Avoid crashes on C-g when several threads wait for input

* src/thread.h (m_getcjmp): New member of 'struct thread_state'.
(getcjmp): Define to current thread's 'm_getcjmp'.
* src/thread.c (maybe_reacquire_global_lock): Switch to main
thread, since this is called from a SIGINT handler, which always
runs in the context of the main thread.
* src/lisp.h (sys_jmp_buf, sys_setjmp, sys_longjmp): Move the
definitions before thread.h is included, as thread.h now uses
sys_jmp_buf.
* src/keyboard.c (getcjmp): Remove declaration.
(read_char): Don't call maybe_reacquire_global_lock here.
(handle_interrupt): Call maybe_reacquire_global_lock here, if
invoked from the SIGINT handler, to make sure
quit_throw_to_read_char runs with main thread's Lisp bindings and
uses the main thread's jmp_buf buffer.  (Bug#28630)

1 files changed, 7 insertions, 7 deletions

diff --git a/src/keyboard.c b/src/keyboard.c
index e8701b88708..ee353d2b078 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -145,10 +145,6 @@ static Lisp_Object recover_top_level_message;
 /* Message normally displayed by Vtop_level.  */
 static Lisp_Object regular_top_level_message;
 
-/* For longjmp to where kbd input is being done.  */
-
-static sys_jmp_buf getcjmp;
-
 /* True while displaying for echoing.   Delays C-g throwing.  */
 
 static bool echoing;
@@ -2570,9 +2566,6 @@ read_char (int commandflag, Lisp_Object map,
          so restore it now.  */
       restore_getcjmp (save_jump);
       pthread_sigmask (SIG_SETMASK, &empty_mask, 0);
-#if THREADS_ENABLED
-      maybe_reacquire_global_lock ();
-#endif
       unbind_to (jmpcount, Qnil);
       XSETINT (c, quit_char);
       internal_last_event_frame = selected_frame;
@@ -10508,6 +10501,13 @@ handle_interrupt (bool in_signal_handler)
          outside of polling since we don't get SIGIO like X and we don't have a
          separate event loop thread like W32.  */
 #ifndef HAVE_NS
+#ifdef THREADS_ENABLED
+  /* If we were called from a signal handler, we must be in the main
+     thread, see deliver_process_signal.  So we must make sure the
+     main thread holds the global lock.  */
+  if (in_signal_handler)
+    maybe_reacquire_global_lock ();
+#endif
   if (waiting_for_input && !echoing)
     quit_throw_to_read_char (in_signal_handler);
 #endif