introduce rb_nogvl C-API to mark ubf as async-signal-safe

zlib and bignum both contain unblocking functions which are
async-signal-safe and do not require spawning additional
threads.

We can execute those functions directly in signal handlers
without incurring overhead of extra threads, so provide C-API
users the ability to deal with that.  Other C-API users may
have similar need.

This flexible API can supercede existing uses of
rb_thread_call_without_gvl and rb_thread_call_without_gvl2 by
introducing a flags argument to control behavior.

Note: this API is NOT finalized.  It needs approval from other
committers.  I prefer shorter name than previous
rb_thread_call_without_gvl* functions because my eyes requires
big fonts.

[Bug #15499]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66712 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 20 insertions, 0 deletions

diff --git a/test/-ext-/gvl/test_ubf_async_safe.rb b/test/-ext-/gvl/test_ubf_async_safe.rb
new file mode 100644
index 0000000000..85c4a7d38e
--- /dev/null
+++ b/test/-ext-/gvl/test_ubf_async_safe.rb
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+class TestUbfAsyncSafe < Test::Unit::TestCase
+  def test_ubf_async_safe
+    skip 'need fork for single-threaded test' unless Process.respond_to?(:fork)
+    IO.pipe do |r, w|
+      pid = fork do
+        require '-test-/gvl/call_without_gvl'
+        r.close
+        trap(:INT) { exit!(0) }
+        Thread.current.__ubf_async_safe__(w.fileno)
+        exit!(1)
+      end
+      w.close
+      assert IO.select([r], nil, nil, 30), 'child did not become ready'
+      Process.kill(:INT, pid)
+      _, st = Process.waitpid2(pid)
+      assert_predicate st, :success?, ':INT signal triggered exit'
+    end
+  end
+end