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author | Matthew Draper <matthew@trebex.net> | 2017-11-18 00:25:52 +1030 |
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committer | GitHub <noreply@github.com> | 2017-11-18 00:25:52 +1030 |
commit | 56c1326abb11ed275f04b6e0592ca66975e37f24 (patch) | |
tree | 6a7718a66d73d0369a33caeb4b4cdd87c44ebbad | |
parent | eed3d3fff5ca6be00b2fe0fe020bd025ddbabbd5 (diff) | |
parent | 1f9f6f6cfc57020ccb35f77872c56f069f337075 (diff) | |
download | rails-56c1326abb11ed275f04b6e0592ca66975e37f24.tar.gz rails-56c1326abb11ed275f04b6e0592ca66975e37f24.tar.bz2 rails-56c1326abb11ed275f04b6e0592ca66975e37f24.zip |
Merge pull request #31035 from BrentWheeldon/bmw-db-load-deadlock
Prevent deadlocks with load interlock and DB lock.
3 files changed, 74 insertions, 1 deletions
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb index 345983a655..7e6db860dd 100644 --- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb +++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb @@ -5,6 +5,7 @@ require "active_record/connection_adapters/schema_cache" require "active_record/connection_adapters/sql_type_metadata" require "active_record/connection_adapters/abstract/schema_dumper" require "active_record/connection_adapters/abstract/schema_creation" +require "active_support/concurrency/load_interlock_aware_monitor" require "arel/collectors/bind" require "arel/collectors/composite" require "arel/collectors/sql_string" @@ -107,7 +108,7 @@ module ActiveRecord @schema_cache = SchemaCache.new self @quoted_column_names, @quoted_table_names = {}, {} @visitor = arel_visitor - @lock = Monitor.new + @lock = ActiveSupport::Concurrency::LoadInterlockAwareMonitor.new if self.class.type_cast_config_to_boolean(config.fetch(:prepared_statements) { true }) @prepared_statements = true 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 diff --git a/activesupport/test/concurrency/load_interlock_aware_monitor_test.rb b/activesupport/test/concurrency/load_interlock_aware_monitor_test.rb new file mode 100644 index 0000000000..2d0f45ec5f --- /dev/null +++ b/activesupport/test/concurrency/load_interlock_aware_monitor_test.rb @@ -0,0 +1,55 @@ +# frozen_string_literal: true + +require "abstract_unit" +require "concurrent/atomic/count_down_latch" +require "active_support/concurrency/load_interlock_aware_monitor" + +module ActiveSupport + module Concurrency + class LoadInterlockAwareMonitorTest < ActiveSupport::TestCase + def setup + @monitor = ActiveSupport::Concurrency::LoadInterlockAwareMonitor.new + end + + def test_entering_with_no_blocking + assert @monitor.mon_enter + end + + def test_entering_with_blocking + load_interlock_latch = Concurrent::CountDownLatch.new + monitor_latch = Concurrent::CountDownLatch.new + + able_to_use_monitor = false + able_to_load = false + + thread_with_load_interlock = Thread.new do + ActiveSupport::Dependencies.interlock.running do + load_interlock_latch.count_down + monitor_latch.wait + + @monitor.synchronize do + able_to_use_monitor = true + end + end + end + + thread_with_monitor_lock = Thread.new do + @monitor.synchronize do + monitor_latch.count_down + load_interlock_latch.wait + + ActiveSupport::Dependencies.interlock.loading do + able_to_load = true + end + end + end + + thread_with_load_interlock.join + thread_with_monitor_lock.join + + assert able_to_use_monitor + assert able_to_load + end + end + end +end |