fix fiber segfault (#595)

Author: mensfeld

CHANGELOG.md

@@ -6,6 +6,7 @@
 - [Enhancement] Allow native Kafka customization poll time.
 - [Enhancement] Roll out experimental jruby support.
 - [Fix] Fix issue where post-closed producer C topics refs would not be cleaned.
+- [Fix] Fiber causes Segmentation Fault.
 
 ## 0.21.0 (2025-02-13)
 - [Enhancement] Bump librdkafka to `2.8.0`

lib/rdkafka/native_kafka.rb

@@ -131,6 +131,8 @@ def close(object_id=nil)
         Rdkafka::Bindings.rd_kafka_destroy(@inner)
         @inner = nil
         @opaque = nil
+        @poll_mutex.unlock
+        @poll_mutex = nil
       end
     end
   end

spec/rdkafka/producer_spec.rb

@@ -973,4 +973,19 @@ def call(_, handle)
       end
     end
   end
+
+  describe 'with other fiber closing' do
+    context 'when we create many fibers and close producer in some of them' do
+      it 'expect not to crash ruby' do
+        10.times do |i|
+          producer = rdkafka_producer_config.producer
+
+          Fiber.new do
+            GC.start
+            producer.close
+          end.resume
+        end
+      end
+    end
+  end
 end