From 1f9f6f6cfc57020ccb35f77872c56f069f337075 Mon Sep 17 00:00:00 2001 From: Brent Wheeldon Date: Thu, 2 Nov 2017 14:53:43 -0400 Subject: Prevent deadlocks with load interlock and DB lock. This fixes an issue where competing threads deadlock each other. - Thread A holds the load interlock but is blocked on getting the DB lock - Thread B holds the DB lock but is blocked on getting the load interlock (for example when there is a `Model.transaction` block that needs to autoload) This solution allows for dependency loading in other threads while a thread is waiting to acquire the DB lock. Fixes #31019 --- .../concurrency/load_interlock_aware_monitor.rb | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) create mode 100644 activesupport/lib/active_support/concurrency/load_interlock_aware_monitor.rb (limited to 'activesupport/lib/active_support/concurrency/load_interlock_aware_monitor.rb') diff --git a/activesupport/lib/active_support/concurrency/load_interlock_aware_monitor.rb b/activesupport/lib/active_support/concurrency/load_interlock_aware_monitor.rb new file mode 100644 index 0000000000..a8455c0048 --- /dev/null +++ b/activesupport/lib/active_support/concurrency/load_interlock_aware_monitor.rb @@ -0,0 +1,17 @@ +# frozen_string_literal: true + +require "monitor" + +module ActiveSupport + module Concurrency + # A monitor that will permit dependency loading while blocked waiting for + # the lock. + class LoadInterlockAwareMonitor < Monitor + # Enters an exclusive section, but allows dependency loading while blocked + def mon_enter + mon_try_enter || + ActiveSupport::Dependencies.interlock.permit_concurrent_loads { super } + end + end + end +end -- cgit v1.2.3