KQueue support for M:N threads

* Allows macOS users to use M:N threads (and technically FreeBSD, though it has not been verified on FreeBSD)

* Include sys/event.h header check for macros, and include sys/event.h when present

* Rename epoll_fd to more generic kq_fd (Kernel event Queue) for use by both epoll and kqueue

* MAP_STACK is not available on macOS so conditionall apply it to mmap flags

* Set fd to close on exec

* Log debug messages specific to kqueue and epoll on creation

* close_invalidate raises an error for the kqueue fd on child process fork. It's unclear rn if that's a bug, or if it's kqueue specific behavior

Use kq with rb_thread_wait_for_single_fd

* Only platforms with `USE_POLL` (linux) had changes applied to take advantage of kernel event queues. It needed to be applied to the `select` so that kqueue could be properly applied

* Clean up kqueue specific code and make sure only flags that were actually set are removed (or an error is raised)

* Also handle kevent specific errnos, since most don't apply from epoll to kqueue

* Use the more platform standard close-on-exec approach of `fcntl` and `FD_CLOEXEC`. The io-event gem uses `ioctl`, but fcntl seems to be the recommended choice. It is also what Go, Bun, and Libuv use

* We're making changes in this file anyways - may as well fix a couple spelling mistakes while here

Make sure FD_CLOEXEC carries over in dup

* Otherwise the kqueue descriptor should have FD_CLOEXEC, but doesn't and fails in assert_close_on_exec

1 files changed, 18 insertions, 6 deletions

diff --git a/thread_pthread.c b/thread_pthread.c
index e7e827793b..d8ca403be6 100644
--- a/thread_pthread.c
+++ b/thread_pthread.c
@@ -62,6 +62,10 @@ static const void *const condattr_monotonic = NULL;
 
 #include COROUTINE_H
 
+#ifndef HAVE_SYS_EVENT_H
+#define HAVE_SYS_EVENT_H 0
+#endif
+
 #ifndef HAVE_SYS_EPOLL_H
 #define HAVE_SYS_EPOLL_H 0
 #else
@@ -78,6 +82,9 @@ static const void *const condattr_monotonic = NULL;
   #elif HAVE_SYS_EPOLL_H
     #include <sys/epoll.h>
     #define USE_MN_THREADS 1
+  #elif HAVE_SYS_EVENT_H
+    #include <sys/event.h>
+    #define USE_MN_THREADS 1
   #else
     #define USE_MN_THREADS 0
   #endif
@@ -2799,10 +2806,15 @@ static struct {
 
     int comm_fds[2]; // r, w
 
+#if (HAVE_SYS_EPOLL_H || HAVE_SYS_EVENT_H) && USE_MN_THREADS
+    int event_fd; // kernel event queue fd (epoll/kqueue)
+#endif
 #if HAVE_SYS_EPOLL_H && USE_MN_THREADS
 #define EPOLL_EVENTS_MAX 0x10
-    int epoll_fd;
     struct epoll_event finished_events[EPOLL_EVENTS_MAX];
+#elif HAVE_SYS_EVENT_H && USE_MN_THREADS
+#define KQUEUE_EVENTS_MAX 0x10
+    struct kevent finished_events[KQUEUE_EVENTS_MAX];
 #endif
 
     // waiting threads list
@@ -3088,7 +3100,7 @@ rb_thread_create_timer_thread(void)
 
             CLOSE_INVALIDATE_PAIR(timer_th.comm_fds);
 #if HAVE_SYS_EPOLL_H && USE_MN_THREADS
-            close_invalidate(&timer_th.epoll_fd, "close epoll_fd");
+            close_invalidate(&timer_th.event_fd, "close event_fd");
 #endif
             rb_native_mutex_destroy(&timer_th.waiting_lock);
         }
@@ -3099,8 +3111,8 @@ rb_thread_create_timer_thread(void)
         // open communication channel
         setup_communication_pipe_internal(timer_th.comm_fds);
 
-        // open epoll fd
-        timer_thread_setup_nm();
+        // open event fd
+        timer_thread_setup_mn();
     }
 
     pthread_create(&timer_th.pthread_id, NULL, timer_thread_func, GET_VM());
@@ -3181,8 +3193,8 @@ rb_reserved_fd_p(int fd)
 
     if (fd == timer_th.comm_fds[0] ||
         fd == timer_th.comm_fds[1]
-#if HAVE_SYS_EPOLL_H && USE_MN_THREADS
-        || fd == timer_th.epoll_fd
+#if (HAVE_SYS_EPOLL_H || HAVE_SYS_EVENT_H) && USE_MN_THREADS
+        || fd == timer_th.event_fd
 #endif
         ) {
         goto check_fork_gen;