Prevent crashes from get_main_hub when in trap context

sentry-ruby/lib/sentry-ruby.rb

@@ -308,6 +308,9 @@ def csp_report_uri
     # @return [Hub]
     def get_main_hub
       MUTEX.synchronize { @main_hub }
+    rescue ThreadError
+      # In some rare cases this may be called in a trap context so we need to handle it gracefully
+      @main_hub
     end
 
     # Takes an instance of Sentry::Breadcrumb and stores it to the current active scope.

sentry-ruby/spec/sentry_spec.rb

@@ -70,6 +70,44 @@
         end
       end
     end
+
+    context "works within a trap context" do
+      it "reproduces mutex issue in trap handler" do
+        read_pipe, write_pipe = IO.pipe
+
+        pid = fork do
+          read_pipe.close
+
+          described_class.init do |config|
+            config.dsn = Sentry::TestHelper::DUMMY_DSN
+          end
+
+          trap('HUP') do
+            hub = described_class.get_main_hub
+            write_pipe.write(hub.class.to_s)
+            write_pipe.close
+          end
+
+          Process.kill('HUP', Process.pid)
+        end
+
+        write_pipe.close
+
+        start_time = Time.now
+        timeout = 1.0
+        result = nil
+
+        while Time.now - start_time < timeout
+          break if Process.wait(pid, Process::WNOHANG)
+          sleep 0.01
+        end
+
+        result = read_pipe.read unless read_pipe.closed?
+        read_pipe.close
+
+        expect(result).to eq("Sentry::Hub")
+      end
+    end
   end
 
   describe "#clone_hub_to_current_thread" do