[PATCH] epollexclusive: handle future rb_io_t deprecation

[PATCH] epollexclusive: handle future rb_io_t deprecation

[Eric Wong]

From: Eric Wong <bofh@yhbt.net>

It looks like Ruby 3.3+ will hide rb_io_t internals and
get rid of the venerable `GetOpenFile' macro in favor of
`rb_io_descriptor'.  `rb_io_descriptor' has been public
API since Ruby 3.1 and should be safe to use, and
is necessary for `raindrops' (a dependency of ours):

  https://yhbt.net/raindrops-public/20230609104805.39022-1-samuel.williams@oriontransfer.co.nz/
  https://bugs.ruby-lang.org/issues/19057#note-17

We'll also avoid an unnecessary call to `rb_io_get_io' in
`get_readers' since `epio' (aka `self') can only be of
the Unicorn::Waiter IO subclass.  However, we must still use
`rb_io_get_io' when handling non-self args in `prep_readers'.
---
 Note: I've only tested this patch on 2.7 atm, ENOSPC.

 ext/unicorn_http/epollexclusive.h | 27 ++++++++++++++++++---------
 ext/unicorn_http/extconf.rb       |  4 +++-
 2 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/ext/unicorn_http/epollexclusive.h b/ext/unicorn_http/epollexclusive.h
index 8f4ea9a0..c74a7799 100644
--- a/ext/unicorn_http/epollexclusive.h
+++ b/ext/unicorn_http/epollexclusive.h
@@ -22,6 +22,18 @@
 #endif
 
 #if USE_EPOLL
+#if defined(HAVE_RB_IO_DESCRIPTOR) /* Ruby 3.1+ */
+#	define my_fileno(io) rb_io_descriptor(io)
+#else /* Ruby <3.1 */
+static int my_fileno(VALUE io)
+{
+	rb_io_t *fptr;
+	GetOpenFile(io, fptr);
+	rb_io_check_closed(fptr);
+	return fptr->fd;
+}
+#endif /* Ruby <3.1 */
+
 /*
  * :nodoc:
  * returns IO object if EPOLLEXCLUSIVE works and arms readers
@@ -38,9 +50,8 @@ static VALUE prep_readers(VALUE cls, VALUE readers)
 
 	Check_Type(readers, T_ARRAY);
 	for (i = 0; i < RARRAY_LEN(readers); i++) {
-		int rc;
+		int rc, fd;
 		struct epoll_event e;
-		rb_io_t *fptr;
 		VALUE io = rb_ary_entry(readers, i);
 
 		e.data.u64 = i; /* the reason readers shouldn't change */
@@ -53,9 +64,8 @@ static VALUE prep_readers(VALUE cls, VALUE readers)
 		 * cycles on maintaining level-triggering.
 		 */
 		e.events = EPOLLEXCLUSIVE | EPOLLIN;
-		io = rb_io_get_io(io);
-		GetOpenFile(io, fptr);
-		rc = epoll_ctl(epfd, EPOLL_CTL_ADD, fptr->fd, &e);
+		fd = my_fileno(rb_io_get_io(io));
+		rc = epoll_ctl(epfd, EPOLL_CTL_ADD, fd, &e);
 		if (rc < 0) rb_sys_fail("epoll_ctl");
 	}
 	return epio;
@@ -65,7 +75,7 @@ static VALUE prep_readers(VALUE cls, VALUE readers)
 #if USE_EPOLL
 struct ep_wait {
 	struct epoll_event event;
-	rb_io_t *fptr;
+	int epfd;
 	int timeout_msec;
 };
 
@@ -78,7 +88,7 @@ static void *do_wait(void *ptr) /* runs w/o GVL */
 	 * at-a-time (c.f. fs/eventpoll.c in linux.git, it's quite
 	 * easy-to-understand for anybody familiar with Ruby C).
 	 */
-	return (void *)(long)epoll_wait(epw->fptr->fd, &epw->event, 1,
+	return (void *)(long)epoll_wait(epw->epfd, &epw->event, 1,
 					epw->timeout_msec);
 }
 
@@ -92,9 +102,8 @@ get_readers(VALUE epio, VALUE ready, VALUE readers, VALUE timeout_msec)
 
 	Check_Type(ready, T_ARRAY);
 	Check_Type(readers, T_ARRAY);
-	epio = rb_io_get_io(epio);
-	GetOpenFile(epio, epw.fptr);
 
+	epw.epfd = my_fileno(epio);
 	epw.timeout_msec = NUM2INT(timeout_msec);
 	n = (long)rb_thread_call_without_gvl(do_wait, &epw, RUBY_UBF_IO, NULL);
 	if (n < 0) {
diff --git a/ext/unicorn_http/extconf.rb b/ext/unicorn_http/extconf.rb
index 80d00e56..11099cd0 100644
--- a/ext/unicorn_http/extconf.rb
+++ b/ext/unicorn_http/extconf.rb
@@ -33,5 +33,7 @@
   message("no, needs Ruby 2.6+\n")
 end
 
-have_func('epoll_create1', %w(sys/epoll.h))
+if have_func('epoll_create1', %w(sys/epoll.h))
+  have_func('rb_io_descriptor') # Ruby 3.1+
+end
 create_makefile("unicorn_http")

Re: [PATCH] epollexclusive: handle future rb_io_t deprecation

[Jean Boussier]

Hello Eric,

Do you have any plans to merge this patch as well that the similar kgio one?

Re: [PATCH] epollexclusive: handle future rb_io_t deprecation

[Eric Wong]

Jean Boussier <jean.boussier@gmail.com> wrote:
> Hello Eric,
> 
> Do you have any plans to merge this patch as well that the similar kgio one?

Already merged a while back:
https://yhbt.net/unicorn.git/63c85c4282d15e22bd32a905883d2d0e149619d1/s/

Not I don't want to have to scramble for other changes in case
there's more incompatibilities introduced by Ruby (or Rack).
I'm also wary of increasing download counts due to MFA requirements
(both explained in more detail @
https://yhbt.net/kgio-public/20230828005810.M622269@dcvr/ )