[PATCH] Cygwin: console: Fix hangup of less on quit after the window is resized.

[Takashi Yano <takashi.yano@nifty.ne.jp>]

https://cygwin.com/pipermail/cygwin/2022-December/252737.html

If the less is started from non-cygwin shell and window size is
changed, it will hang-up when quitting. The cause of the proglem is
that less uses longjump() in signal handler. If the signal handler
is called while cygwin is acquiring the mutex, cygwin loses the
chance to release mutex. With this patch, the mutex is released
just before calling kill_pgrp() and re-acquired when kill_pgrp()
returns.

Reported-by: Gregory Mason <grmason@epic.com>
Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>
---
 winsup/cygwin/fhandler/console.cc | 4 ++++
 winsup/cygwin/release/3.4.4       | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/winsup/cygwin/fhandler/console.cc b/winsup/cygwin/fhandler/console.cc
index bbf4b0103..ee07c84f8 100644
--- a/winsup/cygwin/fhandler/console.cc
+++ b/winsup/cygwin/fhandler/console.cc
@@ -928,7 +928,11 @@ fhandler_console::send_winch_maybe ()
       if (wincap.has_con_24bit_colors () && !con_is_legacy
 	  && wincap.has_con_broken_tabs ())
 	fix_tab_position (get_output_handle ());
+      /* longjmp() may be called in the signal handler like less,
+	 so release input_mutex temporarily before kill_pgrp(). */
+      release_input_mutex ();
       get_ttyp ()->kill_pgrp (SIGWINCH);
+      acquire_input_mutex (mutex_timeout);
       return true;
     }
   return false;
diff --git a/winsup/cygwin/release/3.4.4 b/winsup/cygwin/release/3.4.4
index 6ac702375..3331b3166 100644
--- a/winsup/cygwin/release/3.4.4
+++ b/winsup/cygwin/release/3.4.4
@@ -3,3 +3,7 @@ Bug Fixes
 
 - Fix an uninitialized variable having weird side-effects in path handling.
   Addresses: https://cygwin.com/pipermail/cygwin/2022-December/252734.html
+
+- Fix hang-up of less on quit which occurs when it is started from non-cygwin
+  shell and window is resized.
+  Addresses: https://cygwin.com/pipermail/cygwin/2022-December/252737.html
-- 
2.39.0