io + socket: make pipes and sockets nonblocking by default

All normal Ruby IO methods (IO#read, IO#gets, IO#write, ...) are
all capable of appearing to be "blocking" when presented with a
file description with the O_NONBLOCK flag set; so there is
little risk of incompatibility within Ruby-using programs.

The biggest compatibility risk is when spawning external
programs.  As a result, stdin, stdout, and stderr are now always
made blocking before exec-family calls.

This change will make an event-oriented MJIT usable if it is
waiting on pipes on POSIX_like platforms.

It is ALSO necessary to take advantage of (proposed lightweight
concurrency (aka "auto-Fiber") or any similar proposal for
network concurrency: https://bugs.ruby-lang.org/issues/13618

Named-pipe (FIFO) are NOT yet non-blocking by default since
they are rarely-used and may introduce compatibility problems
and extra syscall overhead for a common path.

Please revert this commit if there are problems and if I am afk
since I am afk a lot, lately.

[ruby-core:89950] [Bug #14968]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65922 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 14 insertions, 3 deletions

diff --git a/win32/win32.c b/win32/win32.c
index 820b16c40b..d28bd56452 100644
--- a/win32/win32.c
+++ b/win32/win32.c
@@ -4429,11 +4429,11 @@ fcntl(int fd, int cmd, ...)
 
 /* License: Ruby's */
 int
-rb_w32_set_nonblock(int fd)
+rb_w32_set_nonblock2(int fd, int nonblock)
 {
     SOCKET sock = TO_SOCKET(fd);
     if (is_socket(sock)) {
-	return setfl(sock, O_NONBLOCK);
+	return setfl(sock, nonblock ? O_NONBLOCK : 0);
     }
     else if (is_pipe(sock)) {
 	DWORD state;
@@ -4441,7 +4441,12 @@ rb_w32_set_nonblock(int fd)
 	    errno = map_errno(GetLastError());
 	    return -1;
 	}
-	state |= PIPE_NOWAIT;
+        if (nonblock) {
+            state |= PIPE_NOWAIT;
+        }
+        else {
+            state &= ~PIPE_NOWAIT;
+        }
 	if (!SetNamedPipeHandleState((HANDLE)sock, &state, NULL, NULL)) {
 	    errno = map_errno(GetLastError());
 	    return -1;
@@ -4454,6 +4459,12 @@ rb_w32_set_nonblock(int fd)
     }
 }
 
+int
+rb_w32_set_nonblock(int fd)
+{
+    return rb_w32_set_nonblock2(fd, TRUE);
+}
+
 #ifndef WNOHANG
 #define WNOHANG -1
 #endif