merge revision(s) 8ce2fb9bbbaea14737c84385b1573f743a30f773,3a0f6ce1d31eefd8af01b50f3632a64d64e8f8c1: [Backport #19415]

	Only emit circular dependency warning for owned thread shields [Bug
	 #19415]

	If multiple threads attemps to load the same file concurrently
	it's not a circular dependency issue.

	So we check that the existing ThreadShield is owner by the current
	fiber before warning about circular dependencies.
	---
	 internal/thread.h                                     |  1 +
	 load.c                                                |  3 ++-
	 spec/ruby/core/kernel/shared/require.rb               | 11 +++++++++++
	 spec/ruby/fixtures/code/concurrent_require_fixture.rb |  4 ++++
	 test/ruby/test_require.rb                             |  3 ---
	 thread.c                                              | 11 +++++++++++
	 6 files changed, 29 insertions(+), 4 deletions(-)
	 create mode 100644 spec/ruby/fixtures/code/concurrent_require_fixture.rb

	Use Thread.pass until thread.stop? to wait for thread to block

	[Bug #19415]

	It should be more reliable
	---
	 spec/ruby/fixtures/code/concurrent_require_fixture.rb | 2 +-
	 1 file changed, 1 insertion(+), 1 deletion(-)

2 files changed, 15 insertions, 0 deletions

diff --git a/spec/ruby/core/kernel/shared/require.rb b/spec/ruby/core/kernel/shared/require.rb
index 9a2c38be1a..f4645b0242 100644
--- a/spec/ruby/core/kernel/shared/require.rb
+++ b/spec/ruby/core/kernel/shared/require.rb
@@ -237,6 +237,17 @@ describe :kernel_require, shared: true do
       }.should complain(/circular require considered harmful/, verbose: true)
       ScratchPad.recorded.should == [:loaded]
     end
+
+    ruby_bug "#17340", ''...'3.3' do
+      it "loads a file concurrently" do
+        path = File.expand_path "concurrent_require_fixture.rb", CODE_LOADING_DIR
+        ScratchPad.record(@object)
+        -> {
+          @object.require(path)
+        }.should_not complain(/circular require considered harmful/, verbose: true)
+        ScratchPad.recorded.join
+      end
+    end
   end
 
   describe "(non-extensioned path)" do
diff --git a/spec/ruby/fixtures/code/concurrent_require_fixture.rb b/spec/ruby/fixtures/code/concurrent_require_fixture.rb
new file mode 100644
index 0000000000..d4ce734183
--- /dev/null
+++ b/spec/ruby/fixtures/code/concurrent_require_fixture.rb
@@ -0,0 +1,4 @@
+object = ScratchPad.recorded
+thread = Thread.new { object.require(__FILE__) }
+Thread.pass until thread.stop?
+ScratchPad.record(thread)