcon (void)
 {
-  if (!get_ttyp ()->switch_to_pcon_in)
+  if (!isHybrid)
     {
       isHybrid = true;
       setup_locale ();
@@ -964,9 +983,10 @@ fhandler_pty_slave::reset_switch_to_pcon (void)
 	{
 	  CloseHandle (h_gdb_process);
 	  h_gdb_process = NULL;
-	  if (isHybrid && get_ttyp ()->pcon_pid == myself->pid)
+	  if (isHybrid)
 	    {
-	      if (get_ttyp ()->switch_to_pcon_in)
+	      if (get_ttyp ()->switch_to_pcon_in
+		  && get_ttyp ()->pcon_pid == myself->pid)
 		fhandler_pty_slave::transfer_input (fhandler_pty_slave::to_cyg,
 						    get_handle (),
 						    get_ttyp (), get_minor (),
@@ -976,7 +996,7 @@ fhandler_pty_slave::reset_switch_to_pcon (void)
 		   the console of the parent process will fail.
 		   Therefore, never close pseudo console here. */
 		return;
-	      bool need_restore_handles = !!get_ttyp ()->h_pseudo_console;
+	      bool need_restore_handles = get_ttyp ()->pcon_activated;
 	      close_pseudoconsole (get_ttyp ());
 	      if (need_restore_handles)
 		{
@@ -1027,11 +1047,8 @@ fhandler_pty_slave::reset_switch_to_pcon (void)
 		  if (fix_err)
 		    SetStdHandle (STD_ERROR_HANDLE, get_output_handle ());
 		}
-	      get_ttyp ()->pcon_pid = 0;
-	      get_ttyp ()->switch_to_pcon_in = false;
+	      isHybrid = false;
 	    }
-	  isHybrid = false;
-	  return;
 	}
     }
   if (get_ttyp ()->pcon_pid && get_ttyp ()->pcon_pid != myself->pid
@@ -1040,14 +1057,14 @@ fhandler_pty_slave::reset_switch_to_pcon (void)
     return;
   if (isHybrid)
     return;
-  if (get_ttyp ()->switch_to_pcon_in && !get_ttyp ()->h_pseudo_console)
+  if (get_ttyp ()->switch_to_pcon_in && !get_ttyp ()->pcon_activated)
     fhandler_pty_slave::transfer_input (fhandler_pty_slave::to_cyg,
 					get_handle (),
 					get_ttyp (), get_minor (),
 					input_available_event);
   get_ttyp ()->pcon_pid = 0;
   get_ttyp ()->switch_to_pcon_in = false;
-  get_ttyp ()->h_pseudo_console = NULL;
+  get_ttyp ()->pcon_activated = false;
 }
 
 ssize_t __stdcall
@@ -1087,7 +1104,7 @@ fhandler_pty_slave::write (const void *ptr, size_t len)
 }
 
 void
-fhandler_pty_slave::mask_switch_to_pcon_in (bool mask)
+fhandler_pty_slave::mask_switch_to_pcon_in (bool mask, bool xfer)
 {
   char name[MAX_PATH];
   shared_name (name, TTY_SLAVE_READING, get_minor ());
@@ -1102,21 +1119,63 @@ fhandler_pty_slave::mask_switch_to_pcon_in (bool mask)
   else if (InterlockedDecrement (&num_reader) == 0)
     CloseHandle (slave_reading);
 
-  if (get_ttyp ()->switch_to_pcon_in
-      && (get_ttyp ()->pcon_pid == myself->pid
-	  || !get_ttyp ()->h_pseudo_console)
-      && !!masked != mask)
-    {
+  if (get_ttyp ()->switch_to_pcon_in && !!masked != mask && xfer)
+    { /* Transfer input */
+      bool attach_restore = false;
+      DWORD pcon_winpid = 0;
+      if (get_ttyp ()->pcon_pid)
+	{
+	  pinfo p (get_ttyp ()->pcon_pid);
+	  if (p)
+	    pcon_winpid = p->exec_dwProcessId ?: p->dwProcessId;
+	}
       if (mask)
-	fhandler_pty_slave::transfer_input (fhandler_pty_slave::to_cyg,
-					    get_handle (),
-					    get_ttyp (), get_minor (),
-					    input_available_event);
+	{
+	  HANDLE from = get_handle ();
+	  if (get_ttyp ()->pcon_activated && pcon_winpid
+	      && !get_console_process_id (pcon_winpid, true))
+	    {
+	      HANDLE pcon_owner =
+		OpenProcess (PROCESS_DUP_HANDLE, FALSE, pcon_winpid);
+	      DuplicateHandle (pcon_owner, get_ttyp ()->h_pcon_in,
+			       GetCurrentProcess (), &from,
+			       0, TRUE, DUPLICATE_SAME_ACCESS);
+	      CloseHandle (pcon_owner);
+	      FreeConsole ();
+	      AttachConsole (pcon_winpid);
+	      attach_restore = true;
+	    }
+	  fhandler_pty_slave::transfer_input (fhandler_pty_slave::to_cyg,
+					      from,
+					      get_ttyp (), get_minor (),
+					      input_available_event);
+	}
       else
-	fhandler_pty_slave::transfer_input (fhandler_pty_slave::to_nat,
-					    get_handle_cyg (),
-					    get_ttyp (), get_minor (),
-					    input_available_event);
+	{
+	  if (get_ttyp ()->pcon_activated && pcon_winpid
+	      && !get_console_process_id (pcon_winpid, true))
+	    {
+	      FreeConsole ();
+	      AttachConsole (pcon_winpid);
+	      attach_restore = true;
+	    }
+	  fhandler_pty_slave::transfer_input (fhandler_pty_slave::to_nat,
+					      get_handle_cyg (),
+					      get_ttyp (), get_minor (),
+					      input_available_event);
+	}
+      if (attach_restore)
+	{
+	  FreeConsole ();
+	  pinfo p (myself->ppid);
+	  if (p)
+	    {
+	      if (!AttachConsole (p->dwProcessId))
+		AttachConsole (ATTACH_PARENT_PROCESS);
+	    }
+	  else
+	    AttachConsole (ATTACH_PARENT_PROCESS);
+	}
     }
   return;
 }
@@ -1143,6 +1202,7 @@ fhandler_pty_slave::read (void *ptr, size_t& len)
   DWORD bytes_in_pipe;
   char buf[INP_BUFFER_SIZE];
   DWORD time_to_wait;
+  char *ptr0 = (char *) ptr;
 
   bg_check_types bg = bg_check (SIGTTIN);
   if (bg <= bg_eof)
@@ -1157,7 +1217,7 @@ fhandler_pty_slave::read (void *ptr, size_t& len)
 
   if (ptr) /* Indicating not tcflush(). */
     {
-      mask_switch_to_pcon_in (true);
+      mask_switch_to_pcon_in (true, true);
       reset_switch_to_pcon ();
     }
 
@@ -1271,7 +1331,7 @@ fhandler_pty_slave::read (void *ptr, size_t& len)
       if (ptr && !bytes_in_pipe && !vmin && !time_to_wait)
 	{
 	  ReleaseMutex (input_mutex);
-	  mask_switch_to_pcon_in (false);
+	  mask_switch_to_pcon_in (false, false);
 	  len = (size_t) bytes_in_pipe;
 	  return;
 	}
@@ -1376,7 +1436,7 @@ fhandler_pty_slave::read (void *ptr, size_t& len)
 out:
   termios_printf ("%d = read(%p, %lu)", totalread, ptr, len);
   len = (size_t) totalread;
-  mask_switch_to_pcon_in (false);
+  mask_switch_to_pcon_in (false, totalread > 0 && ptr0[totalread - 1] == '\n');
 }
 
 int
@@ -1417,7 +1477,7 @@ fhandler_pty_slave::tcgetattr (struct termios *t)
       {
 	if (get_ttyp ()->pcon_start)
 	  t->c_lflag &= ~(ICANON | ECHO);
-	if (get_ttyp ()->h_pseudo_console)
+	if (get_ttyp ()->pcon_activated)
 	  t->c_iflag &= ~ICRNL;
 	break;
       }
@@ -1532,7 +1592,7 @@ fhandler_pty_slave::ioctl (unsigned int cmd, void *arg)
       if (get_ttyp ()->winsize.ws_row != ((struct winsize *) arg)->ws_row
 	  || get_ttyp ()->winsize.ws_col != ((struct winsize *) arg)->ws_col)
 	{
-	  if (get_ttyp ()->h_pseudo_console && get_ttyp ()->pcon_pid)
+	  if (get_ttyp ()->pcon_activated && get_ttyp ()->pcon_pid)
 	    resize_pseudo_console ((struct winsize *) arg);
 	  get_ttyp ()->arg.winsize = *(struct winsize *) arg;
 	  get_ttyp ()->winsize = *(struct winsize *) arg;
@@ -1947,7 +2007,7 @@ fhandler_pty_master::write (const void *ptr, size_t len)
 
   /* Write terminal input to to_slave pipe instead of output_handle
      if current application is native console application. */
-  if (to_be_read_from_pcon () && get_ttyp ()->h_pseudo_console)
+  if (to_be_read_from_pcon () && get_ttyp ()->pcon_activated)
     {
       tmp_pathbuf tp;
       char *buf = (char *) ptr;
@@ -2042,7 +2102,7 @@ fhandler_pty_master::tcgetattr (struct termios *t)
   /* Workaround for rlwrap v0.40 or later */
   if (get_ttyp ()->pcon_start)
     t->c_lflag &= ~(ICANON | ECHO);
-  if (get_ttyp ()->h_pseudo_console)
+  if (get_ttyp ()->pcon_activated)
     t->c_iflag &= ~ICRNL;
   return 0;
 }
@@ -2091,7 +2151,7 @@ fhandler_pty_master::ioctl (unsigned int cmd, void *arg)
       if (get_ttyp ()->winsize.ws_row != ((struct winsize *) arg)->ws_row
 	  || get_ttyp ()->winsize.ws_col != ((struct winsize *) arg)->ws_col)
 	{
-	  if (get_ttyp ()->h_pseudo_console && get_ttyp ()->pcon_pid)
+	  if (get_ttyp ()->pcon_activated && get_ttyp ()->pcon_pid)
 	    resize_pseudo_console ((struct winsize *) arg);
 	  get_ttyp ()->winsize = *(struct winsize *) arg;
 	  get_ttyp ()->kill_pgrp (SIGWINCH);
@@ -2385,7 +2445,7 @@ fhandler_pty_master::pty_master_fwd_thread (const master_fwd_thread_param_t *p)
 	}
       ssize_t wlen = rlen;
       char *ptr = outbuf;
-      if (p->ttyp->h_pseudo_console)
+      if (p->ttyp->pcon_activated)
 	{
 	  /* Avoid setting window title to "cygwin-console-helper.exe" */
 	  int state = 0;
@@ -2899,9 +2959,7 @@ fhandler_pty_slave::setup_pseudoconsole (bool nopcon)
 
   if (nopcon)
     return false;
-  if (get_ttyp ()->pcon_pid && get_ttyp ()->pcon_pid != myself->pid
-      && !!pinfo (get_ttyp ()->pcon_pid))
-    return false;
+
   /* If the legacy console mode is enabled, pseudo console seems
      not to work as expected. To determine console mode, registry
      key ForceV2 in HKEY_CURRENT_USER\Console is checked. */
@@ -2915,11 +2973,32 @@ fhandler_pty_slave::setup_pseudoconsole (bool nopcon)
       return false;
     }
 
+  HANDLE hpConIn, hpConOut;
+  acquire_output_mutex (INFINITE);
+  if (get_ttyp ()->pcon_pid && get_ttyp ()->pcon_pid != myself->pid
+      && !!pinfo (get_ttyp ()->pcon_pid) && get_ttyp ()->pcon_activated)
+    {
+      /* Attach to the pseudo console which already exits. */
+      pinfo p (get_ttyp ()->pcon_pid);
+      HANDLE pcon_owner =
+	OpenProcess (PROCESS_DUP_HANDLE, FALSE, p->exec_dwProcessId);
+      DuplicateHandle (pcon_owner, get_ttyp ()->h_pcon_in,
+		       GetCurrentProcess (), &hpConIn,
+		       0, TRUE, DUPLICATE_SAME_ACCESS);
+      DuplicateHandle (pcon_owner, get_ttyp ()->h_pcon_out,
+		       GetCurrentProcess (), &hpConOut,
+		       0, TRUE, DUPLICATE_SAME_ACCESS);
+      CloseHandle (pcon_owner);
+      FreeConsole ();
+      AttachConsole (p->dwProcessId);
+      goto skip_create;
+    }
+
   STARTUPINFOEXW si;
   PROCESS_INFORMATION pi;
   HANDLE hello, goodbye;
   HANDLE hr, hw;
-  HANDLE hpConIn, hpConOut;
+  HPCON hpcon;
 
   do
     {
@@ -2928,11 +3007,11 @@ fhandler_pty_slave::setup_pseudoconsole (bool nopcon)
 	(SHORT) get_ttyp ()->winsize.ws_row
       };
       const DWORD inherit_cursor = 1;
+      hpcon = NULL;
       SetLastError (ERROR_SUCCESS);
       HRESULT res = CreatePseudoConsole (size, get_handle (),
 					 get_output_handle (),
-					 inherit_cursor,
-					 &get_ttyp ()->h_pseudo_console);
+					 inherit_cursor, &hpcon);
       if (res != S_OK || GetLastError () == ERROR_PROC_NOT_FOUND)
 	{
 	  if (res != S_OK)
@@ -2955,9 +3034,7 @@ fhandler_pty_slave::setup_pseudoconsole (bool nopcon)
       if (!UpdateProcThreadAttribute (si.lpAttributeList,
 				      0,
 				      PROC_THREAD_ATTRIBUTE_PSEUDOCONSOLE,
-				      get_ttyp ()->h_pseudo_console,
-				      sizeof (get_ttyp ()->h_pseudo_console),
-				      NULL, NULL))
+				      hpcon, sizeof (hpcon), NULL, NULL))
 
 	goto cleanup_heap;
 
@@ -2986,6 +3063,7 @@ fhandler_pty_slave::setup_pseudoconsole (bool nopcon)
       si.StartupInfo.hStdError = NULL;
 
       get_ttyp ()->pcon_start = true;
+      get_ttyp ()->pcon_activated = true;
       if (!CreateProcessW (NULL, cmd, &sec_none, &sec_none,
 			   TRUE, EXTENDED_STARTUPINFO_PRESENT,
 			   NULL, NULL, &si.StartupInfo, &pi))
@@ -3041,7 +3119,12 @@ fhandler_pty_slave::setup_pseudoconsole (bool nopcon)
       WaitForSingleObject (pi.hProcess, INFINITE);
       CloseHandle (goodbye);
       CloseHandle (pi.hProcess);
+    }
+  while (false);
 
+skip_create:
+  do
+    {
       /* Set handle */
       if (GetStdHandle (STD_INPUT_HANDLE) == get_handle ())
 	SetStdHandle (STD_INPUT_HANDLE, hpConIn);
@@ -3072,16 +3155,29 @@ fhandler_pty_slave::setup_pseudoconsole (bool nopcon)
   if (get_ttyp ()->pcon_pid == 0 || !pinfo (get_ttyp ()->pcon_pid))
     get_ttyp ()->pcon_pid = myself->pid;
 
-  if (get_ttyp ()->h_pseudo_console && get_ttyp ()->pcon_pid == myself->pid)
+  if (hpcon && get_ttyp ()->pcon_pid == myself->pid)
     {
-      HPCON_INTERNAL *hp = (HPCON_INTERNAL *) get_ttyp ()->h_pseudo_console;
+      HPCON_INTERNAL *hp = (HPCON_INTERNAL *) hpcon;
       get_ttyp ()->h_pcon_write_pipe = hp->hWritePipe;
+      get_ttyp ()->h_pcon_condrv_reference = hp->hConDrvReference;
+      get_ttyp ()->h_pcon_conhost_process = hp->hConHostProcess;
+      DuplicateHandle (GetCurrentProcess (), hpConIn,
+		       GetCurrentProcess (), &get_ttyp ()->h_pcon_in,
+		       0, TRUE, DUPLICATE_SAME_ACCESS);
+      DuplicateHandle (GetCurrentProcess (), hpConOut,
+		       GetCurrentProcess (), &get_ttyp ()->h_pcon_out,
+		       0, TRUE, DUPLICATE_SAME_ACCESS);
+      /* Discard the pseudo console handler container here.
+	 Reconstruct it temporary when it is needed. */
+      HeapFree (GetProcessHeap (), 0, hp);
     }
 
   if (get_ttyp ()->previous_code_page)
     SetConsoleCP (get_ttyp ()->previous_code_page);
   if (get_ttyp ()->previous_output_code_page)
     SetConsoleOutputCP (get_ttyp ()->previous_output_code_page);
+
+  release_output_mutex ();
   return true;
 
 cleanup_pcon_in:
@@ -3093,6 +3189,8 @@ cleanup_helper_process:
   goto skip_close_hello;
 cleanup_event_and_pipes:
   CloseHandle (hello);
+  get_ttyp ()->pcon_start = false;
+  get_ttyp ()->pcon_activated = false;
 skip_close_hello:
   CloseHandle (goodbye);
   CloseHandle (hr);
@@ -3100,16 +3198,15 @@ skip_close_hello:
 cleanup_heap:
   HeapFree (GetProcessHeap (), 0, si.lpAttributeList);
 cleanup_pseudo_console:
-  if (get_ttyp ()->h_pseudo_console)
+  if (hpcon)
     {
-      HPCON_INTERNAL *hp = (HPCON_INTERNAL *) get_ttyp ()->h_pseudo_console;
+      HPCON_INTERNAL *hp = (HPCON_INTERNAL *) hpcon;
       HANDLE tmp = hp->hConHostProcess;
-      ClosePseudoConsole (get_ttyp ()->h_pseudo_console);
+      ClosePseudoConsole (hpcon);
       CloseHandle (tmp);
     }
 fallback:
-  get_ttyp ()->pcon_start = false;
-  get_ttyp ()->h_pseudo_console = NULL;
+  release_output_mutex ();
   return false;
 }
 
@@ -3118,20 +3215,121 @@ fallback:
 void
 fhandler_pty_slave::close_pseudoconsole (tty *ttyp)
 {
-  if (ttyp->h_pseudo_console)
+  DWORD switch_to_stub = 0, switch_to = 0;
+  DWORD new_pcon_pid = 0;
+  if (ttyp->pcon_pid == myself->pid)
+    {
+      /* Search another process which attaches to the pseudo console */
+      DWORD current_pid = myself->exec_dwProcessId ?: myself->dwProcessId;
+      switch_to =
+	get_console_process_id (current_pid, false, true);
+      if (switch_to)
+	{
+	  pinfo p (cygwin_pid (switch_to));
+	  if (p)
+	    {
+	      if (p->exec_dwProcessId)
+		switch_to_stub = p->exec_dwProcessId;
+	      new_pcon_pid = p->pid;
+	    }
+	}
+    }
+  if (ttyp->pcon_activated)
     {
       ttyp->previous_code_page = GetConsoleCP ();
       ttyp->previous_output_code_page = GetConsoleOutputCP ();
-      FreeConsole ();
-      AttachConsole (ATTACH_PARENT_PROCESS);
-      HPCON_INTERNAL *hp = (HPCON_INTERNAL *) ttyp->h_pseudo_console;
-      HANDLE tmp = hp->hConHostProcess;
-      ClosePseudoConsole (ttyp->h_pseudo_console);
-      CloseHandle (tmp);
-      ttyp->h_pseudo_console = NULL;
-      ttyp->switch_to_pcon_in = false;
-      ttyp->pcon_pid = 0;
-      ttyp->pcon_start = false;
+      if (ttyp->pcon_pid == myself->pid)
+	{
+	  switch_to = switch_to_stub ?: switch_to;
+	  if (switch_to)
+	    {
+	      /* Change pseudo console owner to another process */
+	      HANDLE new_owner =
+		OpenProcess (PROCESS_DUP_HANDLE, FALSE, switch_to);
+	      HANDLE new_write_pipe = NULL;
+	      HANDLE new_condrv_reference = NULL;
+	      HANDLE new_conhost_process = NULL;
+	      HANDLE new_pcon_in = NULL, new_pcon_out = NULL;
+	      DuplicateHandle (GetCurrentProcess (),
+			       ttyp->h_pcon_write_pipe,
+			       new_owner, &new_write_pipe,
+			       0, TRUE, DUPLICATE_SAME_ACCESS);
+	      DuplicateHandle (GetCurrentProcess (),
+			       ttyp->h_pcon_condrv_reference,
+			       new_owner, &new_condrv_reference,
+			       0, TRUE, DUPLICATE_SAME_ACCESS);
+	      DuplicateHandle (GetCurrentProcess (),
+			       ttyp->h_pcon_conhost_process,
+			       new_owner, &new_conhost_process,
+			       0, TRUE, DUPLICATE_SAME_ACCESS);
+	      DuplicateHandle (GetCurrentProcess (), ttyp->h_pcon_in,
+			       new_owner, &new_pcon_in,
+			       0, TRUE, DUPLICATE_SAME_ACCESS);
+	      DuplicateHandle (GetCurrentProcess (), ttyp->h_pcon_out,
+			       new_owner, &new_pcon_out,
+			       0, TRUE, DUPLICATE_SAME_ACCESS);
+	      CloseHandle (new_owner);
+	      CloseHandle (ttyp->h_pcon_write_pipe);
+	      CloseHandle (ttyp->h_pcon_condrv_reference);
+	      CloseHandle (ttyp->h_pcon_conhost_process);
+	      CloseHandle (ttyp->h_pcon_in);
+	      CloseHandle (ttyp->h_pcon_out);
+	      ttyp->pcon_pid = new_pcon_pid;
+	      ttyp->h_pcon_write_pipe = new_write_pipe;
+	      ttyp->h_pcon_condrv_reference = new_condrv_reference;
+	      ttyp->h_pcon_conhost_process = new_conhost_process;
+	      ttyp->h_pcon_in = new_pcon_in;
+	      ttyp->h_pcon_out = new_pcon_out;
+	    }
+	  else
+	    { /* Close pseudo console */
+	      FreeConsole ();
+	      pinfo p (myself->ppid);
+	      if (p)
+		{
+		  if (!AttachConsole (p->dwProcessId))
+		    AttachConsole (ATTACH_PARENT_PROCESS);
+		}
+	      else
+		AttachConsole (ATTACH_PARENT_PROCESS);
+	      /* Reconstruct pseudo console handler container here for close */
+	      HPCON_INTERNAL *hp =
+		(HPCON_INTERNAL *) HeapAlloc (GetProcessHeap (), 0,
+					      sizeof (*hp));
+	      hp->hWritePipe = ttyp->h_pcon_write_pipe;
+	      hp->hConDrvReference = ttyp->h_pcon_condrv_reference;
+	      hp->hConHostProcess = ttyp->h_pcon_conhost_process;
+	      /* HeapFree() will be called in ClosePseudoConsole() */
+	      ClosePseudoConsole ((HPCON) hp);
+	      CloseHandle (ttyp->h_pcon_conhost_process);
+	      ttyp->pcon_activated = false;
+	      ttyp->switch_to_pcon_in = false;
+	      ttyp->pcon_pid = 0;
+	      ttyp->pcon_start = false;
+	    }
+	}
+      else
+	{
+	  FreeConsole ();
+	  pinfo p (myself->ppid);
+	  if (p)
+	    {
+	      if (!AttachConsole (p->dwProcessId))
+		AttachConsole (ATTACH_PARENT_PROCESS);
+	    }
+	  else
+	    AttachConsole (ATTACH_PARENT_PROCESS);
+	}
+    }
+  else if (ttyp->pcon_pid == myself->pid)
+    {
+      if (switch_to_stub)
+	ttyp->pcon_pid = new_pcon_pid;
+      else
+	{
+	  ttyp->pcon_pid = 0;
+	  ttyp->switch_to_pcon_in = false;
+	}
     }
 }
 
@@ -3222,9 +3420,9 @@ fhandler_pty_slave::term_has_pcon_cap (const WCHAR *env)
 
   /* Check if terminal has CSI6n */
   WaitForSingleObject (input_mutex, INFINITE);
-  /* Set h_pseudo_console and pcon_start so that the response
+  /* Set pcon_activated and pcon_start so that the response
      will sent to io_handle rather than io_handle_cyg. */
-  get_ttyp ()->h_pseudo_console = (HPCON *) -1; /* dummy */
+  get_ttyp ()->pcon_activated = true;
   get_ttyp ()->pcon_pid = myself->pid;
   /* pcon_start will be cleared in master write() when CSI6n is responded. */
   get_ttyp ()->pcon_start = true;
@@ -3255,7 +3453,7 @@ fhandler_pty_slave::term_has_pcon_cap (const WCHAR *env)
 	Sleep (1);
     }
   while (len);
-  get_ttyp ()->h_pseudo_console = NULL;
+  get_ttyp ()->pcon_activated = false;
   get_ttyp ()->pcon_pid = 0;
   if (len == 0)
     goto not_has_csi6n;
@@ -3270,7 +3468,7 @@ not_has_csi6n:
   /* If CSI6n is not responded, pcon_start is not cleared
      in master write(). Therefore, clear it here manually. */
   get_ttyp ()->pcon_start = false;
-  get_ttyp ()->h_pseudo_console = NULL;
+  get_ttyp ()->pcon_activated = false;
   ReleaseMutex (input_mutex);
 maybe_dumb:
   get_ttyp ()->pcon_cap_checked = true;
@@ -3362,7 +3560,7 @@ fhandler_pty_slave::transfer_input (xfer_dir dir, HANDLE from, tty *ttyp,
   if (dir == to_nat)
     {
       cp_from = ttyp->term_code_page;
-      if (ttyp->h_pseudo_console)
+      if (ttyp->pcon_activated)
 	cp_to = CP_UTF8;
       else
 	cp_to = GetConsoleCP ();
@@ -3378,7 +3576,7 @@ fhandler_pty_slave::transfer_input (xfer_dir dir, HANDLE from, tty *ttyp,
 
   bool transfered = false;
 
-  if (dir == to_cyg && ttyp->h_pseudo_console)
+  if (dir == to_cyg && ttyp->pcon_activated)
     { /* from handle is console handle */
       INPUT_RECORD r[INREC_SIZE];
       DWORD n;
@@ -3462,7 +3660,7 @@ fhandler_pty_slave::transfer_input (xfer_dir dir, HANDLE from, tty *ttyp,
 	  DWORD n = MIN (bytes_in_pipe, NT_MAX_PATH);
 	  ReadFile (from, buf, n, &n, NULL);
 	  char *ptr = buf;
-	  if (dir == to_nat && ttyp->h_pseudo_console)
+	  if (dir == to_nat && ttyp->pcon_activated)
 	    {
 	      char *p = buf;
 	      while ((p = (char *) memchr (p, '\n', n - (p - buf))))
diff --git a/winsup/cygwin/select.cc b/winsup/cygwin/select.cc
index 4e7946435..dc75a2dbf 100644
--- a/winsup/cygwin/select.cc
+++ b/winsup/cygwin/select.cc
@@ -1388,7 +1388,7 @@ pty_slave_startup (select_record *me, select_stuff *stuff)
   fhandler_base *fh = (fhandler_base *) me->fh;
   fhandler_pty_slave *ptys = (fhandler_pty_slave *) fh;
   if (me->read_selected)
-    ptys->mask_switch_to_pcon_in (true);
+    ptys->mask_switch_to_pcon_in (true, true);
 
   select_pipe_info *pi = stuff->device_specific_ptys;
   if (pi->start)
@@ -1415,7 +1415,7 @@ pty_slave_cleanup (select_record *me, select_stuff *stuff)
   if (!pi)
     return;
   if (me->read_selected && pi->start)
-    ptys->mask_switch_to_pcon_in (false);
+    ptys->mask_switch_to_pcon_in (false, false);
   if (pi->thread)
     {
       pi->stop_thread = true;
diff --git a/winsup/cygwin/spawn.cc b/winsup/cygwin/spawn.cc
index 383a5a03e..c4b612815 100644
--- a/winsup/cygwin/spawn.cc
+++ b/winsup/cygwin/spawn.cc
@@ -656,6 +656,7 @@ child_info_spawn::worker (const char *prog_arg, const char *const *argv,
       bool enable_pcon = false;
       HANDLE ptys_from_master = NULL;
       HANDLE ptys_input_available_event = NULL;
+      HANDLE ptys_output_mutex = NULL;
       tty *ptys_ttyp = NULL;
       _minor_t ptys_unit = 0;
       if (!iscygwin () && ptys_primary && is_console_app (runpath))
@@ -676,6 +677,9 @@ child_info_spawn::worker (const char *prog_arg, const char *const *argv,
 	  DuplicateHandle (GetCurrentProcess (), ptys_input_available_event,
 			   GetCurrentProcess (), &ptys_input_available_event,
 			   0, 0, DUPLICATE_SAME_ACCESS);
+	  DuplicateHandle (GetCurrentProcess (), ptys_primary->output_mutex,
+			   GetCurrentProcess (), &ptys_output_mutex,
+			   0, 0, DUPLICATE_SAME_ACCESS);
 	  if (!enable_pcon)
 	    fhandler_pty_slave::transfer_input (fhandler_pty_slave::to_nat,
 						ptys_primary->get_handle_cyg (),
@@ -965,16 +969,22 @@ child_info_spawn::worker (const char *prog_arg, const char *const *argv,
 	  if (ptys_ttyp)
 	    {
 	      ptys_ttyp->wait_pcon_fwd ();
-	      fhandler_pty_slave::transfer_input (fhandler_pty_slave::to_cyg,
-						  ptys_from_master,
-						  ptys_ttyp, ptys_unit,
-						  ptys_input_available_event);
+	      /* Do not transfer input if another process using pseudo
+		 console exists. */
+	      WaitForSingleObject (ptys_output_mutex, INFINITE);
+	      if (!fhandler_pty_common::get_console_process_id
+			      (myself->exec_dwProcessId, false, true, true))
+		fhandler_pty_slave::transfer_input (fhandler_pty_slave::to_cyg,
+						    ptys_from_master,
+						    ptys_ttyp, ptys_unit,
+						    ptys_input_available_event);
 	      CloseHandle (ptys_from_master);
 	      CloseHandle (ptys_input_available_event);
+	      fhandler_pty_slave::close_pseudoconsole (ptys_ttyp);
+	      ReleaseMutex (ptys_output_mutex);
+	      CloseHandle (ptys_output_mutex);
 	    }
-	  if (enable_pcon)
-	    fhandler_pty_slave::close_pseudoconsole (ptys_ttyp);
-	  else if (cons_native)
+	  if (cons_native)
 	    {
 	      fhandler_console::request_xterm_mode_output (true,
 							   &cons_handle_set);
@@ -992,16 +1002,22 @@ child_info_spawn::worker (const char *prog_arg, const char *const *argv,
 	  if (ptys_ttyp)
 	    {
 	      ptys_ttyp->wait_pcon_fwd ();
-	      fhandler_pty_slave::transfer_input (fhandler_pty_slave::to_cyg,
-						  ptys_from_master,
-						  ptys_ttyp, ptys_unit,
-						  ptys_input_available_event);
+	      /* Do not transfer input if another process using pseudo
+		 console exists. */
+	      WaitForSingleObject (ptys_output_mutex, INFINITE);
+	      if (!fhandler_pty_common::get_console_process_id
+			      (myself->exec_dwProcessId, false, true, true))
+		fhandler_pty_slave::transfer_input (fhandler_pty_slave::to_cyg,
+						    ptys_from_master,
+						    ptys_ttyp, ptys_unit,
+						    ptys_input_available_event);
 	      CloseHandle (ptys_from_master);
 	      CloseHandle (ptys_input_available_event);
+	      fhandler_pty_slave::close_pseudoconsole (ptys_ttyp);
+	      ReleaseMutex (ptys_output_mutex);
+	      CloseHandle (ptys_output_mutex);
 	    }
-	  if (enable_pcon)
-	    fhandler_pty_slave::close_pseudoconsole (ptys_ttyp);
-	  else if (cons_native)
+	  if (cons_native)
 	    {
 	      fhandler_console::request_xterm_mode_output (true,
 							   &cons_handle_set);
diff --git a/winsup/cygwin/tty.cc b/winsup/cygwin/tty.cc
index e6c0b680e..fb4501c1b 100644
--- a/winsup/cygwin/tty.cc
+++ b/winsup/cygwin/tty.cc
@@ -235,7 +235,7 @@ tty::init ()
   master_pid = 0;
   is_console = false;
   column = 0;
-  h_pseudo_console = NULL;
+  pcon_activated = false;
   switch_to_pcon_in = false;
   pcon_pid = 0;
   term_code_page = 0;
diff --git a/winsup/cygwin/tty.h b/winsup/cygwin/tty.h
index 47be8e4a0..e2e6dfeb6 100644
--- a/winsup/cygwin/tty.h
+++ b/winsup/cygwin/tty.h
@@ -96,13 +96,17 @@ private:
   HANDLE _to_master_cyg;
   HANDLE _to_slave;
   HANDLE _to_slave_cyg;
-  HPCON h_pseudo_console;
+  bool pcon_activated;
   bool pcon_start;
   bool switch_to_pcon_in;
   pid_t pcon_pid;
   UINT term_code_page;
   DWORD pcon_last_time;
   HANDLE h_pcon_write_pipe;
+  HANDLE h_pcon_condrv_reference;
+  HANDLE h_pcon_conhost_process;
+  HANDLE h_pcon_in;
+  HANDLE h_pcon_out;
   bool pcon_cap_checked;
   bool has_csi6n;
   bool need_invisible_console;