[PATCH 0/2] Make terminal read() thread-safe.

[PATCH 0/2] Make terminal read() thread-safe.

[Takashi Yano]

Currently read() for console and pty slave are somehow
not thread-safe. These patches fix the issue.

Takashi Yano (2):
  Cygwin: console: Make read() thread-safe.
  Cygwin: pty: Make slave read() thread-safe.

 winsup/cygwin/fhandler_console.cc | 7 +++----
 winsup/cygwin/fhandler_tty.cc     | 6 ++++++
 winsup/cygwin/select.cc           | 3 ---
 3 files changed, 9 insertions(+), 7 deletions(-)

-- 
2.30.0

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

[Takashi Yano]

- Currently read() is somehow not thread-safe. This patch fixes the
  issue.
---
 winsup/cygwin/fhandler_console.cc | 7 +++----
 winsup/cygwin/select.cc           | 3 ---
 2 files changed, 3 insertions(+), 7 deletions(-)

diff --git a/winsup/cygwin/fhandler_console.cc b/winsup/cygwin/fhandler_console.cc
index 02d0ac052..8324faaa2 100644
--- a/winsup/cygwin/fhandler_console.cc
+++ b/winsup/cygwin/fhandler_console.cc
@@ -572,9 +572,7 @@ wait_retry:
 
       int ret;
       acquire_attach_mutex (INFINITE);
-      acquire_input_mutex (INFINITE);
       ret = process_input_message ();
-      release_input_mutex ();
       release_attach_mutex ();
       switch (ret)
 	{
@@ -632,6 +630,7 @@ fhandler_console::process_input_message (void)
   if (!shared_console_info)
     return input_error;
 
+  acquire_input_mutex (INFINITE);
   termios *ti = &(get_ttyp ()->ti);
 
   fhandler_console::input_states stat = input_processing;
@@ -641,6 +640,7 @@ fhandler_console::process_input_message (void)
   if (!PeekConsoleInputW (get_handle (), input_rec, INREC_SIZE, &total_read))
     {
       termios_printf ("PeekConsoleInput failed, %E");
+      release_input_mutex ();
       return input_error;
     }
 
@@ -984,9 +984,7 @@ 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;
@@ -1007,6 +1005,7 @@ out:
   DWORD discard_len = min (total_read, i + 1);
   if (discard_len)
     ReadConsoleInputW (get_handle (), input_rec, discard_len, &dummy);
+  release_input_mutex ();
   return stat;
 }
 
diff --git a/winsup/cygwin/select.cc b/winsup/cygwin/select.cc
index dc75a2dbf..a4f401403 100644
--- a/winsup/cygwin/select.cc
+++ b/winsup/cygwin/select.cc
@@ -1083,17 +1083,14 @@ peek_console (select_record *me, bool)
 	}
       else if (!PeekConsoleInputW (h, &irec, 1, &events_read) || !events_read)
 	break;
-      fh->acquire_input_mutex (INFINITE);
       if (fhandler_console::input_winch == fh->process_input_message ()
 	  && global_sigs[SIGWINCH].sa_handler != SIG_IGN
 	  && global_sigs[SIGWINCH].sa_handler != SIG_DFL)
 	{
 	  set_sig_errno (EINTR);
-	  fh->release_input_mutex ();
 	  release_attach_mutex ();
 	  return -1;
 	}
-      fh->release_input_mutex ();
     }
   release_attach_mutex ();
   if (fh->input_ready || fh->get_cons_readahead_valid ())
-- 
2.30.0

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

[Takashi Yano]

On Thu, 28 Jan 2021 20:14:08 +0900
Takashi Yano wrote:
> - Currently read() is somehow not thread-safe. This patch fixes the
>   issue.
> ---
>  winsup/cygwin/fhandler_console.cc | 7 +++----
>  winsup/cygwin/select.cc           | 3 ---
>  2 files changed, 3 insertions(+), 7 deletions(-)

Sorry, this does not seem to be enough. Please wait a while.

-- 
Takashi Yano <takashi.yano@nifty.ne.jp>

[PATCH 2/2] Cygwin: pty: Make slave read() thread-safe.

[Takashi Yano]

- Currently slave read() is somehow not thread-safe. This patch
  fixes the issue.
---
 winsup/cygwin/fhandler_tty.cc | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/winsup/cygwin/fhandler_tty.cc b/winsup/cygwin/fhandler_tty.cc
index 06fc19ac2..48b89ae77 100644
--- a/winsup/cygwin/fhandler_tty.cc
+++ b/winsup/cygwin/fhandler_tty.cc
@@ -1241,6 +1241,7 @@ fhandler_pty_slave::read (void *ptr, size_t& len)
 	time_to_wait = !vtime ? INFINITE : 100 * vtime;
     }
 
+wait_retry:
   while (len)
     {
       switch (cygwait (input_available_event, time_to_wait))
@@ -1319,6 +1320,11 @@ fhandler_pty_slave::read (void *ptr, size_t& len)
 	    }
 	  goto out;
 	}
+      if (!IsEventSignalled (input_available_event))
+	{ /* Maybe another thread has processed input. */
+	  ReleaseMutex (input_mutex);
+	  goto wait_retry;
+	}
 
       if (!bytes_available (bytes_in_pipe))
 	{
-- 
2.30.0