[Feature #10602] Add new API rb_profile_thread_frames()

Add a new API rb_profile_thread_frames(), which is essentialy a
per-thread version of rb_profile_frames().

While the original rb_profile_frames() always returns results about the
current active thread obtained by GET_EC(), this new API takes a Thread
to be profiled as an argument.

This should come in handy when profiling I/O-bound programs such as
webapps, since this new API allows us to learn about Threads performing
I/O (which do not have the GVL).

Profiling worker threads (such as Sidekiq workers) may be another
application.

Implements [Feature #10602]

Co-authored-by: Mike Perham <mike@perham.net>

1 files changed, 47 insertions, 0 deletions

diff --git a/test/-ext-/debug/test_profile_frames.rb b/test/-ext-/debug/test_profile_frames.rb
index 08aedf63c8..e66413c228 100644
--- a/test/-ext-/debug/test_profile_frames.rb
+++ b/test/-ext-/debug/test_profile_frames.rb
@@ -39,6 +39,20 @@ class SampleClassForTestProfileFrames
   end
 end
 
+class SampleClassForTestProfileThreadFrames
+  def initialize(mutex)
+    @mutex = mutex
+  end
+
+  def foo(block)
+    bar(block)
+  end
+
+  def bar(block)
+    block.call
+  end
+end
+
 class TestProfileFrames < Test::Unit::TestCase
   def test_profile_frames
     obj, frames = Fiber.new{
@@ -139,6 +153,39 @@ class TestProfileFrames < Test::Unit::TestCase
     }
   end
 
+  def test_profile_thread_frames
+    mutex = Mutex.new
+    th = Thread.new do
+      mutex.lock
+      Thread.stop
+      SampleClassForTestProfileThreadFrames.new(mutex).foo(lambda { mutex.unlock; loop { sleep(1) } } )
+    end
+
+    # ensure execution has reached SampleClassForTestProfileThreadFrames#bar before running profile_thread_frames
+    loop { break if th.status == "sleep"; sleep 0.1 }
+    th.run
+    mutex.lock # wait until SampleClassForTestProfileThreadFrames#bar has been called
+
+    frames = Bug::Debug.profile_thread_frames(th, 0, 10)
+
+    full_labels = [
+      "Kernel#sleep",
+      "TestProfileFrames#test_profile_thread_frames",
+      "Kernel#loop",
+      "TestProfileFrames#test_profile_thread_frames",
+      "SampleClassForTestProfileThreadFrames#bar",
+      "SampleClassForTestProfileThreadFrames#foo",
+      "TestProfileFrames#test_profile_thread_frames",
+    ]
+
+    frames.each.with_index do |frame, i|
+      assert_equal(full_labels[i], frame)
+    end
+
+    th.kill
+  end
+
+
   def test_matches_backtrace_locations_main_thread
     assert_equal(Thread.current, Thread.main)