Speed up GetRandomBytes by only entering signal-blocking scope once.

runtime/bin/eventhandler_macos.cc

Index: runtime/bin/eventhandler_macos.cc
diff --git a/runtime/bin/eventhandler_macos.cc b/runtime/bin/eventhandler_macos.cc
index beeae4b50f5bb4240a903b577b52a298fc8b7fdd..eb01d188d3d9d122da45feac0b701d3829d9f8ad 100644
--- a/runtime/bin/eventhandler_macos.cc
+++ b/runtime/bin/eventhandler_macos.cc
@@ -179,7 +179,7 @@ void EventHandlerImplementation::WakeupHandler(intptr_t id,
 void EventHandlerImplementation::HandleInterruptFd() {
   const intptr_t MAX_MESSAGES = kInterruptMessageSize;
   InterruptMessage msg[MAX_MESSAGES];
-  ssize_t bytes = TEMP_FAILURE_RETRY(
+  ssize_t bytes = TEMP_FAILURE_RETRY_NO_SIGNAL_BLOCKER(
       read(interrupt_fds_[0], msg, MAX_MESSAGES * kInterruptMessageSize));
   for (ssize_t i = 0; i < bytes / kInterruptMessageSize; i++) {
     if (msg[i].id == kTimerId) {
@@ -348,6 +348,7 @@ void EventHandlerImplementation::HandleTimeout() {
 
 
 void EventHandlerImplementation::EventHandlerEntry(uword args) {
+  ThreadSignalBlocker signal_blocker(SIGPROF);
   static const intptr_t kMaxEvents = 16;
   struct kevent events[kMaxEvents];
   EventHandler* handler = reinterpret_cast<EventHandler*>(args);
@@ -368,12 +369,8 @@ void EventHandlerImplementation::EventHandlerEntry(uword args) {
       ts.tv_nsec = (millis32 - (secs * 1000)) * 1000000;
       timeout = &ts;
     }
-    intptr_t result = TEMP_FAILURE_RETRY(kevent(handler_impl->kqueue_fd_,
-                                                NULL,
-                                                0,
-                                                events,
-                                                kMaxEvents,
-                                                timeout));
+    intptr_t result = TEMP_FAILURE_RETRY_NO_SIGNAL_BLOCKER(
+        kevent(handler_impl->kqueue_fd_, NULL, 0, events, kMaxEvents, timeout));
     if (result == -1) {
       const int kBufferSize = 1024;
       char error_message[kBufferSize];