[PATCH v3 1/2] Cygwin: console: Make read() thread-safe.

[Takashi Yano via Cygwin-patches]

- Currently read() is somehow not thread-safe. This patch fixes
  the issue.
---
 winsup/cygwin/fhandler.h          | 10 ++++++++++
 winsup/cygwin/fhandler_console.cc | 11 ++++++-----
 winsup/cygwin/fhandler_termios.cc |  2 ++
 3 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/winsup/cygwin/fhandler.h b/winsup/cygwin/fhandler.h
index a4c1a3816..2fad7d33c 100644
--- a/winsup/cygwin/fhandler.h
+++ b/winsup/cygwin/fhandler.h
@@ -1905,6 +1905,8 @@ class fhandler_termios: public fhandler_base
   tty_min *_tc;
   tty *get_ttyp () {return (tty *) tc ();}
   int eat_readahead (int n);
+  virtual void acquire_input_mutex_if_necessary (DWORD ms) {};
+  virtual void release_input_mutex_if_necessary (void) {};
 
  public:
   tty_min*& tc () {return _tc;}
@@ -2212,6 +2214,14 @@ private:
   void __release_input_mutex (const char *fn, int ln);
   DWORD __acquire_output_mutex (const char *fn, int ln, DWORD ms);
   void __release_output_mutex (const char *fn, int ln);
+  void acquire_input_mutex_if_necessary (DWORD ms)
+  {
+    acquire_input_mutex (ms);
+  }
+  void release_input_mutex_if_necessary (void)
+  {
+    release_input_mutex ();
+  }
 
   char *&rabuf ();
   size_t &ralen ();
diff --git a/winsup/cygwin/fhandler_console.cc 
b/winsup/cygwin/fhandler_console.cc
index 02d0ac052..0b404411e 100644
--- a/winsup/cygwin/fhandler_console.cc
+++ b/winsup/cygwin/fhandler_console.cc
@@ -571,31 +571,34 @@ wait_retry:
 #define buf ((char *) pv)
 
       int ret;
-      acquire_attach_mutex (INFINITE);
       acquire_input_mutex (INFINITE);
+      acquire_attach_mutex (INFINITE);
       ret = process_input_message ();
-      release_input_mutex ();
       release_attach_mutex ();
       switch (ret)
        {
        case input_error:
+         release_input_mutex ();
          goto err;
        case input_processing:
+         release_input_mutex ();
          continue;
        case input_ok: /* input ready */
          break;
        case input_signalled: /* signalled */
+         release_input_mutex ();
          goto sig_exit;
        case input_winch:
+         release_input_mutex ();
          continue;
        default:
          /* Should not come here */
+         release_input_mutex ();
          goto err;
        }
     }
 
   /* Check console read-ahead buffer filled from terminal requests */
-  acquire_input_mutex (INFINITE);
   while (con.cons_rapoi && *con.cons_rapoi && buflen)
     {
       buf[copied_chars++] = *con.cons_rapoi++;
@@ -984,9 +987,7 @@ fhandler_console::process_input_message (void)
       if (toadd)
        {
          ssize_t ret;
-         release_input_mutex ();
          line_edit_status res = line_edit (toadd, nread, *ti, &ret);
-         acquire_input_mutex (INFINITE);
          if (res == line_edit_signalled)
            {
              stat = input_signalled;
diff --git a/winsup/cygwin/fhandler_termios.cc 
b/winsup/cygwin/fhandler_termios.cc
index 36bc6255f..9fbace95c 100644
--- a/winsup/cygwin/fhandler_termios.cc
+++ b/winsup/cygwin/fhandler_termios.cc
@@ -332,7 +332,9 @@ fhandler_termios::line_edit (const char *rptr, size_t 
nread, termios& ti,
 
          termios_printf ("got interrupt %d, sending signal %d", c, sig);
          eat_readahead (-1);
+         release_input_mutex_if_necessary ();
          tc ()->kill_pgrp (sig);
+         acquire_input_mutex_if_necessary (INFINITE);
          ti.c_lflag &= ~FLUSHO;
          sawsig = true;
          goto restart_output;
-- 
2.30.0