diff options
Diffstat (limited to 'activesupport/test/share_lock_test.rb')
| -rw-r--r-- | activesupport/test/share_lock_test.rb | 578 |
1 files changed, 578 insertions, 0 deletions
diff --git a/activesupport/test/share_lock_test.rb b/activesupport/test/share_lock_test.rb new file mode 100644 index 0000000000..30a1ddad3f --- /dev/null +++ b/activesupport/test/share_lock_test.rb @@ -0,0 +1,578 @@ +# frozen_string_literal: true + +require "abstract_unit" +require "concurrent/atomic/count_down_latch" +require "active_support/concurrency/share_lock" + +class ShareLockTest < ActiveSupport::TestCase + def setup + @lock = ActiveSupport::Concurrency::ShareLock.new + end + + def test_reentrancy + thread = Thread.new do + @lock.sharing { @lock.sharing { } } + @lock.exclusive { @lock.exclusive { } } + end + assert_threads_not_stuck thread + end + + def test_sharing_doesnt_block + with_thread_waiting_in_lock_section(:sharing) do |sharing_thread_latch| + assert_threads_not_stuck(Thread.new { @lock.sharing { } }) + end + end + + def test_sharing_blocks_exclusive + with_thread_waiting_in_lock_section(:sharing) do |sharing_thread_release_latch| + @lock.exclusive(no_wait: true) { flunk } # polling should fail + exclusive_thread = Thread.new { @lock.exclusive { } } + assert_threads_stuck_but_releasable_by_latch exclusive_thread, sharing_thread_release_latch + end + end + + def test_exclusive_blocks_sharing + with_thread_waiting_in_lock_section(:exclusive) do |exclusive_thread_release_latch| + sharing_thread = Thread.new { @lock.sharing { } } + assert_threads_stuck_but_releasable_by_latch sharing_thread, exclusive_thread_release_latch + end + end + + def test_multiple_exlusives_are_able_to_progress + with_thread_waiting_in_lock_section(:sharing) do |sharing_thread_release_latch| + exclusive_threads = (1..2).map do + Thread.new do + @lock.exclusive { } + end + end + + assert_threads_stuck_but_releasable_by_latch exclusive_threads, sharing_thread_release_latch + end + end + + def test_sharing_is_upgradeable_to_exclusive + upgrading_thread = Thread.new do + @lock.sharing do + @lock.exclusive { } + end + end + assert_threads_not_stuck upgrading_thread + end + + def test_exclusive_upgrade_waits_for_other_sharers_to_leave + with_thread_waiting_in_lock_section(:sharing) do |sharing_thread_release_latch| + in_sharing = Concurrent::CountDownLatch.new + + upgrading_thread = Thread.new do + @lock.sharing do + in_sharing.count_down + @lock.exclusive { } + end + end + + in_sharing.wait + assert_threads_stuck_but_releasable_by_latch upgrading_thread, sharing_thread_release_latch + end + end + + def test_exclusive_matching_purpose + [true, false].each do |use_upgrading| + with_thread_waiting_in_lock_section(:sharing) do |sharing_thread_release_latch| + exclusive_threads = (1..2).map do + Thread.new do + @lock.send(use_upgrading ? :sharing : :tap) do + @lock.exclusive(purpose: :load, compatible: [:load, :unload]) { } + end + end + end + + assert_threads_stuck_but_releasable_by_latch exclusive_threads, sharing_thread_release_latch + end + end + end + + def test_killed_thread_loses_lock + with_thread_waiting_in_lock_section(:sharing) do |sharing_thread_release_latch| + thread = Thread.new do + @lock.sharing do + @lock.exclusive { } + end + end + + assert_threads_stuck thread + thread.kill + + sharing_thread_release_latch.count_down + + thread = Thread.new do + @lock.exclusive { } + end + + assert_threads_not_stuck thread + end + end + + def test_exclusive_conflicting_purpose + [true, false].each do |use_upgrading| + with_thread_waiting_in_lock_section(:sharing) do |sharing_thread_release_latch| + together = Concurrent::CyclicBarrier.new(2) + conflicting_exclusive_threads = [ + Thread.new do + @lock.send(use_upgrading ? :sharing : :tap) do + together.wait + @lock.exclusive(purpose: :red, compatible: [:green, :purple]) { } + end + end, + Thread.new do + @lock.send(use_upgrading ? :sharing : :tap) do + together.wait + @lock.exclusive(purpose: :blue, compatible: [:green]) { } + end + end + ] + + assert_threads_stuck conflicting_exclusive_threads # wait for threads to get into their respective `exclusive {}` blocks + + # This thread will be stuck as long as any other thread is in + # a sharing block. While it's blocked, it holds no lock, so it + # doesn't interfere with any other attempts. + no_purpose_thread = Thread.new do + @lock.exclusive { } + end + assert_threads_stuck no_purpose_thread + + # This thread is compatible with both of the "primary" + # attempts above. It's initially stuck on the outer share + # lock, but as soon as that's released, it can run -- + # regardless of whether those threads hold share locks. + compatible_thread = Thread.new do + @lock.exclusive(purpose: :green, compatible: []) { } + end + assert_threads_stuck compatible_thread + + assert_threads_stuck conflicting_exclusive_threads + + sharing_thread_release_latch.count_down + + assert_threads_not_stuck compatible_thread # compatible thread is now able to squeak through + + if use_upgrading + # The "primary" threads both each hold a share lock, and are + # mutually incompatible; they're still stuck. + assert_threads_stuck conflicting_exclusive_threads + + # The thread without a specified purpose is also stuck; it's + # not compatible with anything. + assert_threads_stuck no_purpose_thread + else + # As the primaries didn't hold a share lock, as soon as the + # outer one was released, all the exclusive locks are free + # to be acquired in turn. + + assert_threads_not_stuck conflicting_exclusive_threads + assert_threads_not_stuck no_purpose_thread + end + ensure + conflicting_exclusive_threads.each(&:kill) + no_purpose_thread.kill + end + end + end + + def test_exclusive_ordering + scratch_pad = [] + scratch_pad_mutex = Mutex.new + + load_params = [:load, [:load]] + unload_params = [:unload, [:unload, :load]] + + all_sharing = Concurrent::CyclicBarrier.new(4) + + [load_params, load_params, unload_params, unload_params].permutation do |thread_params| + with_thread_waiting_in_lock_section(:sharing) do |sharing_thread_release_latch| + threads = thread_params.map do |purpose, compatible| + Thread.new do + @lock.sharing do + all_sharing.wait + @lock.exclusive(purpose: purpose, compatible: compatible) do + scratch_pad_mutex.synchronize { scratch_pad << purpose } + end + end + end + end + + sleep(0.01) + scratch_pad_mutex.synchronize { assert_empty scratch_pad } + + sharing_thread_release_latch.count_down + + assert_threads_not_stuck threads + scratch_pad_mutex.synchronize do + assert_equal [:load, :load, :unload, :unload], scratch_pad + scratch_pad.clear + end + end + end + end + + def test_new_share_attempts_block_on_waiting_exclusive + with_thread_waiting_in_lock_section(:sharing) do |sharing_thread_release_latch| + release_exclusive = Concurrent::CountDownLatch.new + + waiting_exclusive = Thread.new do + @lock.sharing do + @lock.exclusive do + release_exclusive.wait + end + end + end + assert_threads_stuck waiting_exclusive + + late_share_attempt = Thread.new do + @lock.sharing { } + end + assert_threads_stuck late_share_attempt + + sharing_thread_release_latch.count_down + assert_threads_stuck late_share_attempt + + release_exclusive.count_down + assert_threads_not_stuck late_share_attempt + end + end + + def test_share_remains_reentrant_ignoring_a_waiting_exclusive + with_thread_waiting_in_lock_section(:sharing) do |sharing_thread_release_latch| + ready = Concurrent::CyclicBarrier.new(2) + attempt_reentrancy = Concurrent::CountDownLatch.new + + sharer = Thread.new do + @lock.sharing do + ready.wait + attempt_reentrancy.wait + @lock.sharing { } + end + end + + exclusive = Thread.new do + @lock.sharing do + ready.wait + @lock.exclusive { } + end + end + + assert_threads_stuck exclusive + + attempt_reentrancy.count_down + + assert_threads_not_stuck sharer + assert_threads_stuck exclusive + end + end + + def test_compatible_exclusives_cooperate_to_both_proceed + ready = Concurrent::CyclicBarrier.new(2) + done = Concurrent::CyclicBarrier.new(2) + + threads = 2.times.map do + Thread.new do + @lock.sharing do + ready.wait + @lock.exclusive(purpose: :x, compatible: [:x], after_compatible: [:x]) { } + done.wait + end + end + end + + assert_threads_not_stuck threads + end + + def test_manual_yield + ready = Concurrent::CyclicBarrier.new(2) + done = Concurrent::CyclicBarrier.new(2) + + threads = [ + Thread.new do + @lock.sharing do + ready.wait + @lock.exclusive(purpose: :x) { } + done.wait + end + end, + + Thread.new do + @lock.sharing do + ready.wait + @lock.yield_shares(compatible: [:x]) do + done.wait + end + end + end, + ] + + assert_threads_not_stuck threads + end + + def test_manual_incompatible_yield + ready = Concurrent::CyclicBarrier.new(2) + done = Concurrent::CyclicBarrier.new(2) + + threads = [ + Thread.new do + @lock.sharing do + ready.wait + @lock.exclusive(purpose: :x) { } + done.wait + end + end, + + Thread.new do + @lock.sharing do + ready.wait + @lock.yield_shares(compatible: [:y]) do + done.wait + end + end + end, + ] + + assert_threads_stuck threads + ensure + threads.each(&:kill) if threads + end + + def test_manual_recursive_yield + ready = Concurrent::CyclicBarrier.new(2) + done = Concurrent::CyclicBarrier.new(2) + do_nesting = Concurrent::CountDownLatch.new + + threads = [ + Thread.new do + @lock.sharing do + ready.wait + @lock.exclusive(purpose: :x) { } + done.wait + end + end, + + Thread.new do + @lock.sharing do + @lock.yield_shares(compatible: [:x]) do + @lock.sharing do + ready.wait + do_nesting.wait + @lock.yield_shares(compatible: [:x, :y]) do + done.wait + end + end + end + end + end + ] + + assert_threads_stuck threads + do_nesting.count_down + + assert_threads_not_stuck threads + end + + def test_manual_recursive_yield_cannot_expand_outer_compatible + ready = Concurrent::CyclicBarrier.new(2) + do_compatible_nesting = Concurrent::CountDownLatch.new + in_compatible_nesting = Concurrent::CountDownLatch.new + + incompatible_thread = Thread.new do + @lock.sharing do + ready.wait + @lock.exclusive(purpose: :x) { } + end + end + + yield_shares_thread = Thread.new do + @lock.sharing do + ready.wait + @lock.yield_shares(compatible: [:y]) do + do_compatible_nesting.wait + @lock.sharing do + @lock.yield_shares(compatible: [:x, :y]) do + in_compatible_nesting.wait + end + end + end + end + end + + assert_threads_stuck incompatible_thread + do_compatible_nesting.count_down + assert_threads_stuck incompatible_thread + in_compatible_nesting.count_down + assert_threads_not_stuck [yield_shares_thread, incompatible_thread] + end + + def test_manual_recursive_yield_restores_previous_compatible + ready = Concurrent::CyclicBarrier.new(2) + do_nesting = Concurrent::CountDownLatch.new + after_nesting = Concurrent::CountDownLatch.new + + incompatible_thread = Thread.new do + ready.wait + @lock.exclusive(purpose: :z) { } + end + + recursive_yield_shares_thread = Thread.new do + @lock.sharing do + ready.wait + @lock.yield_shares(compatible: [:y]) do + do_nesting.wait + @lock.sharing do + @lock.yield_shares(compatible: [:x, :y]) { } + end + after_nesting.wait + end + end + end + + assert_threads_stuck incompatible_thread + do_nesting.count_down + assert_threads_stuck incompatible_thread + + compatible_thread = Thread.new do + @lock.exclusive(purpose: :y) { } + end + assert_threads_not_stuck compatible_thread + + post_nesting_incompatible_thread = Thread.new do + @lock.exclusive(purpose: :x) { } + end + assert_threads_stuck post_nesting_incompatible_thread + + after_nesting.count_down + assert_threads_not_stuck recursive_yield_shares_thread + # post_nesting_incompatible_thread can now proceed + assert_threads_not_stuck post_nesting_incompatible_thread + # assert_threads_not_stuck can now proceed + assert_threads_not_stuck incompatible_thread + end + + def test_in_shared_section_incompatible_non_upgrading_threads_cannot_preempt_upgrading_threads + scratch_pad = [] + scratch_pad_mutex = Mutex.new + + upgrading_load_params = [:load, [:load], true] + non_upgrading_unload_params = [:unload, [:load, :unload], false] + + [upgrading_load_params, non_upgrading_unload_params].permutation do |thread_params| + with_thread_waiting_in_lock_section(:sharing) do |sharing_thread_release_latch| + threads = thread_params.map do |purpose, compatible, use_upgrading| + Thread.new do + @lock.send(use_upgrading ? :sharing : :tap) do + @lock.exclusive(purpose: purpose, compatible: compatible) do + scratch_pad_mutex.synchronize { scratch_pad << purpose } + end + end + end + end + + assert_threads_stuck threads + scratch_pad_mutex.synchronize { assert_empty scratch_pad } + + sharing_thread_release_latch.count_down + + assert_threads_not_stuck threads + scratch_pad_mutex.synchronize do + assert_equal [:load, :unload], scratch_pad + scratch_pad.clear + end + end + end + end + + private + + module CustomAssertions + SUFFICIENT_TIMEOUT = 0.2 + + private + + def assert_threads_stuck_but_releasable_by_latch(threads, latch) + assert_threads_stuck threads + latch.count_down + assert_threads_not_stuck threads + end + + def assert_threads_stuck(threads) + sleep(SUFFICIENT_TIMEOUT) # give threads time to do their business + assert(Array(threads).all? { |t| t.join(0.001).nil? }) + end + + def assert_threads_not_stuck(threads) + assert(Array(threads).all? { |t| t.join(SUFFICIENT_TIMEOUT) }) + end + end + + class CustomAssertionsTest < ActiveSupport::TestCase + include CustomAssertions + + def setup + @latch = Concurrent::CountDownLatch.new + @thread = Thread.new { @latch.wait } + end + + def teardown + @latch.count_down + @thread.join + end + + def test_happy_path + assert_threads_stuck_but_releasable_by_latch @thread, @latch + end + + def test_detects_stuck_thread + assert_raises(Minitest::Assertion) do + assert_threads_not_stuck @thread + end + end + + def test_detects_free_thread + @latch.count_down + assert_raises(Minitest::Assertion) do + assert_threads_stuck @thread + end + end + + def test_detects_already_released + @latch.count_down + assert_raises(Minitest::Assertion) do + assert_threads_stuck_but_releasable_by_latch @thread, @latch + end + end + + def test_detects_remains_latched + another_latch = Concurrent::CountDownLatch.new + assert_raises(Minitest::Assertion) do + assert_threads_stuck_but_releasable_by_latch @thread, another_latch + end + end + end + + include CustomAssertions + + def with_thread_waiting_in_lock_section(lock_section) + in_section = Concurrent::CountDownLatch.new + section_release = Concurrent::CountDownLatch.new + + stuck_thread = Thread.new do + @lock.send(lock_section) do + in_section.count_down + section_release.wait + end + end + + in_section.wait + + yield section_release + ensure + section_release.count_down + stuck_thread.join # clean up + end +end |