diff options
author | misterg <misterg@google.com> | 2017-09-19T20·54-0400 |
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committer | misterg <misterg@google.com> | 2017-09-19T20·54-0400 |
commit | c2e754829628d1e9b7a16b3389cfdace76950fdf (patch) | |
tree | 5a7f056f44e27c30e10025113b644f0b3b5801fc /absl/base/spinlock_test_common.cc |
Initial Commit
Diffstat (limited to 'absl/base/spinlock_test_common.cc')
-rw-r--r-- | absl/base/spinlock_test_common.cc | 265 |
1 files changed, 265 insertions, 0 deletions
diff --git a/absl/base/spinlock_test_common.cc b/absl/base/spinlock_test_common.cc new file mode 100644 index 000000000000..b1212eaf7e91 --- /dev/null +++ b/absl/base/spinlock_test_common.cc @@ -0,0 +1,265 @@ +// Copyright 2017 The Abseil Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +// A bunch of threads repeatedly hash an array of ints protected by a +// spinlock. If the spinlock is working properly, all elements of the +// array should be equal at the end of the test. + +#include <cstdint> +#include <limits> +#include <random> +#include <thread> // NOLINT(build/c++11) +#include <vector> + +#include "gtest/gtest.h" +#include "absl/base/internal/low_level_scheduling.h" +#include "absl/base/internal/spinlock.h" +#include "absl/base/internal/sysinfo.h" +#include "absl/synchronization/blocking_counter.h" +#include "absl/synchronization/notification.h" + +constexpr int32_t kNumThreads = 10; +constexpr int32_t kIters = 1000; + +namespace absl { +namespace base_internal { + +// This is defined outside of anonymous namespace so that it can be +// a friend of SpinLock to access protected methods for testing. +struct SpinLockTest { + static uint32_t EncodeWaitCycles(int64_t wait_start_time, + int64_t wait_end_time) { + return SpinLock::EncodeWaitCycles(wait_start_time, wait_end_time); + } + static uint64_t DecodeWaitCycles(uint32_t lock_value) { + return SpinLock::DecodeWaitCycles(lock_value); + } +}; + +namespace { + +static constexpr int kArrayLength = 10; +static uint32_t values[kArrayLength]; + +static SpinLock static_spinlock(base_internal::kLinkerInitialized); +static SpinLock static_cooperative_spinlock( + base_internal::kLinkerInitialized, + base_internal::SCHEDULE_COOPERATIVE_AND_KERNEL); +static SpinLock static_noncooperative_spinlock( + base_internal::kLinkerInitialized, base_internal::SCHEDULE_KERNEL_ONLY); + +// Simple integer hash function based on the public domain lookup2 hash. +// http://burtleburtle.net/bob/c/lookup2.c +static uint32_t Hash32(uint32_t a, uint32_t c) { + uint32_t b = 0x9e3779b9UL; // The golden ratio; an arbitrary value. + a -= b; a -= c; a ^= (c >> 13); + b -= c; b -= a; b ^= (a << 8); + c -= a; c -= b; c ^= (b >> 13); + a -= b; a -= c; a ^= (c >> 12); + b -= c; b -= a; b ^= (a << 16); + c -= a; c -= b; c ^= (b >> 5); + a -= b; a -= c; a ^= (c >> 3); + b -= c; b -= a; b ^= (a << 10); + c -= a; c -= b; c ^= (b >> 15); + return c; +} + +static void TestFunction(int thread_salt, SpinLock* spinlock) { + for (int i = 0; i < kIters; i++) { + SpinLockHolder h(spinlock); + for (int j = 0; j < kArrayLength; j++) { + const int index = (j + thread_salt) % kArrayLength; + values[index] = Hash32(values[index], thread_salt); + std::this_thread::yield(); + } + } +} + +static void ThreadedTest(SpinLock* spinlock) { + std::vector<std::thread> threads; + for (int i = 0; i < kNumThreads; ++i) { + threads.push_back(std::thread(TestFunction, i, spinlock)); + } + for (auto& thread : threads) { + thread.join(); + } + + SpinLockHolder h(spinlock); + for (int i = 1; i < kArrayLength; i++) { + EXPECT_EQ(values[0], values[i]); + } +} + +TEST(SpinLock, StackNonCooperativeDisablesScheduling) { + SpinLock spinlock(base_internal::SCHEDULE_KERNEL_ONLY); + spinlock.Lock(); + EXPECT_FALSE(base_internal::SchedulingGuard::ReschedulingIsAllowed()); + spinlock.Unlock(); +} + +TEST(SpinLock, StaticNonCooperativeDisablesScheduling) { + static_noncooperative_spinlock.Lock(); + EXPECT_FALSE(base_internal::SchedulingGuard::ReschedulingIsAllowed()); + static_noncooperative_spinlock.Unlock(); +} + +TEST(SpinLock, WaitCyclesEncoding) { + // These are implementation details not exported by SpinLock. + const int kProfileTimestampShift = 7; + const int kLockwordReservedShift = 3; + const uint32_t kSpinLockSleeper = 8; + + // We should be able to encode up to (1^kMaxCycleBits - 1) without clamping + // but the lower kProfileTimestampShift will be dropped. + const int kMaxCyclesShift = + 32 - kLockwordReservedShift + kProfileTimestampShift; + const uint64_t kMaxCycles = (int64_t{1} << kMaxCyclesShift) - 1; + + // These bits should be zero after encoding. + const uint32_t kLockwordReservedMask = (1 << kLockwordReservedShift) - 1; + + // These bits are dropped when wait cycles are encoded. + const uint64_t kProfileTimestampMask = (1 << kProfileTimestampShift) - 1; + + // Test a bunch of random values + std::default_random_engine generator; + // Shift to avoid overflow below. + std::uniform_int_distribution<uint64_t> time_distribution( + 0, std::numeric_limits<uint64_t>::max() >> 4); + std::uniform_int_distribution<uint64_t> cycle_distribution(0, kMaxCycles); + + for (int i = 0; i < 100; i++) { + int64_t start_time = time_distribution(generator); + int64_t cycles = cycle_distribution(generator); + int64_t end_time = start_time + cycles; + uint32_t lock_value = SpinLockTest::EncodeWaitCycles(start_time, end_time); + EXPECT_EQ(0, lock_value & kLockwordReservedMask); + uint64_t decoded = SpinLockTest::DecodeWaitCycles(lock_value); + EXPECT_EQ(0, decoded & kProfileTimestampMask); + EXPECT_EQ(cycles & ~kProfileTimestampMask, decoded); + } + + // Test corner cases + int64_t start_time = time_distribution(generator); + EXPECT_EQ(0, SpinLockTest::EncodeWaitCycles(start_time, start_time)); + EXPECT_EQ(0, SpinLockTest::DecodeWaitCycles(0)); + EXPECT_EQ(0, SpinLockTest::DecodeWaitCycles(kLockwordReservedMask)); + EXPECT_EQ(kMaxCycles & ~kProfileTimestampMask, + SpinLockTest::DecodeWaitCycles(~kLockwordReservedMask)); + + // Check that we cannot produce kSpinLockSleeper during encoding. + int64_t sleeper_cycles = + kSpinLockSleeper << (kProfileTimestampShift - kLockwordReservedShift); + uint32_t sleeper_value = + SpinLockTest::EncodeWaitCycles(start_time, start_time + sleeper_cycles); + EXPECT_NE(sleeper_value, kSpinLockSleeper); + + // Test clamping + uint32_t max_value = + SpinLockTest::EncodeWaitCycles(start_time, start_time + kMaxCycles); + uint64_t max_value_decoded = SpinLockTest::DecodeWaitCycles(max_value); + uint64_t expected_max_value_decoded = kMaxCycles & ~kProfileTimestampMask; + EXPECT_EQ(expected_max_value_decoded, max_value_decoded); + + const int64_t step = (1 << kProfileTimestampShift); + uint32_t after_max_value = + SpinLockTest::EncodeWaitCycles(start_time, start_time + kMaxCycles + step); + uint64_t after_max_value_decoded = + SpinLockTest::DecodeWaitCycles(after_max_value); + EXPECT_EQ(expected_max_value_decoded, after_max_value_decoded); + + uint32_t before_max_value = SpinLockTest::EncodeWaitCycles( + start_time, start_time + kMaxCycles - step); + uint64_t before_max_value_decoded = + SpinLockTest::DecodeWaitCycles(before_max_value); + EXPECT_GT(expected_max_value_decoded, before_max_value_decoded); +} + +TEST(SpinLockWithThreads, StaticSpinLock) { + ThreadedTest(&static_spinlock); +} + +TEST(SpinLockWithThreads, StackSpinLock) { + SpinLock spinlock; + ThreadedTest(&spinlock); +} + +TEST(SpinLockWithThreads, StackCooperativeSpinLock) { + SpinLock spinlock(base_internal::SCHEDULE_COOPERATIVE_AND_KERNEL); + ThreadedTest(&spinlock); +} + +TEST(SpinLockWithThreads, StackNonCooperativeSpinLock) { + SpinLock spinlock(base_internal::SCHEDULE_KERNEL_ONLY); + ThreadedTest(&spinlock); +} + +TEST(SpinLockWithThreads, StaticCooperativeSpinLock) { + ThreadedTest(&static_cooperative_spinlock); +} + +TEST(SpinLockWithThreads, StaticNonCooperativeSpinLock) { + ThreadedTest(&static_noncooperative_spinlock); +} + +TEST(SpinLockWithThreads, DoesNotDeadlock) { + struct Helper { + static void NotifyThenLock(Notification* locked, SpinLock* spinlock, + BlockingCounter* b) { + locked->WaitForNotification(); // Wait for LockThenWait() to hold "s". + b->DecrementCount(); + SpinLockHolder l(spinlock); + } + + static void LockThenWait(Notification* locked, SpinLock* spinlock, + BlockingCounter* b) { + SpinLockHolder l(spinlock); + locked->Notify(); + b->Wait(); + } + + static void DeadlockTest(SpinLock* spinlock, int num_spinners) { + Notification locked; + BlockingCounter counter(num_spinners); + std::vector<std::thread> threads; + + threads.push_back( + std::thread(Helper::LockThenWait, &locked, spinlock, &counter)); + for (int i = 0; i < num_spinners; ++i) { + threads.push_back( + std::thread(Helper::NotifyThenLock, &locked, spinlock, &counter)); + } + + for (auto& thread : threads) { + thread.join(); + } + } + }; + + SpinLock stack_cooperative_spinlock( + base_internal::SCHEDULE_COOPERATIVE_AND_KERNEL); + SpinLock stack_noncooperative_spinlock(base_internal::SCHEDULE_KERNEL_ONLY); + Helper::DeadlockTest(&stack_cooperative_spinlock, + base_internal::NumCPUs() * 2); + Helper::DeadlockTest(&stack_noncooperative_spinlock, + base_internal::NumCPUs() * 2); + Helper::DeadlockTest(&static_cooperative_spinlock, + base_internal::NumCPUs() * 2); + Helper::DeadlockTest(&static_noncooperative_spinlock, + base_internal::NumCPUs() * 2); +} + +} // namespace +} // namespace base_internal +} // namespace absl |