diff --git a/ext/-test-/wait_for_single_fd/depend b/ext/-test-/wait_for_single_fd/depend
deleted file mode 100644
index 2f943245f7..0000000000
--- a/ext/-test-/wait_for_single_fd/depend
+++ /dev/null
@@ -1,165 +0,0 @@
-# AUTOGENERATED DEPENDENCIES START
-wait_for_single_fd.o: $(RUBY_EXTCONF_H)
-wait_for_single_fd.o: $(arch_hdrdir)/ruby/config.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/anyargs.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/arithmetic.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/arithmetic/char.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/arithmetic/double.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/arithmetic/fixnum.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/arithmetic/gid_t.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/arithmetic/int.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/arithmetic/intptr_t.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/arithmetic/long.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/arithmetic/long_long.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/arithmetic/mode_t.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/arithmetic/off_t.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/arithmetic/pid_t.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/arithmetic/short.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/arithmetic/size_t.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/arithmetic/st_data_t.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/arithmetic/uid_t.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/assume.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/attr/alloc_size.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/attr/artificial.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/attr/cold.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/attr/const.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/attr/constexpr.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/attr/deprecated.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/attr/diagnose_if.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/attr/enum_extensibility.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/attr/error.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/attr/flag_enum.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/attr/forceinline.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/attr/format.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/attr/maybe_unused.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/attr/noalias.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/attr/nodiscard.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/attr/noexcept.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/attr/noinline.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/attr/nonnull.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/attr/noreturn.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/attr/pure.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/attr/restrict.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/attr/returns_nonnull.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/attr/warning.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/attr/weakref.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/cast.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/compiler_is.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/compiler_is/apple.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/compiler_is/clang.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/compiler_is/gcc.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/compiler_is/intel.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/compiler_is/msvc.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/compiler_is/sunpro.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/compiler_since.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/config.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/constant_p.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/core.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/core/rarray.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/core/rbasic.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/core/rbignum.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/core/rclass.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/core/rdata.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/core/rfile.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/core/rhash.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/core/robject.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/core/rregexp.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/core/rstring.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/core/rstruct.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/core/rtypeddata.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/ctype.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/dllexport.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/dosish.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/error.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/eval.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/event.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/fl_type.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/gc.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/glob.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/globals.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/has/attribute.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/has/builtin.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/has/c_attribute.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/has/cpp_attribute.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/has/declspec_attribute.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/has/extension.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/has/feature.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/has/warning.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/array.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/bignum.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/class.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/compar.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/complex.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/cont.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/dir.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/enum.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/enumerator.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/error.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/eval.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/file.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/gc.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/hash.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/io.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/load.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/marshal.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/numeric.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/object.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/parse.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/proc.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/process.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/random.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/range.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/rational.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/re.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/ruby.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/select.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/select/largesize.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/signal.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/sprintf.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/string.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/struct.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/thread.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/time.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/variable.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/intern/vm.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/interpreter.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/iterator.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/memory.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/method.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/module.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/newobj.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/rgengc.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/scan_args.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/special_consts.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/static_assert.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/stdalign.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/stdbool.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/symbol.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/value.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/value_type.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/variable.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/warning_push.h
-wait_for_single_fd.o: $(hdrdir)/ruby/internal/xmalloc.h
-wait_for_single_fd.o: $(hdrdir)/ruby/assert.h
-wait_for_single_fd.o: $(hdrdir)/ruby/backward.h
-wait_for_single_fd.o: $(hdrdir)/ruby/backward/2/assume.h
-wait_for_single_fd.o: $(hdrdir)/ruby/backward/2/attributes.h
-wait_for_single_fd.o: $(hdrdir)/ruby/backward/2/bool.h
-wait_for_single_fd.o: $(hdrdir)/ruby/backward/2/gcc_version_since.h
-wait_for_single_fd.o: $(hdrdir)/ruby/backward/2/inttypes.h
-wait_for_single_fd.o: $(hdrdir)/ruby/backward/2/limits.h
-wait_for_single_fd.o: $(hdrdir)/ruby/backward/2/long_long.h
-wait_for_single_fd.o: $(hdrdir)/ruby/backward/2/stdalign.h
-wait_for_single_fd.o: $(hdrdir)/ruby/backward/2/stdarg.h
-wait_for_single_fd.o: $(hdrdir)/ruby/defines.h
-wait_for_single_fd.o: $(hdrdir)/ruby/encoding.h
-wait_for_single_fd.o: $(hdrdir)/ruby/intern.h
-wait_for_single_fd.o: $(hdrdir)/ruby/io.h
-wait_for_single_fd.o: $(hdrdir)/ruby/missing.h
-wait_for_single_fd.o: $(hdrdir)/ruby/onigmo.h
-wait_for_single_fd.o: $(hdrdir)/ruby/oniguruma.h
-wait_for_single_fd.o: $(hdrdir)/ruby/ruby.h
-wait_for_single_fd.o: $(hdrdir)/ruby/st.h
-wait_for_single_fd.o: $(hdrdir)/ruby/subst.h
-wait_for_single_fd.o: wait_for_single_fd.c
-# AUTOGENERATED DEPENDENCIES END
diff --git a/ext/-test-/wait_for_single_fd/extconf.rb b/ext/-test-/wait_for_single_fd/extconf.rb
deleted file mode 100644
index c27100fb42..0000000000
--- a/ext/-test-/wait_for_single_fd/extconf.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-# frozen_string_literal: false
-case RUBY_PLATFORM when /mingw/ then
-  # skip
-else
-  headers = %w(sys/types.h sys/time.h sys/event.h).select { |h| have_header(h) }
-  have_func('kqueue', headers)
-end
-create_makefile("-test-/wait_for_single_fd")
diff --git a/ext/-test-/wait_for_single_fd/wait_for_single_fd.c b/ext/-test-/wait_for_single_fd/wait_for_single_fd.c
deleted file mode 100644
index b8a33979bc..0000000000
--- a/ext/-test-/wait_for_single_fd/wait_for_single_fd.c
+++ /dev/null
@@ -1,94 +0,0 @@
-#include "ruby/ruby.h"
-#include "ruby/io.h"
-
-static VALUE
-wait_for_single_fd(VALUE ign, VALUE fd, VALUE events, VALUE timeout)
-{
-    struct timeval tv;
-    struct timeval *tvp = NULL;
-    int rc;
-
-    if (!NIL_P(timeout)) {
-	tv = rb_time_timeval(timeout);
-	tvp = &tv;
-    }
-
-    rc = rb_wait_for_single_fd(NUM2INT(fd), NUM2INT(events), tvp);
-    if (rc == -1)
-	rb_sys_fail("rb_wait_for_single_fd");
-    return INT2NUM(rc);
-}
-
-#ifdef HAVE_KQUEUE
-/* ensure rb_wait_for_single_fd works on kqueue descriptors */
-#include <sys/types.h>
-#include <sys/time.h>
-#include <sys/event.h>
-static VALUE
-kqueue_test_wait(VALUE klass)
-{
-    int kqfd = -1;
-    int p[2] = { -1, -1 };
-    struct timeval tv = { 0, 0 };
-    const struct timespec ts = { 1, 0 };
-    struct kevent kev;
-    const char *msg;
-    VALUE ret = Qfalse;
-    int e = 0;
-    int n;
-
-    msg = "pipe";
-    if (rb_cloexec_pipe(p) < 0) goto err;
-
-    msg = "kqueue";
-    kqfd = kqueue();
-    if (kqfd < 0) goto err;
-
-    n = rb_wait_for_single_fd(kqfd, RB_WAITFD_IN, &tv);
-    if (n != 0) {
-        msg = "spurious wakeup";
-        errno = 0;
-        goto err;
-    }
-
-    msg = "write";
-    if (write(p[1], "", 1) < 0) goto err;
-
-    EV_SET(&kev, p[0], EVFILT_READ, EV_ADD, 0, 0, 0);
-
-    msg = "kevent";
-    n = kevent(kqfd, &kev, 1, &kev, 1, &ts);
-    if (n < 0) goto err;
-    msg = NULL;
-    if (n == 1) {
-        n = rb_wait_for_single_fd(kqfd, RB_WAITFD_IN, &tv);
-        ret = INT2NUM(n);
-    }
-    else {
-        rb_warn("kevent did not return readiness");
-    }
-err:
-    if (msg) e = errno;
-    if (p[0] >= 0) close(p[0]);
-    if (p[1] >= 0) close(p[1]);
-    if (kqfd >= 0) close(kqfd);
-    if (msg) {
-        if (e) rb_syserr_fail(e, msg);
-        rb_raise(rb_eRuntimeError, "%s", msg);
-    }
-    return ret;
-}
-#endif /* HAVE_KQUEUE */
-
-void
-Init_wait_for_single_fd(void)
-{
-    rb_define_const(rb_cObject, "RB_WAITFD_IN", INT2NUM(RB_WAITFD_IN));
-    rb_define_const(rb_cObject, "RB_WAITFD_OUT", INT2NUM(RB_WAITFD_OUT));
-    rb_define_const(rb_cObject, "RB_WAITFD_PRI", INT2NUM(RB_WAITFD_PRI));
-    rb_define_singleton_method(rb_cIO, "wait_for_single_fd",
-                               wait_for_single_fd, 3);
-#ifdef HAVE_KQUEUE
-    rb_define_singleton_method(rb_cIO, "kqueue_test_wait", kqueue_test_wait, 0);
-#endif
-}
diff --git a/ext/openssl/ossl_ssl.c b/ext/openssl/ossl_ssl.c
index c38142bfcc..0511579d7b 100644
--- a/ext/openssl/ossl_ssl.c
+++ b/ext/openssl/ossl_ssl.c
@@ -1639,12 +1639,12 @@ ossl_start_ssl(VALUE self, int (*func)(), const char *funcname, VALUE opts)
 	case SSL_ERROR_WANT_WRITE:
             if (no_exception_p(opts)) { return sym_wait_writable; }
             write_would_block(nonblock);
-            rb_io_wait_writable(fptr->fd);
+            rb_io_maybe_wait_writable(errno, fptr->self, Qnil);
             continue;
 	case SSL_ERROR_WANT_READ:
             if (no_exception_p(opts)) { return sym_wait_readable; }
             read_would_block(nonblock);
-            rb_io_wait_readable(fptr->fd);
+            rb_io_maybe_wait_readable(errno, fptr->self, Qnil);
             continue;
 	case SSL_ERROR_SYSCALL:
 #ifdef __APPLE__
@@ -1819,12 +1819,12 @@ ossl_ssl_read_internal(int argc, VALUE *argv, VALUE self, int nonblock)
 	    case SSL_ERROR_WANT_WRITE:
 		if (no_exception_p(opts)) { return sym_wait_writable; }
                 write_would_block(nonblock);
-                rb_io_wait_writable(fptr->fd);
+                rb_io_maybe_wait_writable(errno, fptr->self, Qnil);
                 continue;
 	    case SSL_ERROR_WANT_READ:
 		if (no_exception_p(opts)) { return sym_wait_readable; }
                 read_would_block(nonblock);
-                rb_io_wait_readable(fptr->fd);
+                rb_io_maybe_wait_readable(errno, fptr->self, Qnil);
 		continue;
 	    case SSL_ERROR_SYSCALL:
 		if (!ERR_peek_error()) {
@@ -1935,12 +1935,12 @@ ossl_ssl_write_internal(VALUE self, VALUE str, VALUE opts)
 	    case SSL_ERROR_WANT_WRITE:
 		if (no_exception_p(opts)) { return sym_wait_writable; }
                 write_would_block(nonblock);
-                rb_io_wait_writable(fptr->fd);
+                rb_io_maybe_wait_writable(errno, fptr->self, Qnil);
                 continue;
 	    case SSL_ERROR_WANT_READ:
 		if (no_exception_p(opts)) { return sym_wait_readable; }
                 read_would_block(nonblock);
-                rb_io_wait_readable(fptr->fd);
+                rb_io_maybe_wait_readable(errno, fptr->self, Qnil);
                 continue;
 	    case SSL_ERROR_SYSCALL:
 #ifdef __APPLE__
diff --git a/ext/socket/ancdata.c b/ext/socket/ancdata.c
index 546a971760..4ec3f3d0a8 100644
--- a/ext/socket/ancdata.c
+++ b/ext/socket/ancdata.c
@@ -1279,7 +1279,7 @@ bsock_sendmsg_internal(VALUE sock, VALUE data, VALUE vflags,
 
     if (ss == -1) {
 	int e;
-        if (!nonblock && rb_io_wait_writable(fptr->fd)) {
+        if (!nonblock && rb_io_maybe_wait_writable(errno, fptr->self, Qnil)) {
             rb_io_check_closed(fptr);
             goto retry;
         }
@@ -1551,7 +1551,7 @@ bsock_recvmsg_internal(VALUE sock,
 
     if (ss == -1) {
 	int e;
-        if (!nonblock && rb_io_wait_readable(fptr->fd)) {
+        if (!nonblock && rb_io_maybe_wait_readable(errno, fptr->self, Qnil)) {
             rb_io_check_closed(fptr);
             goto retry;
         }
diff --git a/ext/socket/basicsocket.c b/ext/socket/basicsocket.c
index 6168698df1..05172100c8 100644
--- a/ext/socket/basicsocket.c
+++ b/ext/socket/basicsocket.c
@@ -537,12 +537,11 @@ bsock_remote_address(VALUE sock)
  *   }
  */
 VALUE
-rsock_bsock_send(int argc, VALUE *argv, VALUE sock)
+rsock_bsock_send(int argc, VALUE *argv, VALUE socket)
 {
     struct rsock_send_arg arg;
     VALUE flags, to;
     rb_io_t *fptr;
-    ssize_t n;
     rb_blocking_function_t *func;
     const char *funcname;
 
@@ -550,28 +549,38 @@ rsock_bsock_send(int argc, VALUE *argv, VALUE sock)
 
     StringValue(arg.mesg);
     if (!NIL_P(to)) {
-	SockAddrStringValue(to);
-	to = rb_str_new4(to);
-	arg.to = (struct sockaddr *)RSTRING_PTR(to);
-	arg.tolen = RSTRING_SOCKLEN(to);
-	func = rsock_sendto_blocking;
-	funcname = "sendto(2)";
+        SockAddrStringValue(to);
+        to = rb_str_new4(to);
+        arg.to = (struct sockaddr *)RSTRING_PTR(to);
+        arg.tolen = RSTRING_SOCKLEN(to);
+        func = rsock_sendto_blocking;
+        funcname = "sendto(2)";
     }
     else {
-	func = rsock_send_blocking;
-	funcname = "send(2)";
+        func = rsock_send_blocking;
+        funcname = "send(2)";
     }
-    GetOpenFile(sock, fptr);
+
+    RB_IO_POINTER(socket, fptr);
+
     arg.fd = fptr->fd;
     arg.flags = NUM2INT(flags);
-    while (rsock_maybe_fd_writable(arg.fd),
-	   (n = (ssize_t)BLOCKING_REGION_FD(func, &arg)) < 0) {
-	if (rb_io_maybe_wait_writable(errno, sock, Qnil)) {
-	    continue;
-	}
-	rb_sys_fail(funcname);
+
+    while (true) {
+#ifdef RSOCK_WAIT_BEFORE_BLOCKING
+        rb_io_wait(socket, RB_INT2NUM(RUBY_IO_WRITABLE), Qnil);
+#endif
+
+        ssize_t n = (ssize_t)BLOCKING_REGION_FD(func, &arg);
+
+        if (n >= 0) return SSIZET2NUM(n);
+
+        if (rb_io_maybe_wait_writable(errno, socket, Qnil)) {
+            continue;
+        }
+
+        rb_sys_fail(funcname);
     }
-    return SSIZET2NUM(n);
 }
 
 /*
diff --git a/ext/socket/init.c b/ext/socket/init.c
index 8eb8c8e901..5859c33e29 100644
--- a/ext/socket/init.c
+++ b/ext/socket/init.c
@@ -198,7 +198,10 @@ rsock_s_recvfrom(VALUE socket, int argc, VALUE *argv, enum sock_recv_type from)
 
     while (true) {
         rb_io_check_closed(fptr);
-        rsock_maybe_wait_fd(arg.fd);
+
+#ifdef RSOCK_WAIT_BEFORE_BLOCKING
+        rb_io_wait(fptr->self, RB_INT2NUM(RUBY_IO_READABLE), Qnil);
+#endif
 
         slen = (long)rb_str_locktmp_ensure(str, recvfrom_locktmp, (VALUE)&arg);
 
@@ -701,11 +704,13 @@ rsock_s_accept(VALUE klass, VALUE io, struct sockaddr *sockaddr, socklen_t *len)
       .len = len
     };
 
-    int retry = 0;
+    int retry = 0, peer;
 
   retry:
-    rsock_maybe_wait_fd(accept_arg.fd);
-    int peer = (int)BLOCKING_REGION_FD(accept_blocking, &accept_arg);
+#ifdef RSOCK_WAIT_BEFORE_BLOCKING
+    rb_io_wait(fptr->self, RB_INT2NUM(RUBY_IO_READABLE), Qnil);
+#endif
+    peer = (int)BLOCKING_REGION_FD(accept_blocking, &accept_arg);
     if (peer < 0) {
         int error = errno;
 
diff --git a/ext/socket/rubysocket.h b/ext/socket/rubysocket.h
index a7755660e9..c0d40addca 100644
--- a/ext/socket/rubysocket.h
+++ b/ext/socket/rubysocket.h
@@ -432,30 +432,17 @@ NORETURN(void rsock_sys_fail_sockaddr(const char *, struct sockaddr *addr, sockl
 NORETURN(void rsock_sys_fail_raddrinfo(const char *, VALUE rai));
 NORETURN(void rsock_sys_fail_raddrinfo_or_sockaddr(const char *, VALUE addr, VALUE rai));
 
-/*
- * It is safe on Linux to attempt using a socket without waiting on it in
- * all cases.  For some syscalls (e.g. accept/accept4), blocking on the
- * syscall instead of relying on select/poll allows the kernel to use
- * "wake-one" behavior and avoid the thundering herd problem.
- * This is likely safe on all other *nix-like systems, so this safe list
- * can be expanded by interested parties.
- */
-#if defined(__linux__)
-static inline int rsock_maybe_fd_writable(int fd) { return 1; }
-static inline void rsock_maybe_wait_fd(int fd) { }
-#  ifdef MSG_DONTWAIT
-#    define MSG_DONTWAIT_RELIABLE 1
-#  endif
-#else /* some systems (mswin/mingw) need these.  ref: r36946 */
-#  define rsock_maybe_fd_writable(fd) rb_thread_fd_writable((fd))
-#  define rsock_maybe_wait_fd(fd) rb_thread_wait_fd((fd))
+#if defined(__MINGW32__) || defined(_WIN32)
+#define RSOCK_WAIT_BEFORE_BLOCKING
 #endif
 
 /*
  * some OSes may support MSG_DONTWAIT inconsistently depending on socket
  * type, we only expect Linux to support it consistently for all socket types.
  */
-#ifndef MSG_DONTWAIT_RELIABLE
+#if defined(MSG_DONTWAIT) && defined(__linux__)
+#  define MSG_DONTWAIT_RELIABLE 1
+#else
 #  define MSG_DONTWAIT_RELIABLE 0
 #endif
 
diff --git a/ext/socket/udpsocket.c b/ext/socket/udpsocket.c
index 593f05522d..94ea19c224 100644
--- a/ext/socket/udpsocket.c
+++ b/ext/socket/udpsocket.c
@@ -153,23 +153,26 @@ udp_send_internal(VALUE v)
 {
     struct udp_send_arg *arg = (void *)v;
     rb_io_t *fptr;
-    int n;
     struct addrinfo *res;
 
     rb_io_check_closed(fptr = arg->fptr);
     for (res = arg->res->ai; res; res = res->ai_next) {
       retry:
-	arg->sarg.fd = fptr->fd;
-	arg->sarg.to = res->ai_addr;
-	arg->sarg.tolen = res->ai_addrlen;
-	rsock_maybe_fd_writable(arg->sarg.fd);
-	n = (int)BLOCKING_REGION_FD(rsock_sendto_blocking, &arg->sarg);
-	if (n >= 0) {
-	    return INT2FIX(n);
-	}
-	if (rb_io_wait_writable(fptr->fd)) {
-	    goto retry;
-	}
+        arg->sarg.fd = fptr->fd;
+        arg->sarg.to = res->ai_addr;
+        arg->sarg.tolen = res->ai_addrlen;
+
+#ifdef RSOCK_WAIT_BEFORE_BLOCKING
+        rb_io_wait(fptr->self, RB_INT2NUM(RUBY_IO_WRITABLE), Qnil);
+#endif
+
+        ssize_t n = (ssize_t)BLOCKING_REGION_FD(rsock_sendto_blocking, &arg->sarg);
+
+        if (n >= 0) return RB_INT2NUM(n);
+
+        if (rb_io_maybe_wait_writable(errno, fptr->self, Qnil)) {
+            goto retry;
+        }
     }
     return Qfalse;
 }
diff --git a/include/ruby/internal/intern/thread.h b/include/ruby/internal/intern/thread.h
index a12a371058..dd591474ce 100644
--- a/include/ruby/internal/intern/thread.h
+++ b/include/ruby/internal/intern/thread.h
@@ -31,8 +31,8 @@ struct timeval;
 
 /* thread.c */
 void rb_thread_schedule(void);
-void rb_thread_wait_fd(int);
-int rb_thread_fd_writable(int);
+#define rb_thread_wait_fd(fd) rb_wait_for_single_fd((fd), RUBY_IO_READABLE, NULL)
+#define rb_thread_fd_writable(fd) rb_wait_for_single_fd((fd), RUBY_IO_WRITABLE, NULL)
 void rb_thread_fd_close(int);
 int rb_thread_alone(void);
 void rb_thread_sleep(int);
diff --git a/include/ruby/io.h b/include/ruby/io.h
index bf916a5f8e..9a6b65cb2c 100644
--- a/include/ruby/io.h
+++ b/include/ruby/io.h
@@ -154,8 +154,13 @@ int rb_io_extract_encoding_option(VALUE opt, rb_encoding **enc_p, rb_encoding **
 void rb_io_extract_modeenc(VALUE *vmode_p, VALUE *vperm_p, VALUE opthash, int *oflags_p, int *fmode_p, rb_io_enc_t *convconfig_p);
 ssize_t rb_io_bufwrite(VALUE io, const void *buf, size_t size);
 
+RBIMPL_ATTR_DEPRECATED(("use rb_io_maybe_wait_readable"))
 int rb_io_wait_readable(int fd);
+
+RBIMPL_ATTR_DEPRECATED(("use rb_io_maybe_wait_writable"))
 int rb_io_wait_writable(int fd);
+
+RBIMPL_ATTR_DEPRECATED(("use rb_io_wait"))
 int rb_wait_for_single_fd(int fd, int events, struct timeval *tv);
 
 VALUE rb_io_wait(VALUE io, VALUE events, VALUE timeout);
diff --git a/io.c b/io.c
index c5cd348f4d..7db0560e71 100644
--- a/io.c
+++ b/io.c
@@ -492,7 +492,7 @@ rb_cloexec_fcntl_dupfd(int fd, int minfd)
 
 #if defined(_WIN32)
 #define WAIT_FD_IN_WIN32(fptr) \
-    (rb_w32_io_cancelable_p((fptr)->fd) ? 0 : rb_thread_wait_fd((fptr)->fd))
+    (rb_w32_io_cancelable_p((fptr)->fd) ? 0 : RB_NUM2INT(rb_io_wait(fptr->self, RB_INT2NUM(RUBY_IO_READABLE), Qnil)))
 #else
 #define WAIT_FD_IN_WIN32(fptr)
 #endif
@@ -998,7 +998,7 @@ void
 rb_io_read_check(rb_io_t *fptr)
 {
     if (!READ_DATA_PENDING(fptr)) {
-	rb_thread_wait_fd(fptr->fd);
+        rb_io_wait(fptr->self, RB_INT2NUM(RUBY_IO_READABLE), Qnil);
     }
     return;
 }
@@ -1248,13 +1248,17 @@ static int
 io_fflush(rb_io_t *fptr)
 {
     rb_io_check_closed(fptr);
+
     if (fptr->wbuf.len == 0)
         return 0;
+
     while (fptr->wbuf.len > 0 && io_flush_buffer(fptr) != 0) {
-	if (!rb_io_wait_writable(fptr->fd))
-	    return -1;
+        if (!rb_io_maybe_wait_writable(errno, fptr->self, Qnil))
+            return -1;
+
         rb_io_check_closed(fptr);
     }
+
     return 0;
 }
 
@@ -1296,11 +1300,25 @@ rb_io_wait(VALUE io, VALUE events, VALUE timeout)
 }
 
 static VALUE
-rb_io_from_fd(int fd)
+io_from_fd(int fd)
 {
     return prep_io(fd, FMODE_PREP, rb_cIO, NULL);
 }
 
+static
+int io_wait_for_single_fd(int fd, int events, struct timeval *timeout)
+{
+    VALUE scheduler = rb_fiber_scheduler_current();
+
+    if (scheduler != Qnil) {
+        return RTEST(
+            rb_fiber_scheduler_io_wait(scheduler, io_from_fd(fd), RB_INT2NUM(events), rb_fiber_scheduler_make_timeout(timeout))
+        );
+    }
+
+    return rb_thread_wait_for_single_fd(fd, events, timeout);
+}
+
 int
 rb_io_wait_readable(int f)
 {
@@ -1322,11 +1340,11 @@ rb_io_wait_readable(int f)
 #endif
         if (scheduler != Qnil) {
             return RTEST(
-                rb_fiber_scheduler_io_wait_readable(scheduler, rb_io_from_fd(f))
+                rb_fiber_scheduler_io_wait_readable(scheduler, io_from_fd(f))
             );
         }
         else {
-            rb_thread_wait_fd(f);
+            io_wait_for_single_fd(f, RUBY_IO_READABLE, NULL);
         }
         return TRUE;
 
@@ -1365,11 +1383,11 @@ rb_io_wait_writable(int f)
 #endif
         if (scheduler != Qnil) {
             return RTEST(
-                rb_fiber_scheduler_io_wait_writable(scheduler, rb_io_from_fd(f))
+                rb_fiber_scheduler_io_wait_writable(scheduler, io_from_fd(f))
             );
         }
         else {
-            rb_thread_fd_writable(f);
+            io_wait_for_single_fd(f, RUBY_IO_WRITABLE, NULL);
         }
         return TRUE;
 
@@ -1381,20 +1399,19 @@ rb_io_wait_writable(int f)
 int
 rb_wait_for_single_fd(int fd, int events, struct timeval *timeout)
 {
-    VALUE scheduler = rb_fiber_scheduler_current();
-
-    if (scheduler != Qnil) {
-        return RTEST(
-            rb_fiber_scheduler_io_wait(scheduler, rb_io_from_fd(fd), RB_INT2NUM(events), rb_fiber_scheduler_make_timeout(timeout))
-        );
-    }
-
-    return rb_thread_wait_for_single_fd(fd, events, timeout);
+    return io_wait_for_single_fd(fd, events, timeout);
 }
 
 VALUE rb_io_maybe_wait(int error, VALUE io, VALUE events, VALUE timeout)
 {
     switch (error) {
+      // In old Linux, several special files under /proc and /sys don't handle
+      // select properly. Thus we need avoid to call if don't use O_NONBLOCK.
+      // Otherwise, we face nasty hang up. Sigh.
+      // e.g. http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=31b07093c44a7a442394d44423e21d783f5523b8
+      // http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=31b07093c44a7a442394d44423e21d783f5523b8
+      // In EINTR case, we only need to call RUBY_VM_CHECK_INTS_BLOCKING().
+      // Then rb_thread_check_ints() is enough.
       case EINTR:
 #if defined(ERESTART)
       case ERESTART:
@@ -1561,9 +1578,6 @@ io_binwrite_string(VALUE arg)
 	    return len;
     }
 
-    if (fptr->stdio_file != stderr && !rb_thread_fd_writable(fptr->fd))
-	rb_io_check_closed(fptr);
-
     return rb_write_internal(p->fptr->fd, p->ptr, p->length);
 }
 #endif
@@ -1623,7 +1637,7 @@ io_binwrite(VALUE str, const char *ptr, long len, rb_io_t *fptr, int nosync)
 	}
 	if (r == -2L)
 	    return -1L;
-        if (rb_io_wait_writable(fptr->fd)) {
+        if (rb_io_maybe_wait_writable(errno, fptr->self, Qnil)) {
             rb_io_check_closed(fptr);
 	    if (offset < len)
 		goto retry;
@@ -1861,7 +1875,7 @@ io_binwritev(struct iovec *iov, int iovcnt, rb_io_t *fptr)
 
 	errno = EAGAIN;
     }
-    if (rb_io_wait_writable(fptr->fd)) {
+    if (rb_io_maybe_wait_writable(errno, fptr->self, Qnil)) {
 	rb_io_check_closed(fptr);
 	goto retry;
     }
@@ -2250,7 +2264,7 @@ rb_io_rewind(VALUE io)
 static int
 fptr_wait_readable(rb_io_t *fptr)
 {
-    int ret = rb_io_wait_readable(fptr->fd);
+    int ret = rb_io_maybe_wait_readable(errno, fptr->self, Qnil);
 
     if (ret)
         rb_io_check_closed(fptr);
@@ -4689,7 +4703,7 @@ finish_writeconv(rb_io_t *fptr, int noalloc)
                 if (0 <= r) {
                     ds += r;
                 }
-                if (rb_io_wait_writable(fptr->fd)) {
+                if (rb_io_maybe_wait_writable(errno, fptr->self, Qnil)) {
                     if (fptr->fd < 0)
                         return noalloc ? Qtrue : rb_exc_new3(rb_eIOError, rb_str_new_cstr(closed_stream));
                     goto retry;
@@ -5332,7 +5346,7 @@ rb_io_sysread(int argc, VALUE *argv, VALUE io)
     rb_io_check_byte_readable(fptr);
 
     if (READ_DATA_BUFFERED(fptr)) {
-	rb_raise(rb_eIOError, "sysread for buffered IO");
+        rb_raise(rb_eIOError, "sysread for buffered IO");
     }
 
     /*
@@ -5342,7 +5356,7 @@ rb_io_sysread(int argc, VALUE *argv, VALUE io)
      * the IO after we return from rb_thread_wait_fd() but before
      * we call read()
      */
-    rb_thread_wait_fd(fptr->fd);
+    rb_io_wait(fptr->self, RB_INT2NUM(RUBY_IO_READABLE), Qnil);
 
     rb_io_check_closed(fptr);
 
@@ -11104,7 +11118,7 @@ rb_thread_fiber_scheduler_wait_for_single_fd(void * _args)
 {
     struct wait_for_single_fd *args = (struct wait_for_single_fd *)_args;
 
-    args->result = rb_fiber_scheduler_io_wait(args->scheduler, rb_io_from_fd(args->fd), INT2NUM(args->events), Qnil);
+    args->result = rb_fiber_scheduler_io_wait(args->scheduler, io_from_fd(args->fd), INT2NUM(args->events), Qnil);
 
     return NULL;
 }
@@ -11170,12 +11184,12 @@ maygvl_copy_stream_wait_read(int has_gvl, struct copy_stream_struct *stp)
     int ret;
 
     do {
-	if (has_gvl) {
-	    ret = rb_wait_for_single_fd(stp->src_fd, RB_WAITFD_IN, NULL);
-	}
-	else {
-	    ret = nogvl_wait_for_single_fd(stp->th, stp->src_fd, RB_WAITFD_IN);
-	}
+        if (has_gvl) {
+            ret = RB_NUM2INT(rb_io_wait(stp->src, RB_INT2NUM(RUBY_IO_READABLE), Qnil));
+        }
+        else {
+            ret = nogvl_wait_for_single_fd(stp->th, stp->src_fd, RB_WAITFD_IN);
+        }
     } while (ret < 0 && maygvl_copy_stream_continue_p(has_gvl, stp));
 
     if (ret < 0) {
diff --git a/ruby.c b/ruby.c
index 0247c581b7..baa2f251c2 100644
--- a/ruby.c
+++ b/ruby.c
@@ -2305,7 +2305,7 @@ open_load_file(VALUE fname_v, int *xflag)
 	      We need to wait if FIFO is empty. It's FIFO's semantics.
 	      rb_thread_wait_fd() release GVL. So, it's safe.
 	    */
-	    rb_thread_wait_fd(fd);
+	    rb_io_wait(f, RB_INT2NUM(RUBY_IO_READABLE), Qnil);
 	}
     }
     return f;
diff --git a/thread.c b/thread.c
index 1511977d4d..ed771166e6 100644
--- a/thread.c
+++ b/thread.c
@@ -4296,39 +4296,6 @@ do_select(VALUE p)
     return (VALUE)result;
 }
 
-static void
-rb_thread_wait_fd_rw(int fd, int read)
-{
-    int result = 0;
-    int events = read ? RB_WAITFD_IN : RB_WAITFD_OUT;
-
-    thread_debug("rb_thread_wait_fd_rw(%d, %s)\n", fd, read ? "read" : "write");
-
-    if (fd < 0) {
-	rb_raise(rb_eIOError, "closed stream");
-    }
-
-    result = rb_wait_for_single_fd(fd, events, NULL);
-    if (result < 0) {
-	rb_sys_fail(0);
-    }
-
-    thread_debug("rb_thread_wait_fd_rw(%d, %s): done\n", fd, read ? "read" : "write");
-}
-
-void
-rb_thread_wait_fd(int fd)
-{
-    rb_thread_wait_fd_rw(fd, 1);
-}
-
-int
-rb_thread_fd_writable(int fd)
-{
-    rb_thread_wait_fd_rw(fd, 0);
-    return TRUE;
-}
-
 static rb_fdset_t *
 init_set_fd(int fd, rb_fdset_t *fds)
 {