MB-45378: Fix static init fiasco with ExecutorPool & GoogleLog

When converting platform to be statically linked, a crash is seen
during shutdown of ep-engine_ep_unit_tests.DcpConnMapTest tests on
MSVC. The ExecutorPool is consuming messages on the background threads
(I believe to coordinate shutdown), and during that it attempts to log
a warning message to Google Log.

The cause of the crash is a change in the static initialisation (and
deinitialization) order - the GoogleLog singleton instance as used
internally by Folly is deinitialized before ExecutorPool singleton. As
such, when the ExecutorPool singleton is shutting down, it attempts to
log a message to a non-existant GLog instance and a nullptr is
deferenced.

Fix by changing ExecutorPool singleton to use C++11 magic static
(Meyer singleton); which ensures it is destructed earlier, before
GLog.

Additionally, while the above is sufficient to fix this issue on macOS
Catalina, on Mojave this introduces _another_ crash as some Folly
hazard pointer singletons appear to already have been destructed and
the following crash is seen:

    * thread #1, queue = 'com.apple.main-thread', stop reason = signal SIGABRT
      * frame #0: 0x00007fff7412f2c6 libsystem_kernel.dylib`__pthread_kill + 10
        frame #1: 0x00007fff741eabf1 libsystem_pthread.dylib`pthread_kill + 284
        frame #2: 0x00007fff740996a6 libsystem_c.dylib`abort + 127
        frame #3: 0x00007fff741a8077 libsystem_malloc.dylib`malloc_vreport + 545
        frame #4: 0x00007fff741a7e38 libsystem_malloc.dylib`malloc_report + 151
        frame #5: 0x00007fff73ff3cf9 libdyld.dylib`_tlv_atexit + 155
        frame #6: 0x000000010143cb2d ep-engine_ep_unit_tests`folly::SingletonThreadLocal<folly::hazptr_tc<std::__1::atomic>, folly::hazptr_tc_tls_tag, folly::detail::DefaultMake<folly::hazptr_tc<std::__1::atomic> >, folly::hazptr_tc_tls_tag>::getSlow(cache=0x000000010b5606b8) at SingletonThreadLocal.h:157 [opt]
        frame #7: 0x0000000101437a19 ep-engine_ep_unit_tests`folly::UnboundedBlockingQueue<folly::CPUThreadPoolExecutor::CPUTask>::add(folly::CPUThreadPoolExecutor::CPUTask) [inlined] folly::SingletonThreadLocal<folly::hazptr_tc<std::__1::atomic>, folly::hazptr_tc_tls_tag, folly::detail::DefaultMake<folly::hazptr_tc<std::__1::atomic> >, folly::hazptr_tc_tls_tag>::get() at SingletonThreadLocal.h:167 [opt]
        frame #8: 0x0000000101437a08 ep-engine_ep_unit_tests`folly::UnboundedBlockingQueue<folly::CPUThreadPoolExecutor::CPUTask>::add(folly::CPUThreadPoolExecutor::CPUTask) [inlined] folly::hazptr_tc<std::__1::atomic>& folly::hazptr_tc_tls<std::__1::atomic>() at HazptrThrLocal.h:166 [opt]
        frame #9: 0x0000000101437a08 ep-engine_ep_unit_tests`folly::UnboundedBlockingQueue<folly::CPUThreadPoolExecutor::CPUTask>::add(folly::CPUThreadPoolExecutor::CPUTask) at HazptrHolder.h:64 [opt]
        frame #10: 0x0000000101437a08 ep-engine_ep_unit_tests`folly::UnboundedBlockingQueue<folly::CPUThreadPoolExecutor::CPUTask>::add(folly::CPUThreadPoolExecutor::CPUTask) [inlined] folly::hazptr_holder<std::__1::atomic>::hazptr_holder(this=<unavailable>, domain=<unavailable>) at HazptrHolder.h:61 [opt]
        frame #11: 0x0000000101437a08 ep-engine_ep_unit_tests`folly::UnboundedBlockingQueue<folly::CPUThreadPoolExecutor::CPUTask>::add(folly::CPUThreadPoolExecutor::CPUTask) at UnboundedQueue.h:374 [opt]
        frame #12: 0x00000001014379e7 ep-engine_ep_unit_tests`folly::UnboundedBlockingQueue<folly::CPUThreadPoolExecutor::CPUTask>::add(folly::CPUThreadPoolExecutor::CPUTask) [inlined] folly::UnboundedQueue<folly::CPUThreadPoolExecutor::CPUTask, false, false, false, 6ul, 7ul, std::__1::atomic>::enqueue(this=0x00007ffeefbff770, arg=0x00007ffeefbff690) at UnboundedQueue.h:271 [opt]
        frame #13: 0x00000001014379e7 ep-engine_ep_unit_tests`folly::UnboundedBlockingQueue<folly::CPUThreadPoolExecutor::CPUTask>::add(this=0x000000010ba00f80, item=CPUTask @ 0x00007ffeefbff690) at UnboundedBlockingQueue.h:31 [opt]
        frame #14: 0x0000000101437bfc ep-engine_ep_unit_tests`folly::BlockingQueue<folly::CPUThreadPoolExecutor::CPUTask>::addWithPriority(this=0x000000010ba00f80, item=CPUTask @ 0x00007ffeefbff770, (null)=<unavailable>) at BlockingQueue.h:57 [opt]
        frame #15: 0x0000000101436b00 ep-engine_ep_unit_tests`folly::CPUThreadPoolExecutor::stopThreads(this=0x000000010bf8de00, n=2) at CPUThreadPoolExecutor.cpp:281 [opt]
        frame #16: 0x000000010144bae3 ep-engine_ep_unit_tests`folly::ThreadPoolExecutor::stop() [inlined] folly::ThreadPoolExecutor::removeThreads(this=<unavailable>, n=<unavailable>) at ThreadPoolExecutor.cpp:233 [opt]
        frame #17: 0x000000010144bad0 ep-engine_ep_unit_tests`folly::ThreadPoolExecutor::stop(this=0x000000010bf8de00) at ThreadPoolExecutor.cpp:251 [opt]
        frame #18: 0x00000001014352d4 ep-engine_ep_unit_tests`folly::CPUThreadPoolExecutor::~CPUThreadPoolExecutor(this=0x000000010bf8de00, vtt=0x00000001019fd6c8) at CPUThreadPoolExecutor.cpp:126 [opt]
        frame #19: 0x0000000101435465 ep-engine_ep_unit_tests`folly::CPUThreadPoolExecutor::~CPUThreadPoolExecutor() [inlined] folly::CPUThreadPoolExecutor::~CPUThreadPoolExecutor(this=0x000000010bf8de00) at CPUThreadPoolExecutor.cpp:124 [opt]
        frame #20: 0x0000000101435459 ep-engine_ep_unit_tests`folly::CPUThreadPoolExecutor::~CPUThreadPoolExecutor(this=0x000000010bf8de00) at CPUThreadPoolExecutor.cpp:124 [opt]
        frame #21: 0x000000010023240a ep-engine_ep_unit_tests`FollyExecutorPool::~FollyExecutorPool(this=0x000000010b7eed40) at folly_executorpool.cc:757 [opt]
        frame #22: 0x00000001002325ee ep-engine_ep_unit_tests`FollyExecutorPool::~FollyExecutorPool(this=0x000000010b7eed40) at folly_executorpool.cc:751 [opt]
        frame #23: 0x00007fff7409a3cf libsystem_c.dylib`__cxa_finalize_ranges + 319
        frame #24: 0x00007fff7409a6b3 libsystem_c.dylib`exit + 55

Address _this_ with a somewhat belt-and-braces approach - also
manually shutdown the ExecutorPool in DcpConnMapTest::TearDown - as is
done in other tests.

Change-Id: I87f13bc3a7cdf616b52d18502dd724fcf630d3b9
Reviewed-on: http://review.couchbase.org/c/kv_engine/+/152230
Tested-by: Build Bot <[email protected]>
Reviewed-by: Richard de Mellow <[email protected]>
Reviewed-by: Trond Norbye <[email protected]>

engines/ep/src/executorpool.cc

@@ -17,18 +17,17 @@
 #include "objectregistry.h"
 
 std::mutex ExecutorPool::initGuard;
-std::atomic<ExecutorPool*> ExecutorPool::instance;
 
 static const size_t EP_MIN_NONIO_THREADS = 2;
 
 static const size_t EP_MAX_AUXIO_THREADS = 8;
 static const size_t EP_MAX_NONIO_THREADS = 8;
 
 ExecutorPool *ExecutorPool::get() {
- auto* tmp = instance.load();
+ auto* tmp = getInstance().get();
  if (tmp == nullptr) {
  LockHolder lh(initGuard);
- tmp = instance.load();
+ tmp = getInstance().get();
  if (tmp == nullptr) {
  // Double-checked locking if instance is null - ensure two threads
  // don't both create an instance.
@@ -58,20 +57,16 @@ ExecutorPool *ExecutorPool::get() {
  "ExecutorPool::get() Invalid executor_pool_backend '" +
  config.getExecutorPoolBackend() + "'");
  }
- instance.store(tmp);
+ getInstance().reset(tmp);
  }
  }
  return tmp;
 }
 
 void ExecutorPool::shutdown() {
  std::lock_guard<std::mutex> lock(initGuard);
- auto* tmp = instance.load();
- if (tmp != nullptr) {
- NonBucketAllocationGuard guard;
- delete tmp;
- instance = nullptr;
- }
+ NonBucketAllocationGuard guard;
+ getInstance().reset();
 }
 
 ExecutorPool::ExecutorPool(size_t maxThreads)
@@ -213,3 +208,8 @@ int ExecutorPool::getThreadPriority(task_type_t taskType) {
 #endif
  return 0;
 }
+
+std::unique_ptr<ExecutorPool>& ExecutorPool::getInstance() {
+ static std::unique_ptr<ExecutorPool> instance;
+ return instance;
+}

engines/ep/src/executorpool.h

@@ -219,9 +219,11 @@ class ExecutorPool {
  */
  size_t calcNumNonIO(size_t threadCount) const;
 
+ // Return a reference to the singleton ExecutorPool.
+ static std::unique_ptr<ExecutorPool>& getInstance();
+
  // Singleton creation
  static std::mutex initGuard;
- static std::atomic<ExecutorPool*> instance;
 
  /**
  * Maximum number of threads of any given class (Reader, Writer, AuxIO,

engines/ep/src/fakes/fake_executorpool.h

@@ -29,6 +29,8 @@
 
 #include <folly/portability/GTest.h>
 
+#include <memory>
+
 class SingleThreadedExecutorPool : public CB3ExecutorPool {
 public:
 
@@ -39,17 +41,16 @@ class SingleThreadedExecutorPool : public CB3ExecutorPool {
  */
  static void replaceExecutorPoolWithFake() {
  LockHolder lh(initGuard);
- auto* tmp = instance.load();
- if (tmp != nullptr) {
+ auto& instance = getInstance();
+ if (instance) {
  throw std::runtime_error("replaceExecutorPoolWithFake: "
  "ExecutorPool instance already created - cowardly refusing to continue!");
  }
 
  EventuallyPersistentEngine *epe =
  ObjectRegistry::onSwitchThread(nullptr, true);
- tmp = new SingleThreadedExecutorPool();
+ instance = std::make_unique<SingleThreadedExecutorPool>();
  ObjectRegistry::onSwitchThread(epe);
- instance.store(tmp);
  }
 
  explicit SingleThreadedExecutorPool()

engines/ep/tests/mock/mock_executor_pool.cc

@@ -10,19 +10,20 @@
  */
 
 #include "mock_executor_pool.h"
+
 #include "objectregistry.h"
 #include "taskqueue.h"
+#include <memory>
 
 void MockExecutorPool::replaceExecutorPoolWithMock() {
  LockHolder lh(initGuard);
- auto* executor = instance.load();
+ auto& executor = getInstance();
  if (executor) {
  executor->shutdown();
  }
  auto* epEngine = ObjectRegistry::onSwitchThread(nullptr, true);
- executor = new MockExecutorPool();
+ executor = std::make_unique<MockExecutorPool>();
  ObjectRegistry::onSwitchThread(epEngine);
- instance.store(executor);
 }
 
 bool MockExecutorPool::isTaskScheduled(const task_type_t queueType,

engines/ep/tests/module_tests/dcp_test.cc

@@ -1700,7 +1700,9 @@ class DcpConnMapTest : public ::testing::Test {
  }
 
  void TearDown() override {
+ engine.reset();
  ObjectRegistry::onSwitchThread(nullptr);
+ ExecutorPool::shutdown();
  }
 
  /**