fix: split lock in TracerProvider (#866)

* fix: split lock in TracerProvider

* silence the cop

Author: fbogsany

sdk/lib/opentelemetry/sdk/trace/tracer_provider.rb

@@ -33,6 +33,7 @@ def initialize(sampler: sampler_from_environment(Samplers.parent_based(root: Sam
                        span_limits: SpanLimits::DEFAULT)
           @mutex = Mutex.new
           @registry = {}
+          @registry_mutex = Mutex.new
           @span_processors = []
           @span_limits = span_limits
           @sampler = sampler
@@ -51,7 +52,7 @@ def tracer(name = nil, version = nil)
           name ||= ''
           version ||= ''
           OpenTelemetry.logger.warn 'calling TracerProvider#tracer without providing a tracer name.' if name.empty?
-          @mutex.synchronize { @registry[Key.new(name, version)] ||= Tracer.new(name, version, self) }
+          @registry_mutex.synchronize { @registry[Key.new(name, version)] ||= Tracer.new(name, version, self) }
         end
 
         # Attempts to stop all the activity for this {TracerProvider}. Calls

sdk/test/opentelemetry/sdk/trace/tracer_provider_test.rb

@@ -84,6 +84,15 @@
       mock_span_processor.verify
       mock_span_processor2.verify
     end
+
+    it 'does not deadlock if span processor is traced' do
+      span_processor = OpenTelemetry::SDK::Trace::SpanProcessor.new
+      tracer_provider.add_span_processor(span_processor)
+      span_processor.stub(:shutdown, ->(timeout: nil) { tracer_provider.tracer.in_span('shutdown') {} }) do # rubocop:disable Lint/UnusedBlockArgument
+        tracer_provider.shutdown
+      end
+      pass 'no deadlock'
+    end
   end
 
   describe '#force_flush' do