unix: don't retry close() on EINTR

Linux 2.6 always closes the file descriptor, even on EINTR. Retrying the close()
call isn't merely useless, it's actively harmful - the file descriptor may have
been acquired by another thread.

src/unix/core.c

@@ -790,23 +790,6 @@ int uv__accept(int sockfd, struct sockaddr* saddr, socklen_t slen) {
 }
 
 
-int uv__close(int fd) {
-  int status;
-
-  /*
-   * Retry on EINTR. You may think this is academic but on linux
-   * and probably other Unices too, close(2) is interruptible.
-   * Failing to handle EINTR is a common source of fd leaks.
-   */
-  do {
-    status = close(fd);
-  }
-  while (status == -1 && errno == EINTR);
-
-  return status;
-}
-
-
 int uv__nonblock(int fd, int set) {
 #if FIONBIO
   return ioctl(fd, FIONBIO, &set);

src/unix/internal.h

@@ -154,14 +154,19 @@ enum {
   UV_TCP_KEEPALIVE = 0x100   /* Turn on keep-alive. */
 };
 
-int uv__close(int fd);
+/* core */
 void uv__handle_init(uv_loop_t* loop, uv_handle_t* handle, uv_handle_type type);
-
-
 int uv__nonblock(int fd, int set) __attribute__((unused));
 int uv__cloexec(int fd, int set) __attribute__((unused));
 int uv__socket(int domain, int type, int protocol);
 
+/* We used to handle EINTR in uv__close() but linux 2.6 will have closed the
+ * file descriptor anyway, even on EINTR. Retrying in that case isn't merely
+ * useless, it's actively harmful - the file descriptor may have been acquired
+ * by another thread.
+ */
+#define uv__close(fd) close(fd)
+
 /* error */
 uv_err_code uv_translate_sys_error(int sys_errno);
 void uv_fatal_error(const int errorno, const char* syscall);