epoll: Suggest not-so-UUOC if epoll_ctl() fails for stdin

diff --git a/src/lib/ioloop-epoll.c b/src/lib/ioloop-epoll.c
index f22bafee92851ea758f6f99dc8681d81c7e51cd8..5f7095b7dcdcbf7a4f52b7d4feb7278d25dce6b2 100644 (file)
--- a/src/lib/ioloop-epoll.c
+++ b/src/lib/ioloop-epoll.c
@@ -112,7 +112,9 @@ void io_loop_handle_add(struct io_file *io)
        if (epoll_ctl(ctx->epfd, op, io->fd, &event) < 0) {
                if (errno == EPERM && op == EPOLL_CTL_ADD) {
                        i_fatal("epoll_ctl(add, %d) failed: %m "
-                               "(fd doesn't support epoll)", io->fd);
+                               "(fd doesn't support epoll%s)", io->fd,
+                               io->fd != STDIN_FILENO ? "" :
+                               " - instead of '<file', try 'cat file|'");
                }
                i_panic("epoll_ctl(%s, %d) failed: %m",
                        op == EPOLL_CTL_ADD ? "add" : "mod", io->fd);