Fix lock failures in xg_select

* src/xgselect.c (release_select_lock, acquire_select_lock):
Introduce.
(xg_select): Use `acquire_select_lock', `release_select_lock'.
* src/thread.c (release_select_lock): Introduce for non-GLib builds.
(really_call_select): Call `release_select_lock'.  Simplify by
ensuring acquisition of the lock always succeeds (bug#36609).

1 files changed, 8 insertions, 0 deletions

diff --git a/src/thread.c b/src/thread.c
index b638dd77f8b..b4d8a53cf68 100644
--- a/src/thread.c
+++ b/src/thread.c
@@ -28,6 +28,12 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 #include "pdumper.h"
 #include "keyboard.h"
 
+#ifdef HAVE_GLIB
+#include <xgselect.h>
+#else
+#define release_select_lock() do { } while (0)
+#endif
+
 union aligned_thread_state
 {
   struct thread_state s;
@@ -586,6 +592,8 @@ really_call_select (void *arg)
   sa->result = (sa->func) (sa->max_fds, sa->rfds, sa->wfds, sa->efds,
                            sa->timeout, sa->sigmask);
 
+  release_select_lock ();
+
   block_interrupt_signal (&oldset);
   /* If we were interrupted by C-g while inside sa->func above, the
      signal handler could have called maybe_reacquire_global_lock, in