Implement uv_sanitize_signal_handling().

include/uv.h

@@ -2251,6 +2251,30 @@ UV_EXTERN extern uint64_t uv_hrtime(void);
  */
 UV_EXTERN void uv_disable_stdio_inheritance(void);
 
+/*
+ * On Unix, this function can be called early from main, before any threads
+ * are started, to set up a safe environment with respect to signal handling.
+ * 
+ * This function does the following when it is called for the first time:
+ * - Starts a dummy thread, which consists of an infinite pause() loop.
+ * - Blocks all signals in the current thread.
+ * 
+ * Remember that signal masks are thread-specific and inherited at thread
+ * creation. Therefore the dummy thread will have the same signals unblocked
+ * as the main thread did when this function was called.
+ * 
+ * This will ensure that signals directed at the process will only be processed
+ * by this dummy thread. Most imporantly, system calls will not randomly fail
+ * with EINTR errors (unless signals are later unmasked by threads...).
+ * 
+ * Calling this function is not necessary for libuv itself to operate
+ * correctly, since EINTR is handled by retrying calls. But code outside
+ * of libuv may not be handling EINTR.
+ * 
+ * This function does nothing on Windows.
+ */
+UV_EXTERN void uv_sanitize_signal_handling(void);
+
 /*
  * Opens a shared library. The filename is in utf-8. Returns 0 on success and
  * -1 on error. Call uv_dlerror(uv_lib_t*) to get the error message.

src/unix/core.c

@@ -75,6 +75,10 @@
 #endif
 
 static void uv__run_pending(uv_loop_t* loop);
+static void uv__signal_thread_proc(void *arg);
+
+static int uv__sanitize_signals_done;
+static uv_thread_t uv__signal_thread;
 
 /* Verify that uv_buf_t is ABI-compatible with struct iovec. */
 STATIC_ASSERT(sizeof(uv_buf_t) == sizeof(struct iovec));
@@ -662,6 +666,29 @@ void uv_disable_stdio_inheritance(void) {
 }
 
 
+void uv_sanitize_signal_handling(void) {
+  sigset_t full_ss;
+  sigset_t old_ss;
+
+  /* Don't do it twice.
+   * This looks like a race condition but then it should only be
+   * called from main. */
+  if (uv__sanitize_signals_done) {
+    return;
+  }
+  uv__sanitize_signals_done = 1;
+
+  // Create dummy signal handling thread.
+  if (uv_thread_create(&uv__signal_thread, uv__signal_thread_proc, NULL))
+    abort();
+
+  /* Block all signals in the current (main) thread. */
+  sigfillset(&full_ss);
+  if (pthread_sigmask(SIG_SETMASK, &full_ss, &old_ss))
+    abort();
+}
+
+
 static void uv__run_pending(uv_loop_t* loop) {
   QUEUE* q;
   uv__io_t* w;
@@ -946,3 +973,11 @@ int uv__dup2_cloexec(int oldfd, int newfd) {
     return r;
   }
 }
+
+
+static void uv__signal_thread_proc(void* arg) {
+  /* Handle signals by doing nothing. */
+  while (1) {
+      pause();
+  }
+}

src/win/core.c

@@ -456,3 +456,6 @@ int uv__socket_sockopt(uv_handle_t* handle, int optname, int* value) {
 
   return 0;
 }
+
+void uv_sanitize_signal_handling(void) {
+}