[PATCH v7 3/7] Cygwin: console: Use input_mutex in the parent PTY in master thread

[Takashi Yano]

If the console is originating from pseudo console, the input into
console is comming from PTY master. Therefore, input_mutex in PTY
can be used to avoid conflicts between fhandler_pty_master::write()
and cons_master_thread(). With this patch, use parent input_mutex
as well as input_mutex in console device in cons_master_thread().

Fixes: 04f386e9af99 ("Cygwin: console: Inherit pcon hand over from parent pty")
Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>
Reviewed-by:
---
 winsup/cygwin/fhandler/console.cc | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/winsup/cygwin/fhandler/console.cc b/winsup/cygwin/fhandler/console.cc
index 9678775d1..29cdba0d3 100644
--- a/winsup/cygwin/fhandler/console.cc
+++ b/winsup/cygwin/fhandler/console.cc
@@ -63,6 +63,7 @@ fhandler_console::console_state NO_COPY
 static bool NO_COPY inside_pcon_checked = false;
 static bool NO_COPY inside_pcon = false;
 static int NO_COPY parent_pty;
+static HANDLE NO_COPY parent_pty_input_mutex = NULL;
 
 bool NO_COPY fhandler_console::invisible_console;
 
@@ -464,6 +465,8 @@ fhandler_console::cons_master_thread (handle_set_t *p, tty *ttyp)
 	  continue;
 	}
       total_read = 0;
+      if (inside_pcon)
+	WaitForSingleObject (parent_pty_input_mutex, mutex_timeout);
       switch (cygwait (p->input_handle, (DWORD) 0))
 	{
 	case WAIT_OBJECT_0:
@@ -488,6 +491,8 @@ fhandler_console::cons_master_thread (handle_set_t *p, tty *ttyp)
 	default: /* Error */
 	  free (input_rec);
 	  free (input_tmp);
+	  if (inside_pcon)
+	    ReleaseMutex (parent_pty_input_mutex);
 	  ReleaseMutex (p->input_mutex);
 	  return;
 	}
@@ -665,6 +670,8 @@ remove_record:
 	  while (true);
 	}
 skip_writeback:
+      if (inside_pcon)
+	ReleaseMutex (parent_pty_input_mutex);
       ReleaseMutex (p->input_mutex);
       cygwait (40);
     }
@@ -1970,6 +1977,8 @@ fhandler_console::setup_pcon_hand_over ()
 	    inside_pcon = true;
 	    atexit (fhandler_console::pcon_hand_over_proc);
 	    parent_pty = i;
+	    parent_pty_input_mutex =
+	      cygwin_shared->tty[i]->open_input_mutex (MAXIMUM_ALLOWED);
 	    break;
 	  }
       }
@@ -1997,6 +2006,7 @@ fhandler_console::pcon_hand_over_proc (void)
     }
   else
     system_printf("Acquiring pcon_ho_mutex failed.");
+  CloseHandle (parent_pty_input_mutex);
   /* Do not release the mutex.
      Hold onto the mutex until this process completes. */
 }
-- 
2.51.0