mach: use signal kqueue instead of sigwait (JuliaLang#22041)

this may help avoid getting spurious sigwait notifications

src/signals-unix.c

@@ -22,12 +22,18 @@
 // Figure out the best signals/timers to use for this platform
 #ifdef __APPLE__ // Darwin's mach ports allow signal-free thread management
 #define HAVE_MACH
+#define HAVE_KEVENT
 #elif defined(__FreeBSD__) // generic bsd
 #define HAVE_ITIMER
+#define HAVE_KEVENT
 #else // generic linux
 #define HAVE_TIMER
 #endif
 
+#ifdef HAVE_KEVENT
+#include <sys/event.h>
+#endif
+
 // 8M signal stack, same as default stack size and enough
 // for reasonable finalizers.
 // Should also be enough for parallel GC when we have it =)
@@ -174,7 +180,7 @@ static int is_addr_on_stack(jl_ptls_t ptls, void *addr)
 #endif
 }
 
-void sigdie_handler(int sig, siginfo_t *info, void *context)
+static void sigdie_handler(int sig, siginfo_t *info, void *context)
 {
  jl_ptls_t ptls = jl_get_ptls_states();
  sigset_t sset;
@@ -511,7 +517,7 @@ void jl_install_thread_signal_handler(jl_ptls_t ptls)
  ptls->signal_stack = signal_stack;
 }
 
-void jl_sigsetset(sigset_t *sset)
+static void jl_sigsetset(sigset_t *sset)
 {
  sigemptyset(sset);
  sigaddset(sset, SIGINT);
@@ -528,21 +534,76 @@ void jl_sigsetset(sigset_t *sset)
 #endif
 }
 
+#ifdef HAVE_KEVENT
+static void kqueue_signal(int *sigqueue, struct kevent *ev, int sig)
+{
+ if (*sigqueue == -1)
+ return;
+ EV_SET(ev, sig, EVFILT_SIGNAL, EV_ADD, 0, 0, 0);
+ if (kevent(*sigqueue, ev, 1, NULL, 0, NULL)) {
+ perror("signal kevent");
+ close(*sigqueue);
+ *sigqueue = -1;
+ }
+ else {
+ signal(sig, SIG_IGN);
+ }
+}
+#endif
+
 static void *signal_listener(void *arg)
 {
  static uintptr_t bt_data[JL_MAX_BT_SIZE + 1];
  static size_t bt_size = 0;
  sigset_t sset;
  int sig, critical, profile;
  jl_sigsetset(&sset);
+#ifdef HAVE_KEVENT
+ struct kevent ev;
+ int sigqueue = kqueue();
+ if (sigqueue == -1) {
+ perror("signal kqueue");
+ }
+ else {
+ kqueue_signal(&sigqueue, &ev, SIGINT);
+ kqueue_signal(&sigqueue, &ev, SIGTERM);
+ kqueue_signal(&sigqueue, &ev, SIGABRT);
+ kqueue_signal(&sigqueue, &ev, SIGQUIT);
+#ifdef SIGINFO
+ kqueue_signal(&sigqueue, &ev, SIGINFO);
+#else
+ kqueue_signal(&sigqueue, &ev, SIGUSR1);
+#endif
+#ifdef HAVE_ITIMER
+ kqueue_signal(&sigqueue, &ev, SIGPROF);
+#endif
+ }
+#endif
  while (1) {
  profile = 0;
  sig = 0;
  errno = 0;
+#ifdef HAVE_KEVENT
+ if (sigqueue != -1) {
+ int nevents = kevent(sigqueue, NULL, 0, &ev, 1, NULL);
+ if (nevents == -1) {
+ if (errno == EINTR)
+ continue;
+ perror("signal kevent");
+ }
+ if (nevents != 1) {
+ close(sigqueue);
+ sigqueue = -1;
+ continue;
+ }
+ sig = ev.ident;
+ }
+ else
+#endif
  if (sigwait(&sset, &sig)) {
  sig = SIGABRT; // this branch can't occur, unless we had stack memory corruption of sset
  }
- if (!sig || errno == EINTR) {
+ else if (!sig || errno == EINTR) {
  // This should never happen, but it has been observed to occur
  // when this thread gets used to handle run a signal handler (without SA_RESTART).
  // It would be nice to prohibit the kernel from doing that, by blocking signals on this thread,
@@ -668,15 +729,15 @@ void restore_signals(void)
  }
 }
 
-void fpe_handler(int sig, siginfo_t *info, void *context)
+static void fpe_handler(int sig, siginfo_t *info, void *context)
 {
  (void)info;
  jl_ptls_t ptls = jl_get_ptls_states();
  jl_unblock_signal(sig);
  jl_throw_in_ctx(ptls, jl_diverror_exception, context);
 }
 
-void sigint_handler(int sig)
+static void sigint_handler(int sig)
 {
  jl_sigint_passed = 1;
 }